Dual and triple mode groove gap waveguide filters for high-power low-loss mm-wave SATCOM applications

The Groove Gap Waveguide (GGW) technology has emerged as the foremost candidate for realizing filters in millimeter-wave (mm-Wave) frequency bands. For satellite communication, multi-mode (dual and triple mode) filters are the need of the hour in view of stringent specifications and compact footprint requirement. This paper introduces a comprehensive design of multi-mode filters (dual and triple-mode filters) using groove gap waveguide technology for high-power SATCOM applications at Q-band (38 GHz). Inter-modal couplings are realized using square corner-cut structures for both Chebyshev and quasi-elliptic filters (in cascaded triplet as well as in cascaded quadruplet topologies) and are discussed in detail. A novel design for triple-mode 6-pole quasi-elliptic filter in cascaded quadruplet topology is presented. This design critically employs Virtual Negative Coupling (VNC) to generate the required transmission zeros (TZs), thus ensuring optimal selectivity. Furthermore, the strategic use of separate inter-cavity coupling irises are introduced to decouple the tuning variables, which significantly enhances design flexibility and provides independent control over the coupling coefficients. The paper addresses all the practically useful variants of multi-mode filters that are potential candidates for high-power filters in next-generation SATCOM applications. This work validates the practical viability of high-power GGW multi-mode filters. Experimental results are provided through the successful fabrication and measurement of both four-pole dual-mode Chebyshev filter and the novel six-pole triple-mode quasi-elliptic filter. The measured results are in good agreement with the full-wave electro-magnetic simulation results.