S-Parameter-Based Theoretical Analysis of a Matching Network for Generic Multiport Antennas

This article describes a general method for finding an S-parameter of a matching network converting between arbitrary passive reciprocal multiport electrical circuits with the same amount of ports. In particular, the application to multiport antennas is explored. A quality of the matching is shown on a simulated 73 GHz 16-element 0.4λ-spaced bow-tie linear array, with its matched optimum realized gain achieving the theoretical maximum of the optimal gain over the [-π/2,π/2] scanning arc and showing a 5 dB improvement over the unmatched case. Degrees of freedom describing different matching network's realizations with the proposed method are enumerated, and their utilization for the transmitter amplifiers back-off reduction are presented. A fitness of the obtained matching network S-parameter for the conversion into a physical design is explored, and a practical method of obtaining a robust, feasibly realizable solution is given. The proposed network is estimated to require a quality factor 100 or better and demonstrates the useful bandwidth of 2 GHz and a good performance even with the coupling compensation reduced only to the neighboring ports.