# Publications

Below you can find the list of all publications by the members of the Antenna Group. Publications before 2016 can be found in the Archive.

[Last updated: June 17, 2018]

## Journal

201820172016
• M. Bodehou and C. Craeye, “Another Field Decomposition for the Transmittance between OAM Antennas,” Forum for Electromagnetic Research Methods and Application Technologies (FERMAT), vol. 24, pp. 1-7, 2017.

This paper first provides an intuitive description of the spectral representations for the transmittance between two apertures. Then, two spectral representations of the transmittance between OAM antennas are compared. The first one makes use of the Modified Zernike function and has already been described in a previous publication. The second one is based on the Fourier-Bessel decomposition of the current distribution on the apertures. Both families of expansion functions are orthogonal on a disk and admit a closed form spectrum. In both cases, the transmittance in the far-field can be approximated in closed form if the current distribution is expressed in the basis. However, it is observed that the far-field behavior is fundamentally different, highlighting the complementarity between the two bases.

``````@article{boreal:195112,
title = {Another Field Decomposition for the Transmittance between OAM Antennas},
author = {Bodehou, Modeste and Craeye, Christophe},
abstract = {This paper first provides an intuitive description of the spectral representations for the transmittance between two apertures. Then, two spectral representations of the transmittance between OAM antennas are compared. The first one makes use of the Modified Zernike function and has already been described in a previous publication. The second one is based on the Fourier-Bessel decomposition of the current distribution on the apertures. Both families of expansion functions are orthogonal on a disk and admit a closed form spectrum. In both cases, the transmittance in the far-field can be approximated in closed form if the current distribution is expressed in the basis. However, it is observed that the far-field behavior is fundamentally different, highlighting the complementarity between the two bases.},
Keywords = {OAM , aperture antennas , transmittance , multiplexing , spectral domain formulation.},
language = {Anglais},
journal = {Forum for Electromagnetic Research Methods and Application Technologies (FERMAT)},
volume = {24},
pages = {1-7},
issn = {2470-4202},
address = {319 Electrical Engineering East The Pennsylvania State University University Park, PA 16802},
publisher = {Raj Mittra},
year = {2017},
url = {http://hdl.handle.net/2078.1/195112}}``````

• J. I. Echeveste Guzman, G. M. A. de Aza, J. Rubio, and C. Craeye, “Gradient-based aperiodic array synthesis of real arrays with uniform amplitude excitation including mutual coupling,” IEEE Transactions on Antennas and Propagation, vol. 65, pp. 541-551, 2017. doi:10.1109/TAP.2016.2638359

This paper proposes the synthesis of aperiodic arrays of realistic antennas excited with uniform amplitude, where the mutual coupling between elements is rigorously taken into account. A cost function that involves the expression of the radiated field of the coupled array is obtained and its gradient is evaluated in order to move the elements in the corresponding direction at each iteration. The synthesis method involves the calculation of the gradient of the field radiated by the coupled array, which is obtained analytically by using a full-wave method based on the generalized scattering matrix, spherical mode expansions and rotation, and translation properties of spherical waves.

``````@article{boreal:194964,
title = {Gradient-based aperiodic array synthesis of real arrays with uniform amplitude excitation including mutual coupling},
author = {Echeveste Guzman, Jose Ignacio and M.A. Gonzalez de Aza and J. Rubio and Craeye, Christophe},
abstract = {This paper proposes the synthesis of aperiodic arrays of realistic antennas excited with uniform amplitude, where the mutual coupling between elements is rigorously taken into account. A cost function that involves the expression of the radiated field of the coupled array is obtained and its gradient is evaluated in order to move the elements in the corresponding direction at each iteration. The synthesis method involves the calculation of the gradient of the field radiated by the coupled array, which is obtained analytically by using a full-wave method based on the generalized scattering matrix, spherical mode expansions and rotation, and translation properties of spherical waves.},
Keywords = {Aperiodic arrays , array synthesis , gradient method , local optimization , mutual coupling , spherical waves},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {65},
pages = {541-551},
issn = {1558-2221},
doi = {10.1109/TAP.2016.2638359},
publisher = {I E E E},
year = {2017},
url = {http://hdl.handle.net/2078.1/194964}}``````

• T. Feuillen, T. Pairon, C. Craeye, and L. Vandendorpe, “Localization of Rotating Targets Using a Monochromatic Continuous-Wave Radar,” IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 2598-2601, 2017. doi:10.1109/LAWP.2017.2735020

A simple and efficient localization method for rotating objects is introduced. The estimation of the position is performed using only a continuous-wave radar with multiple receiving antennas. The method relies on the establishment of a linear relation between the interelement phase shifts and frequency, which is exploitable in the near-to-intermediate field. The method is introduced, and its independence with respect to the shape of the target demonstrated. Monte Carlo simulations are performed to study the variance of the proposed estimator. An experimental validation is carried out with a rotating cylinder and shows good agreement with simulations.

``````@article{boreal:189817,
title = {Localization of Rotating Targets Using a Monochromatic Continuous-Wave Radar},
author = {Feuillen, Thomas and Pairon, Thomas and Craeye, Christophe and Vandendorpe, Luc},
abstract = {A simple and efficient localization method for rotating objects is introduced. The estimation of the position is performed using only a continuous-wave radar with multiple receiving antennas. The method relies on the establishment of a linear relation between the interelement phase shifts and frequency, which is exploitable in the near-to-intermediate field. The method is introduced, and its independence with respect to the shape of the target demonstrated. Monte Carlo simulations are performed to study the variance of the proposed estimator. An experimental validation is carried out with a rotating cylinder and shows good agreement with simulations.},
Keywords = {Radar ,   Estimation ,   Radar antennas ,   Receiving antennas ,   Frequency modulation ,   Signal to noise ratio ,   Angular velocity},
language = {Anglais},
journal = {IEEE Antennas and Wireless Propagation Letters},
volume = {16},
pages = {2598 - 2601},
issn = {1548-5757},
doi = {10.1109/LAWP.2017.2735020},
publisher = {I E E E},
year = {2017},
url = {http://hdl.handle.net/2078.1/189817}}``````

• B. V. Ha, C. Craeye, and E. de Lera Acedo, “Main beam modeling for large irregular arrays : The SKA1-LOW telescope case,” Experimental Astronomy, vol. 44, pp. 239-258, 2017. doi:10.1007/s10686-017-9565-y

Large radio telescopes in the 21st century such as the Low-Frequency Array (LOFAR) or the Murchison Widefield Array (MWA) make use of phased aperture arrays of antennas to achieve superb survey speeds. The Square Kilometer Array low frequency instrument (SKA1-LOW) will consist of a collection of non-regular phased array systems. The prediction of the main beam of these arrays using a few coefficients is crucial for the calibration of the telescope. An effective approach to model the main beam and first few sidelobes for large non-regular arrays is presented. The approach exploits Zernike polynomials to represent the array pattern. Starting from the current defined on an equivalence plane located just above the array, the pattern is expressed as a sum of Fourier transforms of Zernike functions of different orders. The coefficients for Zernike polynomials are derived by two different means: least-squares and analytical approaches. The analysis shows that both approaches provide a similar performance for representing the main beam and first few sidelobes. Moreover, numerical results for different array configurations are provided, which demonstrate the performance of the proposed method, also for arrays with shapes far from circular. Main Beam Modeling for Large Irregular Arrays: The SKA1-LOW telescope case | Request PDF. Available from: https://www.researchgate.net/publication/317230276_Main_Beam_Modeling_for_Large_Irregular_Arrays_The_SKA1-LOW_telescope_case [accessed Jan 22 2018].

