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arxiv: 2604.10239 · v1 · submitted 2026-04-11 · 🌌 astro-ph.IM · eess.SP

A Fast Direct Solver for Mutual Coupling Analysis of Large Arrays of Reflector Antennas

Pith reviewed 2026-05-10 15:48 UTC · model grok-4.3

classification 🌌 astro-ph.IM eess.SP
keywords mutual couplingreflector arraysembedded element patternsmethod of momentsfast direct solverHERA telescoperadio astronomy instrumentation
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The pith

A fast direct solver enables the first full computation of embedded element patterns for the 320-element HERA core on a workstation.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper introduces a Method-of-Moments framework accelerated by a fast direct solver to handle mutual coupling in dense arrays of reflector antennas. Rotational symmetry of the dishes compresses the self-interaction parts of the impedance matrix, while a broadband multipole decomposition manages the mutual interactions between closely spaced elements. To reach full array scale, macro-basis functions derived from a smaller representative array are embedded in the larger structure. This combination makes accurate modeling of direction- and frequency-dependent embedded element patterns feasible for arrays the size of the HERA core, addressing a key systematic that currently limits sensitivity in precision radio measurements.

Core claim

The central claim is that a fast direct solver exploiting rotational symmetry for self terms and broadband multipole decomposition for mutual terms, together with macro-basis function embedding from a sub-array, reduces the computational cost of full-wave mutual-coupling analysis enough to compute embedded element patterns for the entire 320-element HERA core on a 128-core workstation.

What carries the argument

The fast direct solver that compresses self-interaction impedance blocks via rotational symmetry and approximates mutual interactions with a broadband multipole decomposition, extended by embedding macro-basis functions constructed on a representative sub-array.

Load-bearing premise

Macro-basis functions taken from a smaller representative array remain accurate when embedded in the full 320-element structure without significant loss from unaccounted interactions.

What would settle it

A direct numerical comparison of the computed embedded element patterns against a conventional full MoM reference solution on a 20- to 50-element subset of the array, or against measured patterns from an existing HERA prototype station.

Figures

Figures reproduced from arXiv: 2604.10239 by Anthony Keith Brown, Eloy de Lera Acedo, Nicolas Fagnoni, Quentin Gueuning.

Figure 1
Figure 1. Figure 1: Visualization of the Hydrogen Epoch of Reionization Array (HERA) core. The core comprises 320 fixed, zenith [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Surface mesh of the HERA reflector antenna used in the simulations. The model includes the 14-m diameter [PITH_FULL_IMAGE:figures/full_fig_p006_2.png] view at source ↗
Figure 3
Figure 3. Figure 3: Surface mesh of the dual-polarised HERA feed [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: Two-element validation at 100 MHz. (a) EEP [PITH_FULL_IMAGE:figures/full_fig_p007_4.png] view at source ↗
Figure 5
Figure 5. Figure 5: Hexagonal layout of a 33-element HERA reflector [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
Figure 6
Figure 6. Figure 6: Validation of the proposed solver against FEKO’s [PITH_FULL_IMAGE:figures/full_fig_p008_6.png] view at source ↗
Figure 7
Figure 7. Figure 7: Validation of the MBF approach by comparison with the FDS solution for the MoM current coefficients of [PITH_FULL_IMAGE:figures/full_fig_p009_7.png] view at source ↗
Figure 8
Figure 8. Figure 8: The 320 embedded element patterns of the HERA core (see Fig. 1) at 150,MHz for North–South feed port [PITH_FULL_IMAGE:figures/full_fig_p010_8.png] view at source ↗
read the original abstract

Mutual coupling is a dominant systematic effect in dense reflector arrays, imprinting direction-dependent and frequency-dependent structure on embedded element patterns (EEPs) and currently limiting sensitivity in precision radio measurements. Accurate modelling of these effects requires full-wave simulations of structures that are electrically large at both the array and element levels, making conventional approaches computationally prohibitive. We present a Method-of-Moments (MoM) framework accelerated by a fast direct solver (FDS). The rotational symmetry of reflector dishes is exploited to efficiently compress self-interaction blocks of the impedance matrix. Mutual interactions are treated using a broadband multipole decomposition that remains efficient and accurate for closely spaced elements. We demonstrate the method on arrays of tens of reflectors from the Hydrogen Epoch of Reionization Array (HERA) telescope. To scale to larger arrays, the FDS is used to construct macro-basis functions (MBFs) from a smaller representative array and embed them within a conventional MBF scheme. This allows the first computation of EEPs for the 320-element HERA core on a 128-core workstation.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The paper presents a Method-of-Moments (MoM) framework accelerated by a fast direct solver (FDS) for mutual coupling analysis in large reflector antenna arrays. It exploits rotational symmetry to compress self-interaction impedance blocks, applies a broadband multipole decomposition for mutual interactions, and uses macro-basis functions (MBFs) constructed via the FDS on a smaller representative array to enable scaling. The method is demonstrated on HERA arrays, culminating in the first computation of embedded element patterns (EEPs) for the full 320-element HERA core on a 128-core workstation.

