Novel Configuration of an Elliptic Waveguide Filter Using TE 103 Mode for the Q-Band OMUX

This letter presents a three-channel Q-band output multiplexer (OMUX) based on pseudo-elliptic$T\!E_{103}$-mode waveguide filters with diagonal cross coupling. The elliptic-function condition is derived using a coupling-matrix formulation, and the proposed structure is shown to satisfy the required coupling relationships. A folded resonator configuration is introduced to realize the cross-coupling while maintaining a compact structure. The OMUX operates with three channels centered from 37.9 to 39.5 GHz, each providing a 700 MHz bandwidth. An efficient design procedure combining equivalent-circuit optimization and full-wave 3-D electromagnetic (EM) simulation is employed, significantly reducing the design time. Measurements of the fabricated prototype show good agreement with simulations, achieving an in-band return loss better than 20 dB, out-of-band rejection exceeding 18 dB at a 100 MHz offset, and a minimum insertion loss of 0.5 dB. The proposed approach provides a compact and thermally efficient Q-band OMUX solution suitable for satellite payload applications.