``````@article{boreal:193619,
title = {Main beam modeling for large irregular arrays : The SKA1-LOW telescope case},
author = {Bui Van Ha and Craeye, Christophe and de Lera Acedo, Eloy},
abstract = {Large radio telescopes in the 21st century such as the Low-Frequency Array (LOFAR) or the Murchison Widefield Array (MWA) make use of phased aperture arrays of antennas to achieve superb survey speeds. The Square Kilometer Array low frequency instrument (SKA1-LOW) will consist of a collection of non-regular phased array systems. The prediction of the main beam of these arrays using a few coefficients is crucial for the calibration of the telescope. An effective approach to model the main beam and first few sidelobes for large non-regular arrays is presented. The approach exploits Zernike polynomials to represent the array pattern. Starting from the current defined on an equivalence plane located just above the array, the pattern is expressed as a sum of Fourier transforms of Zernike functions of different orders. The coefficients for Zernike polynomials are derived by two different means: least-squares and analytical approaches. The analysis shows that both approaches provide a similar performance for representing the main beam and first few sidelobes. Moreover, numerical results for different array configurations are provided, which demonstrate the performance of the proposed method, also for arrays with shapes far from circular. Main Beam Modeling for Large Irregular Arrays: The SKA1-LOW telescope case | Request PDF. Available from: https://www.researchgate.net/publication/317230276_Main_Beam_Modeling_for_Large_Irregular_Arrays_The_SKA1-LOW_telescope_case [accessed Jan 22 2018].},
Keywords = {Space and Planetary Science , Astronomy and Astrophysics},
language = {Anglais},
journal = {Experimental Astronomy},
volume = {44},
pages = {239-258},
issn = {1572-9508},
doi = {10.1007/s10686-017-9565-y},
publisher = {Springer Nature},
year = {2017},
url = {http://hdl.handle.net/2078.1/193619}}``````

• C. Craeye, “On the transmittance between OAM antennas,” IEEE Transactions on Antennas and Propagation, vol. 64, iss. 1, pp. 336-339, 2017. doi:10.1109/TAP.2015.2500914

A quasi-analytical solution is derived for the transmittance between two OAM antennas. It makes use of the properties of the modified circle polynomials, related to Zernike functions, and of integration in the complex plane of the radial spectral coordinate. The resulting formulation can be estimated extremely fast and is shown to exhibit several expected properties. An asymptotic expression is proposed and validated.

``````@article{boreal:183213,
title = {On the transmittance between OAM antennas},
author = {Craeye, Christophe},
abstract = {A quasi-analytical solution is derived for the transmittance between two OAM antennas. It makes use of the properties of the modified circle polynomials, related to Zernike functions, and of integration in the complex plane of the radial spectral coordinate. The resulting formulation can be estimated extremely fast and is shown to exhibit several expected properties. An asymptotic expression is proposed and validated.},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {64},
number = {1},
pages = {336-339},
issn = {1558-2221},
doi = {10.1109/TAP.2015.2500914},
year = {2017},
url = {http://hdl.handle.net/2078.1/183213}}``````

• G. Hislop, C. Craeye, and D. Gonzalez Ovejero, “Antenna calibration for near-field material characterization,” IEEE Transactions on Antennas and Propagation, vol. 64, pp. 1364-1372, 2016. doi:10.1109/TAP.2016.2526087

A novel antenna calibration method is presented for near-field problems, such as material characterization or inverse scattering. The procedure accurately accounts for differences between simulations of objects close to antennas and the equivalent experimental measurements. It is based on the method of moments (MoM) solution to surface integral scattering equations. An efficient choice of macrobasis functions (MBFs) is applied to the antenna, which reduces the computational costs by several orders of magnitude. The calibration involves scanning a target of known constitution through the antenna near field, assigning a tuning parameter to each MBF and optimizing said parameters, so as to reduce the error between antenna simulations and measurements. This adjusts the antenna’s simulated surface currents, so as to more accurately represent the currents on the experimental apparatus. Thus, an efficient antenna model is obtained, which more accurately represents the real-world antenna. The calibration technique is verified by applying it to the characterization of dielectric objects of known but arbitrary shape.

``````@article{boreal:194967,
title = {Antenna calibration for near-field material characterization},
author = {Hislop, Gregory and Craeye, Christophe and Gonzalez Ovejero, David},
abstract = {A novel antenna calibration method is presented for near-field problems, such as material characterization or inverse scattering. The procedure accurately accounts for differences between simulations of objects close to antennas and the equivalent experimental measurements. It is based on the method of moments (MoM) solution to surface integral scattering equations. An efficient choice of macrobasis functions (MBFs) is applied to the antenna, which reduces the computational costs by several orders of magnitude. The calibration involves scanning a target of known constitution through the antenna near field, assigning a tuning parameter to each MBF and optimizing said parameters, so as to reduce the error between antenna simulations and measurements. This adjusts the antenna’s simulated surface currents, so as to more accurately represent the currents on the experimental apparatus. Thus, an efficient antenna model is obtained, which more accurately represents the real-world antenna. The calibration technique is verified by applying it to the characterization of dielectric objects of known but arbitrary shape.},
Keywords = {Calibration , computational electromagnetic , dielectric constant , electromagnetic tomography , electromagnetics , inverse problems , materials’ testing , microwave measurements , microwave sensors , near fields , near-field radiation pattern , numerical simulation , permittivity measurement},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {64},
pages = {1364-1372},
issn = {1558-2221},
doi = {10.1109/TAP.2016.2526087},
publisher = {I E E E},
year = {2016},
url = {http://hdl.handle.net/2078.1/194967}}``````

• D. Tihon, S. Withington, C. N. Thomas, and C. Craeye, “Characterization of power absorption response of periodic three-dimensional structures to partially coherent fields,” OpticalSocietyofAmerica.JournalA:Optics,ImageScience,andVision, vol. 33, iss. 12, pp. 2459-2469, 2016. doi:10.1364/JOSAA.33.002459

In many applications of absorbing structures it is important to understand their spatial response to incident fields, for example in thermal solar panels, bolometric imaging, and controlling radiative heat transfer. In practice, the illuminating field often originates from thermal sources and is only partially spatially coherent when it reaches the absorbing device. In this paper, we present a method to fully characterize the way a structure can absorb such partially coherent fields. The method is presented for any three-dimensional material and accounts for the partial coherence and partial polarization of the incident light. This characterization can be achieved numerically using simulation results or experimentally using the energy absorption interferometry that has been described previously in the literature. The absorbing structure is characterized through a set of absorbing functions onto which any partially coherent field can be projected. This set is compact for any structure of finite extent, and the absorbing function is discrete for periodic structures.

``````@article{boreal:178724,
title = {Characterization of power absorption response of periodic three-dimensional structures to partially coherent fields},
author = {Tihon, Denis and Withington, Stafford and Thomas, Christopher N. and Craeye, Christophe},
abstract = {In many applications of absorbing structures it is important to understand their spatial response to incident fields, for example in thermal solar panels, bolometric imaging, and controlling radiative heat transfer. In practice, the illuminating field often originates from thermal sources and is only partially spatially coherent when it reaches the absorbing device. In this paper, we present a method to fully characterize the way a structure can absorb such partially coherent fields. The method is presented for any three-dimensional material and accounts for the partial coherence and partial polarization of the incident light. This characterization can be achieved numerically using simulation results or experimentally using the energy absorption interferometry that has been described previously in the literature. The absorbing structure is characterized through a set of absorbing functions onto which any partially coherent field can be projected. This set is compact for any structure of finite extent, and the absorbing function is discrete for periodic structures.},
Keywords = {CISM:CECI},
language = {Anglais},
journal = {OpticalSocietyofAmerica.JournalA:Optics,ImageScience,andVision},
volume = {33},
number = {12},
pages = {2459-2469},
issn = {1520-8532},
doi = {10.1364/JOSAA.33.002459},
publisher = {Optical Society of America},
year = {2016},
url = {http://hdl.handle.net/2078.1/178724}}``````

• Iupikov, C. Craeye, and R. Maaskant, “Domain-decomposition approach to Krylov-subspace iteration,” IEEE Antennas and Wireless Propagation Letters, vol. 15, pp. 1414-1417, 2016. doi:10.1109/LAWP.2015.2511195

Krylov subspace iterative techniques consist of finding the solution of a scattering problem as a linear combination of “generating vectors” obtained through successive matrix-vector multiplications. This paper extends this approach to domaindecomposition. Here, on each subdomain a subspace is obtained by constructing the segments of each generating vector associated with the subdomain, and by weighting these segments independently, which provides more degrees of freedom. The method is tested for scattering by a sphere and a rectangular plate, as well as radiation from connected arrays with strongly coupled antenna elements. It is shown that substantial computational savings can be obtained for the sphere and the array. This opens up new perspectives for faster solutions of multi-scaled problems.