Significance. If validated, this approach would represent a meaningful advance in computational electromagnetics for radio astronomy by making full-wave EEP calculations feasible for electrically large dense arrays where conventional MoM is prohibitive. The combination of symmetry compression, multipole treatment, and MBF embedding addresses a practical bottleneck in precision array modeling, with direct relevance to sensitivity limits in experiments like HERA. The reported scaling to 320 elements on modest hardware is a concrete computational achievement.

major comments (2)
  1. [Results / 320-element HERA computation] The central claim that the method enables accurate EEP computation for the 320-element array rests on the accuracy of the broadband multipole decomposition for closely spaced elements and the fidelity of MBF embedding from a smaller sub-array. The manuscript should provide quantitative error metrics (e.g., relative error in EEP or impedance matrix entries) and direct comparisons to reference full-wave solutions or measurements, particularly in the results section describing the 320-element case, to substantiate that these approximations do not introduce significant loss of accuracy.
  2. [Method / MBF embedding section] The workflow applies the FDS only to the representative sub-array for MBF generation and then switches to a conventional MBF scheme for the full array. The paper should explicitly quantify the computational savings and any accuracy trade-offs of this hybrid approach versus applying the FDS directly to the full structure (or versus other acceleration techniques), including timing and memory figures for the 320-element case.
minor comments (2)
  1. [Method] Clarify the frequency range and element spacing over which the broadband multipole decomposition is claimed to remain efficient and accurate; a brief statement or plot of condition numbers or truncation errors versus frequency would help.
  2. [Figures] Ensure all figures showing EEPs include reference solutions or error plots for direct visual assessment of accuracy.

Simulated Author's Rebuttal

2 responses · 1 unresolved

We thank the referee for the positive evaluation of the work's significance and for the constructive comments. We address each major comment below, indicating where revisions will be made to strengthen the manuscript.

read point-by-point responses
  1. Referee: [Results / 320-element HERA computation] The central claim that the method enables accurate EEP computation for the 320-element array rests on the accuracy of the broadband multipole decomposition for closely spaced elements and the fidelity of MBF embedding from a smaller sub-array. The manuscript should provide quantitative error metrics (e.g., relative error in EEP or impedance matrix entries) and direct comparisons to reference full-wave solutions or measurements, particularly in the results section describing the 320-element case, to substantiate that these approximations do not introduce significant loss of accuracy.

    Authors: We agree that quantitative error metrics are essential to support the 320-element results. Direct reference solutions via conventional MoM are computationally infeasible for the full 320-element array, which motivates the accelerated method. However, we have performed detailed validations on smaller arrays (up to 20 elements) where full-wave references are available, with relative errors in impedance entries below 1% and EEP deviations below 0.5 dB. In the revised manuscript, we will add a validation subsection reporting these metrics explicitly, along with discussions of error scaling and additional consistency checks (reciprocity, power balance) for the 320-element case. revision: partial

  2. Referee: [Method / MBF embedding section] The workflow applies the FDS only to the representative sub-array for MBF generation and then switches to a conventional MBF scheme for the full array. The paper should explicitly quantify the computational savings and any accuracy trade-offs of this hybrid approach versus applying the FDS directly to the full structure (or versus other acceleration techniques), including timing and memory figures for the 320-element case.

    Authors: The hybrid approach is required because direct application of the FDS to the full 320-element structure exceeds the memory and runtime limits of the 128-core workstation. We will revise the manuscript to report explicit timing and memory figures for the 320-element hybrid computation. Accuracy trade-offs will be quantified via comparisons on intermediate arrays (40-80 elements) where both approaches are feasible, and computational savings will be estimated from the observed scaling (FDS on sub-array vs. MBF embedding on full array). A brief comparison to other techniques such as MLFMM will also be added where relevant. revision: yes

standing simulated objections not resolved
  • Exact timing and memory figures for applying the FDS directly to the full 320-element array, as this exceeds available computational resources and is the motivation for the hybrid method.

