A.O. Zajkov1, D.V. Klyukin2, A.A. Ivanov3, S.P. Kuksenko4

1–4 Tomsk State University of Control Systems and Radioelectronics (Tomsk, Russia)

1 artem.o.zaikov@tusur.ru; 2 dmitrii.v.kliukin@tusur.ru; 3 anton.a.ivanov@tusur.ru; 4 sergei.p.kuksenko@tusur.ru

Problem statement. Modern microwave devices are often complex multi-port structures incorporating lumped loads that require accurate modeling of scattering parameters, their optimization, and impedance matching within computer-aided design (CAD) systems, particularly using the Method of Moments (MoM). However, the specific aspects of computing scattering parameters via MoM –accounting for both active and passive ports as well as various types of lumped loads – are insufficiently addressed in the existing literature. This work fills that gap. Moreover, current methods for optimizing the complex load impedance to minimize reflections in microwave structures typically rely on a single basis function (BF) at the load edge, which restricts their applicability to problems with fine mesh discretization. To overcome this limitation, we propose an optimization algorithm based on the Sherman-Morrison-Woodbury formula. This approach enables rapid computation of surface currents accounting for the complex load impedance and supports an arbitrary number of BF associated with the load edge.

The purpose of the work. To develop an algorithm for optimizing the complex impedance of a load element with an arbitrary number of BFs on its edge, ensuring matching of the port’s internal resistance with a multi-port structure in the MoM framework.

Results. We describe a MoM-based procedure for computing scattering parameters in problems with active/passive ports and different types of lumped loads, and we verify our MoM solver on four microwave models. The deviation from a third-party MoM solver does not exceed 0.82 dB. Feature selective validation method shows that more than 40% of the data points fall into the “Excellent” category. We also propose a load-impedance optimization algorithm that minimizes the reflection coefficient by matching the port internal resistance to the structure’s input impedance. The algorithm’s performance is demonstrated on three microstrip structures, where the average reduction of the reflection level is about 90 dB.

Practical significance. The proposed algorithm can be integrated into CAD tools for the design of antennas and microwave devices.

The research was carried out at the expense of Russian Science Foundation grant 23-79-10165, https://rscf.ru/project/23-79-10165/.

Zajkov A.O., Klyukin D.V., Ivanov A.A., Kuksenko S.P. On computing scattering parameters of multi-port microwave devices with the method of moments. Radiotekhnika. 2026. V. 90. № 4. P. 165−179. DOI: https://doi.org/10.18127/j00338486-202604-19 (In Russian)

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