``````@article{boreal:194966,
title = {Domain-decomposition approach to Krylov-subspace iteration},
author = {Iupikov and Craeye, Christophe and Maaskant, Rob},
abstract = {Krylov subspace iterative techniques consist of finding the solution of a scattering problem as a linear combination of “generating vectors” obtained through successive matrix-vector multiplications. This paper extends this approach to domaindecomposition. Here, on each subdomain a subspace is obtained by constructing the segments of each generating vector associated with the subdomain, and by weighting these segments independently, which provides more degrees of freedom. The method is tested for scattering by a sphere and a rectangular plate, as well as radiation from connected arrays with strongly coupled antenna elements. It is shown that substantial computational savings can be obtained for the sphere and the array. This opens up new perspectives for faster solutions of multi-scaled problems.},
Keywords = {domain-decomposition , CBFM , GMRES , Krylov subspace iteration , connected arrays},
language = {Anglais},
journal = {IEEE Antennas and Wireless Propagation Letters},
volume = {15},
pages = {1414-1417},
issn = {1548-5757},
doi = {10.1109/LAWP.2015.2511195},
publisher = {I E E E},
year = {2016},
url = {http://hdl.handle.net/2078.1/194966}}``````

• K. Alkhalifeh, G. Hislop, N. A. Ozdemir, and C. Craeye, “Efficient MoM Simulation of 3D Antennas in the Vicinity of the Ground,” Efficient MoM Simulation of 3D Antennas in the Vicinity of the Ground, vol. 64, iss. 12, 2016. doi:10.1109/TAP.2016.2618482

A novel fast technique is presented to account for the effect of an arbitrary soil permittivity in the analysis of Ground Penetrating Radar (GPR) antennas in the presence of a flat layered ground.We named the method Fast Ground Coupling Matrix (FGCM) because it is expressed as an additional Methodof- Moment impedance matrix obtained from the radiation patterns of the basis/testing functions and the ground reflection coefficient. The advantage of this method is the independence of radiation patterns from the ground’s physical and electromagnetic parameters (layer thickness, complex permittivity, permeability, etc.). The new matrix formulation efficiently calculates the impedance matrix due to the ground’s contribution, with a loop over the ground parameters (permittivity, conductivity and/or permeability), and changing the distance between antenna and ground. The number of samples in (complex) spectral domain is dramatically reduced by explicitly compensating truncation with aliasing errors in the spectral integration. To demonstrate the accuracy and efficiency of the proposed method, numerical results for 3D metallic Vivaldi and typical dipole antennas are presented. A good agreement among the exact Method of Moments (MoM)solutions, the simulation results, and measured data is observed over an ultra-wide bandwidth.

``````@article{boreal:179197,
title = {Efficient MoM Simulation of 3D Antennas in the Vicinity of the Ground},
author = {Alkhalifeh, Khaldoun and Greg Hislop and Nilufer A. Ozdemir and Craeye, Christophe},
abstract = {A novel fast technique is presented to account for the effect of an arbitrary soil permittivity in the analysis of Ground Penetrating Radar (GPR) antennas in the presence of a flat layered ground.We named the method Fast Ground Coupling Matrix (FGCM) because it is expressed as an additional Methodof- Moment impedance matrix obtained from the radiation patterns of the basis/testing functions and the ground reflection coefficient. The advantage of this method is the independence of radiation patterns from the ground’s physical and electromagnetic parameters (layer thickness, complex permittivity, permeability, etc.). The new matrix formulation efficiently calculates the impedance matrix due to the ground’s contribution, with a loop over the ground parameters (permittivity, conductivity and/or permeability), and changing the distance between antenna and ground. The number of samples in (complex) spectral domain is dramatically reduced by explicitly compensating truncation with aliasing errors in the spectral integration. To demonstrate the accuracy and efficiency of the proposed method, numerical results for 3D metallic Vivaldi and typical dipole antennas are presented. A good agreement among the exact Method of Moments (MoM)solutions, the simulation results, and measured data is observed over an ultra-wide bandwidth.},
Keywords = {Ground Penetration Radar (GPR) , Method of Moments , dielectric measurements , permittivity , conductivity , ultra-wide band (UWB) , contour deformation , Green’s function},
language = {Anglais},
journal = {Efficient MoM Simulation of 3D Antennas in the Vicinity of the Ground},
volume = {64},
number = {12},
issn = {1558-2221},
doi = {10.1109/TAP.2016.2618482},
year = {2016},
url = {http://hdl.handle.net/2078.1/179197}}``````

• B. V. Ha, C. Craeye, and S. N. Jha, “Fast Full-Wave Synthesis of Printed Antenna Arrays Including Mutual Coupling,” IEEE Transactions on Antennas and Propagation, vol. 64, iss. 12, pp. 5163-5171, 2016. doi:10.1109/TAP.2016.2617778

A fast full-wave scheme is presented for the analysis of large printed antenna arrays, making use of the macrobasis functions (MBFs) technique. The interaction between MBFs is computed efficiently through a combination of the contour-fast Fourier transform (C-FFT) and interpolatory MBF-based techniques, which effectively deal with different parts of the printed structure. Substantial improvement is introduced to C-FFT by adding up the FFT tables before interpolating, which dramatically reduces the memory required to store the tables and accelerates the method-of-moment matrix filling time. The current on the antenna array and embedded element patterns (EEPs) are then rapidly obtained. Furthermore, an optimization method relying on sequential convex optimization and the fast full-wave scheme is proposed for the array synthesis. At each optimization iteration, EEPs are precomputed and assumed to be locally constant, which enables the implementation of convex programming to rapidly optimize the antenna positions. The EEPs are then quickly updated for the new antenna positions. The scheme enables the efficient inclusion of mutual coupling in array synthesis problems. Numerical results are presented and discussed for the synthesis of linear and planar arrays made of printed bowtie antennas.

``````@article{boreal:181534,
title = {Fast Full-Wave Synthesis of Printed Antenna Arrays Including Mutual Coupling},
author = {Bui Van Ha and Craeye, Christophe and Jha, Shambhu Nath},
abstract = {A fast full-wave scheme is presented for the analysis of large printed antenna arrays, making use of the macrobasis functions (MBFs) technique. The interaction between MBFs is computed efficiently through a combination of the contour-fast Fourier transform (C-FFT) and interpolatory MBF-based techniques, which effectively deal with different parts of the printed structure. Substantial improvement is introduced to C-FFT by adding up the FFT tables before interpolating, which dramatically reduces the memory required to store the tables and accelerates the method-of-moment matrix filling time. The current on the antenna array and embedded element patterns (EEPs) are then rapidly obtained. Furthermore, an optimization method relying on sequential convex optimization and the fast full-wave scheme is proposed for the array synthesis. At each optimization iteration, EEPs are precomputed and assumed to be locally constant, which enables the implementation of convex programming to rapidly optimize the antenna positions. The EEPs are then quickly updated for the new antenna positions. The scheme enables the efficient inclusion of mutual coupling in array synthesis problems. Numerical results are presented and discussed for the synthesis of linear and planar arrays made of printed bowtie antennas.},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {64},
number = {12},
pages = {5163 - 5171},
issn = {1558-2221},
doi = {10.1109/TAP.2016.2617778},
publisher = {I E E E},
year = {2016},
url = {http://hdl.handle.net/2078.1/181534}}``````

• D. Tihon, V. Sozio, N. A. Ozdemir, M. Albani, and C. Craeye, “Numerically Stable Eigenmode Extraction in 3-D Periodic Metamaterials,” IEEE Transactions on Antennas and Propagation, vol. 64, iss. 7, pp. 3068-3079, 2016. doi:10.1109/TAP.2016.2562659

A numerical method is presented to compute the eigenmodes supported by 3-D metamaterials using the method of moments. The method relies on interstitial equivalent currents between layers. First, a parabolic formulation is presented. Then, we present an iterative technique that can be used to linearize the problem. In this way, all the eigenmodes characterized by their transmission coefficients and equivalent interstitial currents can be found using a simple eigenvalue decomposition of a matrix. The accuracy that can be achieved is limited only by the quality of simulation, and we demonstrate that the error introduced when linearizing the problem decreases doubly exponentially with respect to the time devoted to the iterative process. We also draw a mathematical link and distinguish the proposed method from other transfer-matrix-based methods available in the literature.

``````@article{boreal:178744,
title = {Numerically Stable Eigenmode Extraction in 3-D Periodic Metamaterials},
author = {Tihon, Denis and Sozio, Valentina and Ozdemir, Nilufer Aslihan and Albani, Matteo and Craeye, Christophe},
abstract = {A numerical method is presented to compute the eigenmodes supported by 3-D metamaterials using the method of moments. The method relies on interstitial equivalent currents between layers. First, a parabolic formulation is presented. Then, we present an iterative technique that can be used to linearize the problem. In this way, all the eigenmodes characterized by their transmission coefficients and equivalent interstitial currents can be found using a simple eigenvalue decomposition of a matrix. The accuracy that can be achieved is limited only by the quality of simulation, and we demonstrate that the error introduced when linearizing the problem decreases doubly exponentially with respect to the time devoted to the iterative process. We also draw a mathematical link and distinguish the proposed method from other transfer-matrix-based methods available in the literature.},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {64},
number = {7},
pages = {3068-3079},
issn = {1558-2221},
doi = {10.1109/TAP.2016.2562659},
publisher = {I E E E},
year = {2016},
url = {http://hdl.handle.net/2078.1/178744}}``````

• C. Craeye, “On the transmittance between OAM antennas,” IEEE Transactions on Antennas and Propagation, vol. 64, pp. 336-339, 2016. doi:10.1109/TAP.2015.2500914

A quasi-analytical solution is derived for the transmittance between twoOAMantennas. Itmakes useofthe properties of themodiﬁed circle polynomials, related to Zernike functions, and of integration in the complex plane of the radial spectral coordinate. The resulting formulation can be estimated extremely fast and is shown to exhibit several expected properties. An asymptotic expression is proposed and validated.