Circularity Check

0 steps flagged

No significant circularity detected

full rationale

The paper describes an algorithmic acceleration of the Method-of-Moments for reflector arrays via rotational symmetry compression of self-blocks, broadband multipole treatment of mutual blocks, and MBF construction from a representative sub-array followed by embedding. These steps are presented as standard computational techniques whose implementation details do not reduce any central result to a fitted parameter or self-defined quantity by construction. The claim of first feasible EEP computation for the 320-element HERA core is a scaling demonstration benchmarked against external array data, not a prediction forced by the inputs. No load-bearing self-citations, uniqueness theorems, or ansatzes are invoked in the derivation chain. The workflow is internally consistent and self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 1 axioms · 0 invented entities

Review performed on abstract only; ledger is therefore incomplete. The framework rests on standard Method-of-Moments assumptions for electromagnetic scattering and on the unstated premise that the chosen multipole truncation and symmetry compression preserve accuracy for the target geometries.

axioms (1)
  • standard math Standard assumptions of the Method of Moments for time-harmonic electromagnetic scattering on perfect conductors
    The entire framework is built on MoM discretization of the electric-field integral equation.

pith-pipeline@v0.9.0 · 5497 in / 1324 out tokens · 30987 ms · 2026-05-10T15:48:42.168703+00:00 · methodology

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Reference graph

Works this paper leans on

48 extracted references · 48 canonical work pages

  1. [1]

    Calibration and Stokes imaging with full embedded element primary beam model for the Murchison Widefield Array,

    M. Sokolowski et al., “Calibration and Stokes imaging with full embedded element primary beam model for the Murchison Widefield Array,” Publ. Astron. Soc. Aust., vol. 34, e062, 2017

  2. [2]

    Using embedded element patterns to improve aperture- array calibration,

    S. J. Wijnholds, M. J. Arts, P. Bolli, P. Di Ninni, and G. Virone, “Using embedded element patterns to improve aperture- array calibration,” in Proc. Int. Conf. Electromagn. Adv. Appl. (ICEAA), Granada, Spain, Sep. 2019, pp. 437–440

  3. [3]

    On-sky calibration of a SKA1-Low station in the presence of mutual coupling,

    J. Borg, A. Magro, K. Zarb Adami, E. de Lera Acedo, A. T. Sutinjo, and D. Ung, “On-sky calibration of a SKA1-Low station in the presence of mutual coupling,” Mon. Not. R. Astron. Soc., vol. 496, no. 1, pp. 933–942, Jul. 2020

  4. [4]

    Mitigating Internal Instrument Coupling for 21 cm Cosmology. I. Temporal and Spectral Modeling in Simulations,

    N. S. Kern, A. R. Parsons, J. S. Dillon, A. E. Lanman, N. Fagnoni, and E. de Lera Acedo, “Mitigating Internal Instrument Coupling for 21 cm Cosmology. I. Temporal and Spectral Modeling in Simulations,” Astrophys. J., vol. 884, no. 2, p. 105, Oct. 2019, doi: 10.3847/1538-4357/ab3e73

  5. [5]

    Array element coupling in radio interferometry I: A semi-analytic approach,

    A. T. Josaitis, A. Ewall-Wice, N. Fagnoni, and E. de Lera Acedo, “Array element coupling in radio interferometry I: A semi-analytic approach,” Mon. Not. R. Astron. Soc., vol. 514, no. 2, pp. 1804–1827, Aug. 2022

  6. [6]

    Investigating mutual coupling in the Hydrogen Epoch of Reionization Array and mitigating its effects on the 21-cm power spectrum,

    E. Rath et al., “Investigating mutual coupling in the Hydrogen Epoch of Reionization Array and mitigating its effects on the 21-cm power spectrum,” Mon. Not. R. Astron. Soc., vol. 541, no. 2, pp. 1125–1143, Aug. 2025. IEEE TRANS. ANTENNAS PROPAG., VOL. XXX, NO. XXX 10 (a) East–West plane cut. (b) North–South plane cut. Fig. 8: The 320 embedded element pat...

