Two-Way Waveguide Diplexer and Its Application to Diplexing In-Band Full-Duplex Antenna

A design of a diplexing in-band full-duplex (IBFD) slot antenna based on the quadruple-mode resonator (QMR) is presented for the first time. First, a two-way waveguide diplexer integration using QMR is designed. Four waveguide modes, namely, TE011, TE101, TM210, and TM120, are primarily used. These four modes are modal orthogonal to each other in a single QMR. Each of the quadruple modes can be independently manipulated with low mutual interference with other modes. Taking advantage of this characteristic, a two-way waveguide diplexer integration can be implemented with four independent frequency channels. In each diplexer, the downlink channel is dominated by fundamental mode TE011, TE101, while the uplink channel is dominated by high-order mode TM210/TM120. By cascading QMRs, higher order frequency responses are achieved with expected coupling coefficient (K) and external quality factor (Q(e)). Based on the proposed two-way diplexer concept, a diplexing IBFD antenna with a turnstile junction is designed by replacing the inputs with a cross-coupled radiating slot. It integrates the filtering, diplexing, orthomode transducing, and radiating functions into a single element. Four channels can work independently to transmit/receive two orthogonal signals. The two-way waveguide diplexer and diplexing IBFD waveguide antenna with a second-order response were implemented and tested for the proof-of-concept.

Automated summary

In this paper, a design of a diplexing in-band full-duplex (IBFD) slot antenna based on the quadruple-mode resonator (QMR) is presented for the first time. By using the QMR as a two-way waveguide diplexer integration, four independent frequency channels are implemented in the antenna. Higher order frequency responses are achieved by cascading QMRs. The antenna integrates filtering, diplexing, orthomode transducing, and radiating functions into a single element.