``````@article{boreal:194968,
title = {On the transmittance between OAM antennas},
author = {Craeye, Christophe},
abstract = {A quasi-analytical solution is derived for the transmittance between twoOAMantennas. Itmakes useofthe properties of themodiﬁed circle polynomials, related to Zernike functions, and of integration in the complex plane of the radial spectral coordinate. The resulting formulation can be estimated extremely fast and is shown to exhibit several expected properties. An asymptotic expression is proposed and validated.},
Keywords = {Aperture antennas , multiplexing , spectral domain analysis},
language = {Anglais},
journal = {IEEE Transactions on Antennas and Propagation},
volume = {64},
pages = {336-339},
issn = {1558-2221},
doi = {10.1109/TAP.2015.2500914},
publisher = {I E E E},
year = {2016},
url = {http://hdl.handle.net/2078.1/194968}}``````

## Conference

201820172016
• S. Hubert, M. Bodehou, and C. Craeye, “Fast spectral iterative tech- nique for the analysis of planarmetasurface-type structures.” 2018.

A fast iterative algorithm based on the Krylov subspace is proposed to simulate the current distribution on large Synthetic Functions eXpansion method (SFX) [10] to solve printed structures. The acceleration is obtained by computing the problem iteratively, while constructing appropriate MBFs. the matrix-vector product series appearing in the formulation The authors of [11] propose a class of basis functions deﬁned in the spectral domain and by making efﬁciently use of the on elliptical patches, which take into account the rotation and Contour-FFT transformation. The resulting algorithm is then very robust, i.e. can be used for any kind of printed structures. the axial ratio of the ellipses. The closed form spectrum of The numerical analysis of modulated metasurface antennas based these basis functions allows an efﬁcient formulation of the on the proposed method is presented and compared with a pre- Method-of-Moments (MoM). validated algorithm, making use of the concept of equivalent However, all these methods cannot be used when no sym- “Impedance Boundary Condition” to directly get the current metries exist at the level of the printed patches or between distribution.

``````@inproceedings{boreal:195110,
title = {Fast spectral iterative tech- nique for the analysis of planarmetasurface-type structures},
author = {Hubert, Simon and Bodehou, Modeste and Craeye, Christophe},
abstract = {A fast iterative algorithm based on the Krylov subspace is proposed to simulate the current distribution on large Synthetic Functions eXpansion method (SFX) [10] to solve printed structures. The acceleration is obtained by computing the problem iteratively, while constructing appropriate MBFs. the matrix-vector product series appearing in the formulation The authors of [11] propose a class of basis functions deﬁned in the spectral domain and by making efﬁciently use of the on elliptical patches, which take into account the rotation and Contour-FFT transformation. The resulting algorithm is then very robust, i.e. can be used for any kind of printed structures. the axial ratio of the ellipses. The closed form spectrum of The numerical analysis of modulated metasurface antennas based these basis functions allows an efﬁcient formulation of the on the proposed method is presented and compared with a pre- Method-of-Moments (MoM). validated algorithm, making use of the concept of equivalent However, all these methods cannot be used when no sym- “Impedance Boundary Condition” to directly get the current metries exist at the level of the printed patches or between distribution.},
Keywords = {method-of-moments (MoM) , spectral domain methods , metasurfaces , fast numerical method , contour-FFT},
language = {Anglais},
year = {2018},
url = {http://hdl.handle.net/2078.1/195110}}``````

• J. Léger, T. Pairon, and C. Craeye, “Analytical Formulation for the micro-Doppler Spectrum for Rotating Targets in the Near-Field,” in Proceedings of the 11th European Conference on Antennas and Propagation – EUCAP 2017, 2017. doi:10.23919/EuCAP.2017.7928495

The analysis of the Doppler signal returned by rotating targets is of great interest in the framework of target recognition and equipment monitoring. An analytical expression of such a signal already exists for the far-field case, based on the Jacobi-Anger expansion. An extension of this analytical expression is proposed for the near-field case. The solution involves a closed-form expression of each harmonic complex coefficient. An error analysis is carried out.

``````@inproceedings{boreal:195155,
title = {Analytical Formulation for the micro-Doppler Spectrum for Rotating Targets in the Near-Field},
author = {Léger, Jean and Pairon, Thomas and Craeye, Christophe},
abstract = {The analysis of the Doppler signal returned by rotating targets is of great interest in the framework of target recognition and equipment monitoring. An analytical expression of such a signal already exists for the far-field case, based on the Jacobi-Anger expansion. An extension of this analytical expression is proposed for the near-field case. The solution involves a closed-form expression of each harmonic complex coefficient. An error analysis is carried out.},
language = {Anglais},
booktitle = {Proceedings of the 11th European Conference on Antennas and Propagation - EUCAP 2017},
doi = {10.23919/EuCAP.2017.7928495},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195155}}``````

• D. Tihon and C. Craeye, “Closed-form evaluation of the singular terms in electric field integral equations,” in 2017 11th European Conference on Antennas and Propagation (EUCAP), 2017. doi:10.23919/eucap.2017.7928853
``````@inproceedings{boreal:195100,
title = {Closed-form evaluation of the singular terms in electric field integral equations},
author = {Tihon, Denis and Craeye, Christophe},
Keywords = {Method of Moments},
language = {Anglais},
booktitle = {2017 11th European Conference on Antennas and Propagation (EUCAP)},
doi = {10.23919/eucap.2017.7928853},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195100}}``````

• D. Tihon, S. Withington, C. N. Thomas, and C. Craeye, “Computation of the absorption of partially coherent fields using traditional coherent solvers,” in NEMO 2017, 2017. doi:10.1109/nemo.2017.7964276
``````@inproceedings{boreal:195101,
title = {Computation of the absorption of partially coherent fields using traditional coherent solvers},
author = {Tihon, Denis and Withington, Stafford and Thomas, Christopher N. and Craeye, Christophe},
language = {Anglais},
booktitle = {NEMO 2017},
doi = {10.1109/nemo.2017.7964276},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195101}}``````

• B. V. Ha and C. Craeye, “Correlation between SKA1-LOW stations including mutual coupling,” in 2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), 2017. doi:10.1109/iceaa.2017.8065542

Correlation between SKA-LOW stations is studied in this paper. The mutual coupling is taken into account via embedded element patterns obtained from the simulation of the whole stations. To reduce the sidelobes in the correlated pattern, a rotation of stations is implemented. This results in a smoother behavior in the sidelobe region. Moreover, the spherical-wave expansion is exploited to represent station beam pattern, which then facilitates the correlation between stations.

``````@inproceedings{boreal:193631,
title = {Correlation between SKA1-LOW stations including mutual coupling},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {Correlation between SKA-LOW stations is studied in this paper. The mutual coupling is taken into account via embedded element patterns obtained from the simulation of the whole stations. To reduce the sidelobes in the correlated pattern, a rotation of stations is implemented. This results in a smoother behavior in the sidelobe region. Moreover, the spherical-wave expansion is exploited to represent station beam pattern, which then facilitates the correlation between stations.},
language = {Anglais},
booktitle = {2017 International Conference on Electromagnetics in Advanced Applications (ICEAA)},
doi = {10.1109/iceaa.2017.8065542},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/193631}}``````

• B. V. Ha and C. Craeye, “Inclusion of Signal and Noise Coupling in Sparse Wideband Array Synthesis,” , Cambridge, 2017, pp. 1549-1552. doi:10.1109/PIERS.2017.8261993

It is well known that non-regular sparse arrays can strongly reduce the number of active channels while avoiding the appearance of grating lobes [1]. Such configurations avoid “intersecting” effective areas and space tapering can to a certain extent, replace amplitude tapering, with a positive impact on sensitivity. The combination of space tapering and amplitude tapering has been analysed in [2], where the amplitudes compensate for the local variation of the array density. In [3], this has been extended by describing the space tapering through a change of coordinates. In this case, the amplitude tapering is applied before space tapering, i.e. on the initial array, which has as a constant average density. This allows one to limit the amplitude variations imposed on the elements, which is favourable in terms of signal-to-noise ratio, while the main lobes and first few sidelobes have a very smooth behaviour. In the present paper, this work is extended to include mutual coupling between the elements. The work relies on a fast in-house solver, making use of Macro Basis Functions (MBFs) and on a model-based technique for computing the interactions between MBFs without computing the method-of-moments impedance matrix. Regarding the signal analysis, the amplitudes are modulated by the product between the local areas allotted to the element, multiplied by the embedded element pattern. In this work, noise-coupling is also accounted for. Numerical examples will be shown for arrays made of log-periodic antennas, foreseen for the Square Kilometre Array (SKA) telescope. The impact of the proposed combination of amplitude and space tapering on the array sensitivity will be illustrated.