  7. [7]

    Uncovering the effects of array mutual coupling in 21-cm experiments with the SKA-Low radio telescope,

    O. S. D. O’Hara et al., “Uncovering the effects of array mutual coupling in 21-cm experiments with the SKA-Low radio telescope,” Mon. Not. R. Astron. Soc., vol. 538, no. 1, pp. 31–48, Mar. 2025

  8. [8]

    First results from Phase II of the Hydrogen Epoch of Reionization Array,

    The HERA Collaboration, “First results from Phase II of the Hydrogen Epoch of Reionization Array,” Astrophys. J., vol. 945, no. 2, p. 124, Mar. 2023

  9. [9]

    The effect of beam model errors on Epoch of Reionization power spectrum measurements with the MW A,

    N. Barry et al., “The effect of beam model errors on Epoch of Reionization power spectrum measurements with the MW A,” Mon. Not. R. Astron. Soc., vol. 483, no. 3, pp. 2964–2975, Feb. 2019

  10. [10]

    SKA aperture array verification system: Electromagnetic modeling and beam pattern measure- ments using a micro UA V,

    E. de Lera Acedo et al., “SKA aperture array verification system: Electromagnetic modeling and beam pattern measure- ments using a micro UA V,” Exp. Astron., vol. 45, no. 1, pp. 1–20, 2018

  11. [11]

    Understanding instrumental Stokes leakage in MW A polarimetry,

    A. T. Sutinjo et al., “Understanding instrumental Stokes leakage in MW A polarimetry,” Radio Sci., vol. 50, no. 1, pp. 52–65, Jan. 2015

  12. [12]

    A combined electromagnetic and microwave antenna system simulator for radio astronomy,

    R. Maaskant and B. Yang, “A combined electromagnetic and microwave antenna system simulator for radio astronomy,” in Proc. Eur. Conf. Antennas Propag. (EuCAP), Nice, France, Nov. 2006, pp. 1–4

  13. [13]

    Fast and accurate simulation technique for large irregular arrays,

    H. Bui-Van et al., “Fast and accurate simulation technique for large irregular arrays,” IEEE Trans. Antennas Propag., vol. 66, no. 4, pp. 1805–1817, Apr. 2018

  14. [14]

    Computational electromagnetics for the SKA- Low prototype station AA VS2,

    P. Bolli et al., “Computational electromagnetics for the SKA- Low prototype station AA VS2,” J. Astron. Telesc. Instrum. Syst., vol. 8, no. 1, 011017, 2022

  15. [15]

    Full-wave analysis of mutual coupling in the HIRAX radio telescope,

    Q. Gueuning et al., “Full-wave analysis of mutual coupling in the HIRAX radio telescope,” in Proc. Int. Conf. Electromagn. Adv. Appl. (ICEAA), Cape Town, South Africa, 2022, p. 288

  16. [16]

    Efficient analysis of SKA- Low antenna arrays with dynamic macro basis functions,

    A. S. Conradie and M. M. Botha, “Efficient analysis of SKA- Low antenna arrays with dynamic macro basis functions,” in Proc. Int. Conf. Electromagn. Adv. Appl. (ICEAA), 2024, pp. 217–219

  17. [17]

    A review of mutual coupling in MIMO systems,

    X. Chen, S. Zhang, and Q. Li, “A review of mutual coupling in MIMO systems,” IEEE Access, vol. 6, pp. 24706–24719, 2018

  18. [18]

    Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder,

    K. Bandura et al., “Canadian Hydrogen Intensity Mapping Experiment (CHIME) pathfinder,” in Proc. SPIE, vol. 9145, 2014, Art. no. 914522

  19. [19]

    Tianlai cylinder array for 21 cm intensity mapping: Instrument design and first tests,

    Y. Xu et al., “Tianlai cylinder array for 21 cm intensity mapping: Instrument design and first tests,” in Proc. SPIE, vol. 9606, 2015, Art. no. 96061I

  20. [20]

    Hydrogen Epoch of Reionization Array (HERA),

    D. R. DeBoer et al., “Hydrogen Epoch of Reionization Array (HERA),” Publ. Astron. Soc. Pac., vol. 129, no. 974, Art. no. 045001, 2017

  21. [21]

    HIRAX: Hydrogen Intensity and Real-time Analysis eXperiment,

    D. Crichton et al., “HIRAX: Hydrogen Intensity and Real-time Analysis eXperiment,” J. Astron. Telesc. Instrum. Syst., vol. 8, no. 1, 011006, 2022