``````@inproceedings{boreal:193605,
title = {Inclusion of Signal and Noise Coupling in Sparse Wideband Array Synthesis},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {It is well known that non-regular sparse arrays can strongly reduce the number of active channels while avoiding the appearance of grating lobes [1]. Such configurations avoid "intersecting" effective areas and space tapering can to a certain extent, replace amplitude tapering, with a positive impact on sensitivity. The combination of space tapering and amplitude tapering has been analysed in [2], where the amplitudes compensate for the local variation of the array density. In [3], this has been extended by describing the space tapering through a change of coordinates. In this case, the amplitude tapering is applied before space tapering, i.e. on the initial array, which has as a constant average density. This allows one to limit the amplitude variations imposed on the elements, which is favourable in terms of signal-to-noise ratio, while the main lobes and first few sidelobes have a very smooth behaviour. In the present paper, this work is extended to include mutual coupling between the elements. The work relies on a fast in-house solver, making use of Macro Basis Functions (MBFs) and on a model-based technique for computing the interactions between MBFs without computing the method-of-moments impedance matrix. Regarding the signal analysis, the amplitudes are modulated by the product between the local areas allotted to the element, multiplied by the embedded element pattern. In this work, noise-coupling is also accounted for. Numerical examples will be shown for arrays made of log-periodic antennas, foreseen for the Square Kilometre Array (SKA) telescope. The impact of the proposed combination of amplitude and space tapering on the array sensitivity will be illustrated.},
language = {Anglais},
journal = {Progress in Electromagnetics Research Symposium},
volume = {1},
pages = {1549-1552},
doi = {10.1109/PIERS.2017.8261993},
year = {2017},
url = {http://hdl.handle.net/2078.1/193605}}``````

• S. Hubert, A. Vallecchi, A. Schuchinsky, and C. Craeye, “Modeling of Impedance-Loaded Sub-Wavelength Metasurfaces.” 2017.

In the context of the optimization of a versatile type of metasurface consisting of inter- twined spirals printed on a dielectric substrate and loaded with discrete impedances, we propose a sim- ple development of the method of moments inter- action matrix that allows obtaining the scattered ﬁeld almost instantly for any distribution of discrete loads. Simulation results for a sample design are presented to illustrate the eﬀectiveness and validity of the method.

``````@inproceedings{boreal:195109,
title = {Modeling of Impedance-Loaded Sub-Wavelength Metasurfaces},
author = {Hubert, Simon and Andrea Vallecchi and Alex Schuchinsky and Craeye, Christophe},
abstract = {In the context of the optimization of a versatile type of metasurface consisting of inter- twined spirals printed on a dielectric substrate and loaded with discrete impedances, we propose a sim- ple development of the method of moments inter- action matrix that allows obtaining the scattered ﬁeld almost instantly for any distribution of discrete loads. Simulation results for a sample design are presented to illustrate the eﬀectiveness and validity of the method.},
Keywords = {metasurface , numerical mathod , load , reflectarray},
language = {Anglais},
year = {2017},
url = {http://hdl.handle.net/2078.1/195109}}``````

• B. V. Ha and C. Craeye, “Numerical Modelling of SKA AA-Mid Tile Configurations Using HARP,” in European conference on Antennas and Propagations, 2017, pp. 3837-3841. doi:10.23919/EuCAP.2017.7928253

The Square Kilometre Array – Aperture Array Midfrequency instrument will be part of the largest next generation radio telescope. To meet the scientific requirements while maintaining a lower number of antenna elements, the University of Cambridge is developing a sparse random array solution using log-periodic dipole array antennas. In this paper we present the application of HARP, a numerical method based on the Method of Moments capable of simulating very large finite arrays of disconnected antennas, to analyze different sub-array configurations based on 16-element tiles and compare it to a randomized 64 element array.

``````@inproceedings{boreal:193615,
title = {Numerical Modelling of SKA AA-Mid Tile Configurations Using HARP},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {The Square Kilometre Array - Aperture Array Midfrequency instrument will be part of the largest next generation radio telescope. To meet the scientific requirements while maintaining a lower number of antenna elements, the University of Cambridge is developing a sparse random array solution using log-periodic dipole array antennas. In this paper we present the application of HARP, a numerical method based on the Method of Moments capable of simulating very large finite arrays of disconnected antennas, to analyze different sub-array configurations based on 16-element tiles and compare it to a randomized 64 element array.},
language = {Anglais},
booktitle = {European conference on Antennas and Propagations},
journal = {European Conference on Antennas and Propagation (EUCAP), 2017},
volume = {1},
pages = {3837-3841},
doi = {10.23919/EuCAP.2017.7928253},
year = {2017},
url = {http://hdl.handle.net/2078.1/193615}}``````

• M. Bodehou, D. Gonzales-Ovejero, C. Craeye, and I. Huynen, “Numerical analysis of modulated metasurface antennas using Fourier-Bessel basis functions,” in Proceedings of the IEEE Conference on Numerical, Electromagnetic multiphysics and optimization, for RF, microwave and terahertz, USA, 2017. doi:10.1109/NEMO.2017.7964219

Metasurfaces are thin (2D) metamaterials designed for manipulating the dispersion properties of surface-waves (SWs) or the reflection properties of incident plane-waves. Thanks to the sub-wavelength sizes of the patches used in the implementation step, these surfaces can be described by a surface impedance boundary condition (IBC). In this paper, we investigate a ‘Method of Moments’ (MoM) based analysis of such surface with a family of entire-domain basis functions named ‘Fourier-Bessel’ functions. The orthogonality property of these functions on a disk allows us to represent any smooth current distribution in an effective manner and thereby to drastically reduce the size of the MoM matrix.

``````@inproceedings{boreal:190067,
title = {Numerical analysis of modulated metasurface antennas using Fourier-Bessel basis functions},
author = {Bodehou, Modeste and Gonzales-Ovejero, D. and Craeye, Christophe and Huynen, Isabelle},
abstract = {Metasurfaces are thin (2D) metamaterials designed for manipulating the dispersion properties of surface-waves (SWs) or the reflection properties of incident plane-waves. Thanks to the sub-wavelength sizes of the patches used in the implementation step, these surfaces can be described by a surface impedance boundary condition (IBC). In this paper, we investigate a 'Method of Moments' (MoM) based analysis of such surface with a family of entire-domain basis functions named 'Fourier-Bessel' functions. The orthogonality property of these functions on a disk allows us to represent any smooth current distribution in an effective manner and thereby to drastically reduce the size of the MoM matrix.},
Keywords = {Surface impedance , Current distribution , Impedance , Surface waves , Microwave antennas , Method of moments},
language = {Anglais},
booktitle = {Proceedings of the IEEE Conference on Numerical, Electromagnetic multiphysics and optimization, for RF, microwave and terahertz},
doi = {10.1109/NEMO.2017.7964219},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/190067}}``````

• H. A. Kayani, K. Alkhalifeh, and C. Craeye, “Open-Circuit to Embedded Pattern Approach with Harmonic Optimization in ESPAR,” in Proceedings of the International Conference NEMO 2017, 2017. doi:10.1109/NEMO.2017.7964177

``````@inproceedings{boreal:195137,
title = {Open-Circuit to Embedded Pattern Approach with Harmonic Optimization in ESPAR},
author = {Kayani, Husnain Ali and Alkhalifeh, Khaldoun and Craeye, Christophe},
Keywords = {Antenna radiation patterns ,    Antenna arrays ,    Optimization ,    Load modeling ,    Loaded antennas ,    Harmonic analysis ,    Dipole antennas},
language = {Anglais},
booktitle = {Proceedings of the International Conference NEMO 2017},
doi = {10.1109/NEMO.2017.7964177},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195137}}``````

• J. I. Echeveste Guzman and C. Craeye, “Optimization of the array element positions based on the analytical dependence of the mutual coupling in the GSM array formulation,” in Proceedings of the International Conference NEMO 2017, 2017. doi:10.1109/NEMO.2017.7964248

Positions of array antenna elements are optimized taking advantage of the analytical dependence of the mutual coupling in the Generalized Scattering Matrix (GSM) finite array formulation. First, spatial derivatives for the GSM formulation are analytically computed. Then, they are applied to the synthesis of uniform amplitude finite arrays, by rotating the elements of the array or by changing their positions, through a gradientbased optimization method.

``````@inproceedings{boreal:195138,
title = {Optimization of the array element positions based on the analytical dependence of the mutual coupling in the GSM array formulation},
author = {Echeveste Guzman, Jose Ignacio and Craeye, Christophe},
abstract = {Positions of array antenna elements are optimized taking advantage of the analytical dependence of the mutual coupling in the Generalized Scattering Matrix (GSM) finite array formulation. First, spatial derivatives for the GSM formulation are analytically computed. Then, they are applied to the synthesis of uniform amplitude finite arrays, by rotating the elements of the array or by changing their positions, through a gradientbased optimization method.},
Keywords = {finite array synthesis; mutual coupling; generalized scattering matrix; gradient-based optimization},
language = {Anglais},
booktitle = {Proceedings of the International Conference NEMO 2017},
doi = {10.1109/NEMO.2017.7964248},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195138}}``````

• S. Karki, J. I. Echeveste Guzman, T. Pairon, and C. Craeye, “Sequentially Shifted Beamforming from a Conformed Conical Array,” in Proceedings of the 47th European Microwave Conference 2017, 2017. doi:10.23919/EURAD.2017.8249223

A conical frustum array capable of beamforming in azimuth is proposed. The design exploits the embedded element pattern of a single facet of the conical frustum array to determine the number of consecutive facets required, and to ascertain the directions at which a handover to the next set of facets is required. A simple beamforming architecture is also presented, which can perform sequential shifting of facets with a minimal number of analog switches and 15 true-time delay lines to produce 36 beams. Such conical frustum array can easily communicate with or track objects beneath when attached to flying platforms.

``````@inproceedings{boreal:195151,
title = {Sequentially Shifted Beamforming from a Conformed Conical Array},
author = {Karki, Sumit and Echeveste Guzman, Jose Ignacio and Pairon, Thomas and Craeye, Christophe},
abstract = {A conical frustum array capable of beamforming in azimuth is proposed. The design exploits the embedded element pattern of a single facet of the conical frustum array to determine the number of consecutive facets required, and to ascertain the directions at which a handover to the next set of facets is required. A simple beamforming architecture is also presented, which can perform sequential shifting of facets with a minimal number of analog switches and 15 true-time delay lines to produce 36 beams. Such conical frustum array can easily communicate with or track objects beneath when attached to flying platforms.},
Keywords = {Array signal processing ,    Azimuth ,    Directive antennas ,    Radio frequency ,    Phased arrays},
language = {Anglais},
booktitle = {Proceedings of the 47th European Microwave Conference 2017},
publisher = {IEEE},
year = {2017},
url = {http://hdl.handle.net/2078.1/195151}}``````

• S. Karki, C. Craeye, M. Mitrovic, and V. Dehant, “A conical frustum-type array devoted to a Mars-based transponder,” in Proceedings of the 2016 10th European Conference on Antennas and Propagation (EuCAP), 2016. doi:10.1109/EuCAP.2016.7481529

A crossed slot circularly polarized antenna array conforming to a conical frustum is proposed for a Mars transponder. The cross-slot antenna element is aperture-coupled by a single stripline feed, and its properties are studied. Also, the entire slot antenna array fed with discrete delta-gap sources to produce circular polarization is also described. Eventually, the slot array would all be replaced by stripline feeds with phase control to perform analog beamforming.

``````@inproceedings{boreal:182090,
title = {A conical frustum-type array devoted to a Mars-based transponder},
author = {Karki, Sumit and Craeye, Christophe and Mitrovic, Michel and Dehant, Veronique},
abstract = {A crossed slot circularly polarized antenna array conforming to a conical frustum is proposed for a Mars transponder. The cross-slot antenna element is aperture-coupled by a single stripline feed, and its properties are studied. Also, the entire slot antenna array fed with discrete delta-gap sources to produce circular polarization is also described. Eventually, the slot array would all be replaced by stripline feeds with phase control to perform analog beamforming.},
language = {Anglais},
booktitle = {Proceedings of the 2016 10th European Conference on Antennas and Propagation (EuCAP)},
doi = {10.1109/EuCAP.2016.7481529},
year = {2016},
url = {http://hdl.handle.net/2078.1/182090}}``````

• C. Craeye, “A series representation for the intermediate-field transmittance between apertures,” in Proceedings of the 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016, 2016. doi:10.1109/URSI-EMTS.2016.7571363

A recent communication provided a model for the transmittance between two antennas supporting Orbital Angular Momentum modes. That formulation involved a single integral along the radial spectral coordinate. That approach actually also applies to any pair of apertures supporting arbitrary distributions. Asymptotically, for far field conditions, an analytical expression has been developed, as a power of the near-field parameter, corresponding to the ratio between the far-field limit and the distance between antennas. This expansion is extended to the intermediate-field region, as a polynomial of the near-field parameter. The convergence of this method is discussed, along with the corresponding time savings and limitations.

``````@inproceedings{boreal:195122,
title = {A series representation for the intermediate-field transmittance between apertures},
author = {Craeye, Christophe},
abstract = {A recent communication provided a model for the transmittance between two antennas supporting Orbital Angular Momentum modes. That formulation involved a single integral along the radial spectral coordinate. That approach actually also applies to any pair of apertures supporting arbitrary distributions. Asymptotically, for far field conditions, an analytical expression has been developed, as a power of the near-field parameter, corresponding to the ratio between the far-field limit and the distance between antennas. This expansion is extended to the intermediate-field region, as a polynomial of the near-field parameter. The convergence of this method is discussed, along with the corresponding time savings and limitations.},
Keywords = {Antennas , Apertures , Transmitting antennas , Current distribution , Convergence , Acceleration , Receiving antennas},
language = {Anglais},
booktitle = {Proceedings of the 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016},
doi = {10.1109/URSI-EMTS.2016.7571363},
publisher = {IEEE},
year = {2016},
url = {http://hdl.handle.net/2078.1/195122}}``````

• C. Craeye and B. V. Ha, “Density tapering for antenna arrays based on a coordinate transform,” in Electromagnetic Theory (EMTS), 2016 URSI International Symposium on, 2016. doi:10.1109/URSI-EMTS.2016.7571493

A differential equation is established to transform an array with constant average density into an array with prescribed density. It is shown that this allows good control over the first few sidelobes. This is especially true when combined with a limited amplitude weighting that compensates for local density variations, with limited effect on the array sensitivity.

``````@inproceedings{boreal:181525,
title = {Density tapering for antenna arrays based on a coordinate transform},
author = {Craeye, Christophe and Bui Van Ha},
abstract = {A differential equation is established to transform an array with constant average density into an array with prescribed density. It is shown that this allows good control over the first few sidelobes. This is especially true when combined with a limited amplitude weighting that compensates for local density variations, with limited effect on the array sensitivity.},
language = {Anglais},
booktitle = {Electromagnetic Theory (EMTS), 2016 URSI International Symposium on},
doi = {10.1109/URSI-EMTS.2016.7571493},
year = {2016},
url = {http://hdl.handle.net/2078.1/181525}}``````

• C. Craeye, B. Douglas, N. Razavi, and B. V. Ha, “Density tapering for antenna arrays based on a coordinate transform,” in Proceedings of the 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016, 2016. doi:10.1109/URSI-EMTS.2016.7571493

A differential equation is established to transform an array with constant average density into an array with prescribed density. It is shown that this allows good control over the first few sidelobes. This is especially true when combined with a limited amplitude weighting that compensates for local density variations, with limited effect on the array sensitivity.