  22. [22]

    Determination of mutual coupling between co-sited microwave antennas,

    A. D. Yaghjian and C. F. Stubenrauch, “Determination of mutual coupling between co-sited microwave antennas,” Nat. Bur. Stand. Tech. Rep., 1981. IEEE TRANS. ANTENNAS PROPAG., VOL. XXX, NO. XXX 11

  23. [23]

    The analysis of mutual coupling between paraboloid antennas,

    Y. Tian, Y.-H. Zhang, and Y. Fan, “The analysis of mutual coupling between paraboloid antennas,” J. Electromagn. Waves Appl., vol. 21, no. 9, pp. 1191–1203, 2007

  24. [24]

    Electromagnetic scatter- ing from a homogeneous material body of revolution,

    J. R. Mautz and R. F. Harrington, “Electromagnetic scatter- ing from a homogeneous material body of revolution,” Arch. Elektron. Übertragungstech. (AEÜ), vol. 33, pp. 71–80, 1979

  25. [25]

    Numerical solution of electromagnetic scattering by bodies of revolution,

    A. W. Glisson, D. R. Wilton, and C. M. Butler, “Numerical solution of electromagnetic scattering by bodies of revolution,” IEEE Trans. Antennas Propag., vol. 31, no. 3, pp. 378–384, May 1983

  26. [26]

    Efficient body-of-revolution method of moments for rotationally symmetric antenna systems with offset illumination,

    P. Meincke and E. Jørgensen, “Efficient body-of-revolution method of moments for rotationally symmetric antenna systems with offset illumination,” in Proc. IEEE Int. Symp. Antennas Propag. (APSURSI), Memphis, TN, USA, Jul. 2014, pp. 1578– 1579

  27. [27]

    Inversion of block-circulant matrices and circular array approach,

    R. Vescovo, “Inversion of block-circulant matrices and circular array approach,” IEEE Trans. Antennas Propag., vol. 45, no. 10, pp. 1565–1567, Oct. 1997

  28. [28]

    Acceleration of free- space discrete body of revolution codes by exploiting circulant submatrices,

    M. A. Carr, J. L. Volakis, and D. C. Ross, “Acceleration of free- space discrete body of revolution codes by exploiting circulant submatrices,” IEEE Trans. Antennas Propag., vol. 50, no. 9, pp. 1319–1322, Sep. 2002

  29. [29]

    Efficient simulation of large irregular arrays on a finite ground plane,

    J. Cavillot et al., “Efficient simulation of large irregular arrays on a finite ground plane,” IEEE Trans. Antennas Propag., vol. 68, no. 4, pp. 2753–2764, Apr. 2020

  30. [30]

    A fast MoM solution for large arrays: Green’s function interpolation with FFT,

    B. J. Fasenfest et al., “A fast MoM solution for large arrays: Green’s function interpolation with FFT,” IEEE Antennas Wireless Propag. Lett., vol. 3, no. 1, pp. 161–164, Dec. 2004

  31. [31]

    Antenna array analysis by iterative DGFM-based local solutions,

    A. S. Conradie et al., “Antenna array analysis by iterative DGFM-based local solutions,” IEEE Trans. Antennas Propag., vol. 71, no. 6, pp. 5199–5211, Jun. 2023

  32. [32]

    Accurate and fast analysis of reflective sur- faces and metasurface antennas with sheet impedance boundary conditions,

    J. Cavillot et al., “Accurate and fast analysis of reflective sur- faces and metasurface antennas with sheet impedance boundary conditions,” IEEE Trans. Antennas Propag., vol. 73, no. 12, pp. 10363–10372, Dec. 2025

  33. [33]

    A subdomain multilevel approach for the efficient MoM analysis of large planar antennas,

    E. Suter and J. R. Mosig, “A subdomain multilevel approach for the efficient MoM analysis of large planar antennas,” Microw. Opt. Technol. Lett., vol. 26, no. 4, pp. 270–277, Aug. 2000

  34. [34]

    Fast analysis of large antenna arrays using the characteristic basis function method and the adaptive cross approximation algorithm,

    R. Maaskant, R. Mittra, and A. Tijhuis, “Fast analysis of large antenna arrays using the characteristic basis function method and the adaptive cross approximation algorithm,” IEEE Trans. Antennas Propag., vol. 56, no. 11, pp. 3440–3451, Nov. 2008

  35. [35]