``````@inproceedings{boreal:195120,
title = {Density tapering for antenna arrays based on a coordinate transform},
author = {Craeye, Christophe and Buisson Douglas and Razavi, Nima and Bui Van Ha},
abstract = {A differential equation is established to transform an array with constant average density into an array with prescribed density. It is shown that this allows good control over the first few sidelobes. This is especially true when combined with a limited amplitude weighting that compensates for local density variations, with limited effect on the array sensitivity.},
language = {Anglais},
booktitle = {Proceedings of the 2016 URSI International Symposium on Electromagnetic Theory, EMTS 2016},
doi = {10.1109/URSI-EMTS.2016.7571493},
publisher = {IEEE},
year = {2016},
url = {http://hdl.handle.net/2078.1/195120}}``````

• T. Pairon, C. Craeye, and C. Oestges, “Doppler Spectrum of a Rotating Smooth Cylinder,” in Proceedings 10th European Conference on Antennas and Propagation (EuCAP), 2016. doi:10.1109/EuCAP.2016.7482004

The Doppler spectrum of a rotating smooth cylinder is investigated both theoretically and experimentally. Since the studied object has a smooth surface and is large compared to the wavelength, the physical optics (PO) approximation is used. The integration of the surface currents is computed with a hybrid method which consists of integrating analytically the currents in one dimension using the stationary phase method (SPM), while the currents in the other dimension are integrated numerically. This enables a reduction of the computation time compared to a fully numerical integration. Simulations are compared with measurements.

``````@inproceedings{boreal:179924,
title = {Doppler Spectrum of a Rotating Smooth Cylinder},
author = {Pairon, Thomas and Craeye, Christophe and Oestges, Claude},
abstract = {The Doppler spectrum of a rotating smooth cylinder is investigated both theoretically and experimentally. Since the studied object has a smooth surface and is large compared to the wavelength, the physical optics (PO) approximation is used. The integration of the surface currents is computed with a hybrid method which consists of integrating analytically the currents in one dimension using the stationary phase method (SPM), while the currents in the other dimension are integrated numerically. This enables a reduction of the computation time compared to a fully numerical integration. Simulations are compared with measurements.},
Keywords = {ICTEAM:COMM},
language = {Anglais},
booktitle = {Proceedings 10th European Conference on Antennas and Propagation (EuCAP)},
doi = {10.1109/EuCAP.2016.7482004},
year = {2016},
url = {http://hdl.handle.net/2078.1/179924}}``````

• B. V. Ha and C. Craeye, “Efficient array synthesis of printed arrays including mutual coupling,” in Proceeding of EuCAP on IEEE, 2016. doi:10.1109/EuCAP.2016.7481491

An efficient approach for array synthesis including the effect of mutual coupling is presented. The method is based on an iterative convex optimization scheme and on a fast full-wave simulation technique. The embedded element patterns (EEP), obtained by full-wave simulation at each iteration of the convex optimization, are exploited to take into account the mutual coupling. The final results, therefore, not only satisfy the pre-defined constraints but also guarantee the performance of the array. Numerical results of linear focused beam arrays are presented to show the effectiveness of the approach.

``````@inproceedings{boreal:181520,
title = {Efficient array synthesis of printed arrays including mutual coupling},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {An efficient approach for array synthesis including the effect of mutual coupling is presented. The method is based on an iterative convex optimization scheme and on a fast full-wave simulation technique. The embedded element patterns (EEP), obtained by full-wave simulation at each iteration of the convex optimization, are exploited to take into account the mutual coupling. The final results, therefore, not only satisfy the pre-defined constraints but also guarantee the performance of the array. Numerical results of linear focused beam arrays are presented to show the effectiveness of the approach.},
language = {Anglais},
booktitle = {Proceeding of EuCAP on IEEE},
doi = {10.1109/EuCAP.2016.7481491},
year = {2016},
url = {http://hdl.handle.net/2078.1/181520}}``````

• Q. Gueuning, S. Hubert, C. Craeye, and C. Oestges, “Error model for Contour-FFT evaluation of the free-space on-plane Green’s function,” in Proceedings 2016 URSI International Symposium on Electromagnetic Theory (EMTS), 2016. doi:10.1109/URSI-EMTS.2016.7571383 10.1109/URSI-EMTS.2016.7571383

Closed-form analytical expressions are derived for the numerical integration of the spectral Green’s function with Contour-FFT. Results indicates that a proper uniform grid of spatial points enhances the convergence rate of the truncation error, that the Nyquist-Shannon theorem can be generalized to inverse Laplace transforms on linear path and that the relative error specific to Contour-FFT is a regularized gamma function. Two examples illustrate the modularity of the approach.

``````@inproceedings{boreal:179922,
title = {Error model for Contour-FFT evaluation of the free-space on-plane Green's function},
author = {Gueuning, Quentin and Hubert, Simon and Craeye, Christophe and Oestges, Claude},
abstract = {Closed-form analytical expressions are derived for the numerical integration of the spectral Green's function with Contour-FFT. Results indicates that a proper uniform grid of spatial points enhances the convergence rate of the truncation error, that the Nyquist-Shannon theorem can be generalized to inverse Laplace transforms on linear path and that the relative error specific to Contour-FFT is a regularized gamma function. Two examples illustrate the modularity of the approach.},
Keywords = {ICTEAM:COMM},
language = {Anglais},
booktitle = {Proceedings 2016 URSI International Symposium on Electromagnetic Theory (EMTS)},
doi = {10.1109/URSI-EMTS.2016.7571383 10.1109/URSI-EMTS.2016.7571383},
year = {2016},
url = {http://hdl.handle.net/2078.1/179922}}``````

• B. V. Ha and C. Craeye, “Fast Optimization of Large Antenna Arrays on Dielectric Layers using Surrogate Macro-Basis-Function Representations,” in IEEE Symposium Series on Computational Intelligence (IEEE SSCI 2016), 2016. doi:10.1109/SSCI.2016.7849901

A fast full-wave simulation for the synthesis of printed antenna arrays is presented. The technique relies on a fast simulation scheme, exploiting the Macro Basis Functions (MBF) technique, to quickly analyze arrays. Mutual coupling (MC) is taken into account by exploiting the embedded element patterns in the synthesis process. The technique is hybridized with an iterative convex optimization to effectively optimize antenna excitation and locations in a double-step optimization routine. The synthesized arrays will therefore fulfill all requirements.The performance of the method is validated for arrays of printed bowtie antennas.

``````@inproceedings{boreal:181565,
title = {Fast Optimization of Large Antenna Arrays on Dielectric Layers using Surrogate Macro-Basis-Function Representations},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {A fast full-wave simulation for the synthesis of printed antenna arrays is presented. The technique relies on a fast simulation scheme, exploiting the Macro Basis Functions (MBF) technique, to quickly analyze arrays. Mutual coupling (MC) is taken into account by exploiting the embedded element patterns in the synthesis process. The technique is hybridized with an iterative convex optimization to effectively optimize antenna excitation and locations in a double-step optimization routine. The synthesized arrays will therefore fulfill all requirements.The performance of the method is validated for arrays of printed bowtie antennas.},
language = {Anglais},
booktitle = {IEEE Symposium Series on Computational Intelligence (IEEE SSCI 2016)},
editor = {IEEE},
doi = {10.1109/SSCI.2016.7849901},
year = {2016},
url = {http://hdl.handle.net/2078.1/181565}}``````

• D. Tihon and C. Craeye, “Fast computation of the impedance matrix for the periodic Method of Moments using a plane wave decomposition.” 2016, pp. 1-4. doi:10.1109/EuCAP.2016.7481735

Full-wave simulations of 2D periodic arrays using the Method of Moments (MoM) are investigated. A method based on plane wave decomposition is used to fill the MoM impedance matrix. For pair of basis and testing functions that are close to each other, a singular term is removed before extrapolating the value of the impedance matrix using a Taylor expansion. The two main advantages of this method are the easy computation of the derivative of the impedance matrix involved in the Taylor expansion and the fact that the singularity extraction can be performed once for all phase shifts between consecutive unit cells. The latter property proves to be useful when the Array Scanning Method (ASM) is to be used.

``````@inproceedings{boreal:178722,
title = {Fast computation of the impedance matrix for the periodic Method of Moments using a plane wave decomposition},
author = {Tihon, Denis and Craeye, Christophe},
abstract = {Full-wave simulations of 2D periodic arrays using the Method of Moments (MoM) are investigated. A method based on plane wave decomposition is used to fill the MoM impedance matrix. For pair of basis and testing functions that are close to each other, a singular term is removed before extrapolating the value of the impedance matrix using a Taylor expansion. The two main advantages of this method are the easy computation of the derivative of the impedance matrix involved in the Taylor expansion and the fact that the singularity extraction can be performed once for all phase shifts between consecutive unit cells. The latter property proves to be useful when the Array Scanning Method (ASM) is to be used.},
language = {Anglais},
journal = {Antennas and propagation (EuCAP), 2016 10th European Conference on},
volume = {1},
number = {1},
pages = {1-4},
issn = {0000-0000},
doi = {10.1109/EuCAP.2016.7481735},
year = {2016},
url = {http://hdl.handle.net/2078.1/178722}}``````

• D. Tihon and C. Craeye, “Full-wave simulation of semi-infinite periodic metamaterials.” 2016, pp. 355-357. doi:10.1109/MetaMaterials.2016.7746397

The full-wave simulation of semi-infinite metamaterials is a key tool to the understanding of surface-bounded wave phenomena. In this paper, we present a method that can be used to model a semi-infinite metamaterial using full-wave simulations based on the Method of Moments. First, the impedance matrices describing one layer of the metamaterial are transformed in order to obtain the response of a semi-infinite metamaterial. Then, the fields within the first layers of the structure are computed recursively. The whole process is numerically stable. Numerical results are provided as an illustration.

``````@inproceedings{boreal:178723,
title = {Full-wave simulation of semi-infinite periodic metamaterials},
author = {Tihon, Denis and Craeye, Christophe},
abstract = {The full-wave simulation of semi-infinite metamaterials is a key tool to the understanding of surface-bounded wave phenomena. In this paper, we present a method that can be used to model a semi-infinite metamaterial using full-wave simulations based on the Method of Moments. First, the impedance matrices describing one layer of the metamaterial are transformed in order to obtain the response of a semi-infinite metamaterial. Then, the fields within the first layers of the structure are computed recursively. The whole process is numerically stable. Numerical results are provided as an illustration.},
language = {Anglais},
journal = {Advanced Electromagnetic Materials in Microwaves and Optics (METAMATERIALS), 2016 10th International Congress on},
volume = {1},
number = {1},
pages = {355-357},
issn = {0000-0000},
doi = {10.1109/MetaMaterials.2016.7746397},
year = {2016},
url = {http://hdl.handle.net/2078.1/178723}}``````

• B. V. Ha and C. Craeye, “Further validation of fast simulation method at the element and array pattern levels for SKA,” in Proceeding of EuCAP on IEEE, 2016. doi:10.1109/EuCAP.2016.7481791

This paper present further validations of a Method of Moment (MoM) based technique dedicated to fast simulation of SKA-low arrays. In particular, the embedded element patterns and array patterns are studied. The patterns obtained using this technique are compared with those using the commercial software CST. The comparison shows the importance of the mutual coupling in modeling these patterns. Further validation is demonstrated by an example of nulling in the presence of mutual coupling.

``````@inproceedings{boreal:181519,
title = {Further validation of fast simulation method at the element and array pattern levels for SKA},
author = {Bui Van Ha and Craeye, Christophe},
abstract = {This paper present further validations of a Method of Moment (MoM) based technique dedicated to fast simulation of SKA-low arrays. In particular, the embedded element patterns and array patterns are studied. The patterns obtained using this technique are compared with those using the commercial software CST. The comparison shows the importance of the mutual coupling in modeling these patterns. Further validation is demonstrated by an example of nulling in the presence of mutual coupling.},
language = {Anglais},
booktitle = {Proceeding of EuCAP on IEEE},
doi = {10.1109/EuCAP.2016.7481791},
year = {2016},
url = {http://hdl.handle.net/2078.1/181519}}``````

• S. Hubert, S. N. Jha, and C. Craeye, “Layered green’s functions estimation with Contour-FFT,” in Proceedings 10th European Conference on Antennas and Propagation (EuCAP), 2016.

The Contour-FFT is a recent method based on the Method of Moments which is intended to analyse very large irregular antenna arrays printed on layered substrates. This method relies on some parameters that can be hard to adjust for certain cases: typically thin or high-permittivity substrates. In this work we propose a simple hybrid spectral/spatial domain approach to overcome this problem, and we show that it very efficiently improves the accuracy without altering the attractive time complexity of the Contour-FFT. We also propose to apply the Contour-FFT only to the portion of the spectral domain that contains the contour, leading to important time saving factors.

``````@inproceedings{boreal:188122,
title = {Layered green's functions estimation with Contour-FFT},
author = {Hubert, Simon and Jha, Shambhu Nath and Craeye, Christophe},
abstract = {The Contour-FFT is a recent method based on the Method of Moments which is intended to analyse very large irregular antenna arrays printed on layered substrates. This method relies on some parameters that can be hard to adjust for certain cases: typically thin or high-permittivity substrates. In this work we propose a simple hybrid spectral/spatial domain approach to overcome this problem, and we show that it very efficiently improves the accuracy without altering the attractive time complexity of the Contour-FFT. We also propose to apply the Contour-FFT only to the portion of the spectral domain that contains the contour, leading to important time saving factors.},
Keywords = {Contour-FFT , Green , layered medium , numerical methods},
language = {Anglais},
booktitle = {Proceedings 10th European Conference on Antennas and Propagation (EuCAP)},
year = {2016},
url = {http://hdl.handle.net/2078.1/188122}}``````

• C. Craeye and B. V. Ha, “On the effects of mutual coupling in the active reflection coefficient of wide-field scanning electrically large random phased arrays,” in Proceeding of ICEAA on IEEE, 2016. doi:10.1109/ICEAA.2016.7731490

Wide-angle scanning phased arrays suffer from bandwidth limitations due to the effects of mutual coupling. If the array is regular, blind scan anomalies can be found in the active reflection coefficient in band for even 2:1 bandwidth ratios. If the array has a random distribution of elements however, we can see how the effects of mutual coupling randomize out in the active reflection coefficient, effectively increasing the frequency and scan range bandwidth.

``````@inproceedings{boreal:181533,
title = {On the effects of mutual coupling in the active reflection coefficient of wide-field scanning electrically large random phased arrays},
author = {Craeye, Christophe and Bui Van Ha},
abstract = {Wide-angle scanning phased arrays suffer from bandwidth limitations due to the effects of mutual coupling. If the array is regular, blind scan anomalies can be found in the active reflection coefficient in band for even 2:1 bandwidth ratios. If the array has a random distribution of elements however, we can see how the effects of mutual coupling randomize out in the active reflection coefficient, effectively increasing the frequency and scan range bandwidth.},
language = {Anglais},
booktitle = {Proceeding of ICEAA on IEEE},
doi = {10.1109/ICEAA.2016.7731490},
year = {2016},
url = {http://hdl.handle.net/2078.1/181533}}``````

• A. Vallecchi, S. Hubert, A. Schuchinsky, and C. Craeye, “Phase Gradient Discontinuity Metasurface with Intertwined Spiral Arrays.” 2016.

A reflect-type metasurface with phase gradient discontinuity is proposed. It is formed by planar intertwined spiral conductors loaded with inductors. A pattern of conductors is initially designed under the assumption of locally periodicity and the phase response of uniform arrays. Simulations are performed with a fast proprietary code based on the periodic Method of Moment and the Array Scanning Method. Macro-cells, containing 70 identical micro-cells with different loads, have been analysed, and it is found that the reflected power only partially goes into the desired non-specular Floquet mode.

``````@inproceedings{boreal:195108,
title = {Phase Gradient Discontinuity Metasurface with Intertwined Spiral Arrays},
author = {Andrea Vallecchi and Hubert, Simon and Alex Schuchinsky and Craeye, Christophe},
abstract = {A reflect-type metasurface with phase gradient discontinuity is proposed. It is formed by planar intertwined spiral conductors loaded with inductors. A pattern of conductors is initially designed under the assumption of locally periodicity and the phase response of uniform arrays. Simulations are performed with a fast proprietary code based on the periodic Method of Moment and the Array Scanning Method. Macro-cells, containing 70 identical micro-cells with different loads, have been analysed, and it is found that the reflected power only partially goes into the desired non-specular Floquet mode.},
Keywords = {reflector , metasurface , antenna , array},
language = {Anglais},
year = {2016},
url = {http://hdl.handle.net/2078.1/195108}}``````

• Q. Gueuning, C. Craeye, and C. Oestges, “Unequally-spaced fast Laplace transform for Green’s function evaluation,” in Proceedings 2016 URSI International Symposium on Electromagnetic Theory (EMTS), 2016. doi:10.1109/URSI-EMTS.2016.7571477 10.1109/URSI-EMTS.2016.7571477

A fast method for the radiation analysis of arbitrary oriented planes is presented. It combines an adaptive spectral integration scheme and a recently proposed unequally-spaced fast Laplace transform algorithm. It is illustrated on the free-space Green’s function through an example where an important speed-up factor is evaluated compared to the brute force spectral integration.

``````@inproceedings{boreal:179920,
title = {Unequally-spaced fast Laplace transform for Green's function evaluation},
author = {Gueuning, Quentin and Craeye, Christophe and Oestges, Claude},
abstract = {A fast method for the radiation analysis of arbitrary oriented planes is presented. It combines an adaptive spectral integration scheme and a recently proposed unequally-spaced fast Laplace transform algorithm. It is illustrated on the free-space Green's function through an example where an important speed-up factor is evaluated compared to the brute force spectral integration.},
Keywords = {ICTEAM:COMM},
language = {Anglais},
booktitle = {Proceedings 2016 URSI International Symposium on Electromagnetic Theory (EMTS)},
doi = {10.1109/URSI-EMTS.2016.7571477 10.1109/URSI-EMTS.2016.7571477},
year = {2016},
url = {http://hdl.handle.net/2078.1/179920}}``````