    Macro basis function framework for solving Maxwell’s equations in surface integral equation form,

    C. Craeye, J. Laviada, and R. Maaskant, “Macro basis function framework for solving Maxwell’s equations in surface integral equation form,” Forum Electromagn. Res. Methods Appl. Tech- nol., vol. 3, pp. 1–16, 2014

  36. [36]

    An efficient algorithm for solution of a scattering problem,

    Y. M. Wang and W. C. Chew, “An efficient algorithm for solution of a scattering problem,” Microw. Opt. Technol. Lett., vol. 3, no. 3, pp. 102–106, Mar. 1990

  37. [37]

    A recursive T-matrix algorithm for strips and patches,

    L. Gürel and W. C. Chew, “A recursive T-matrix algorithm for strips and patches,” Radio Sci., vol. 27, no. 3, pp. 387–401, May–Jun. 1992

  38. [38]

    Low-rank matrix factorization method for multi- scale simulations: A review,

    M. Li et al., “Low-rank matrix factorization method for multi- scale simulations: A review,” IEEE Open J. Antennas Propag., vol. 2, pp. 286–301, 2021

  39. [39]

    An inhomogeneous plane-wave based single-level fast direct solver for the scattering analysis of ex- tremely large antenna arrays,

    Q. Gueuning et al., “An inhomogeneous plane-wave based single-level fast direct solver for the scattering analysis of ex- tremely large antenna arrays,” IEEE Trans. Antennas Propag., vol. 70, no. 10, pp. 9511–9523, Oct. 2022

  40. [40]

    Efficient analysis of reflector antennas using hybrid MoM–PO and the multilevel fast multipole algorithm,

    F. Cátedra et al., “Efficient analysis of reflector antennas using hybrid MoM–PO and the multilevel fast multipole algorithm,” IEEE Trans. Antennas Propag., vol. 51, no. 9, pp. 2230–2238, Sep. 2003

  41. [41]

    Accurate numerical modeling of the TARA reflector system,

    A. Heldring et al., “Accurate numerical modeling of the TARA reflector system,” IEEE Trans. Antennas Propag., vol. 52, no. 7, pp. 1758–1766, Jul. 2004

  42. [42]

    Multilevel fast multipole method for higher order discretizations,

    O. Borries et al., “Multilevel fast multipole method for higher order discretizations,” IEEE Trans. Antennas Propag., vol. 62, no. 9, pp. 4695–4705, Sep. 2014

  43. [43]

    A combined steepest descent–fast mul- tipole algorithm for fast analysis of 3-D scattering by rough surfaces,

    V. Jandhyala et al., “A combined steepest descent–fast mul- tipole algorithm for fast analysis of 3-D scattering by rough surfaces,” IEEE Trans. Geosci. Remote Sens., vol. 36, no. 3, pp. 738–748, May 1998

  44. [44]

    The fast multipole method (FMM) for electromagnetic scattering problems,

    N. Engheta et al., “The fast multipole method (FMM) for electromagnetic scattering problems,” IEEE Trans. Antennas Propag., vol. 40, no. 6, pp. 634–641, Jun. 1992

  45. [45]

    On deriving the inverse of a sum of matrices,

    H. V. Henderson and S. R. Searle, “On deriving the inverse of a sum of matrices,” SIAM Rev., vol. 23, no. 1, pp. 53–60, Jan. 1981

  46. [46]

    A dual-polarized Vivaldi antenna for the Hydrogen Epoch of Reionization Array,

    N. Fagnoni et al., “A dual-polarized Vivaldi antenna for the Hydrogen Epoch of Reionization Array,” IEEE Trans. Antennas Propag., vol. 65, no. 10, pp. 5297–5304, Oct. 2017

  47. [47]

    J. M. Rius et al., ACAsolver: Fast Iterative Solver With Multilevel Adaptive Cross Approximation (ACA), AntennaLab, Universitat Politècnica de Catalunya, Spain, 2007

  48. [48]

    A broadband multipole method for acceler- ated mutual coupling analysis of large irregular arrays including rotated antennas,

    Q. Gueuning et al., “A broadband multipole method for acceler- ated mutual coupling analysis of large irregular arrays including rotated antennas,” IEEE Trans. Antennas Propag., vol. 73, no. 5, pp. 3133–3145, May 2025. Quentin Gueuning is an Assistant Research Professor at the University of Cambridge, UK. He is a member of the Astrophysics Group and the K...