Design and Research of a W-Band Waveguide Filter with CQ Coupling

The expansion of fifth-generation communications, millimeter-wave radar, satellite systems, and future 6G technologies into millimeter-wave and terahertz frequencies highlights the growing demand for advanced filtering solutions. The W-band (75–110 GHz), known for its wide bandwidth and high-resolution capabilities, is particularly critical for high-speed wireless communications and precision sensing. However, conventional printed-circuit filters suffer from excessive losses in this range, making low-loss, high-power alternatives essential. This paper presents a compact four-cavity W-band waveguide filter based on a cascaded-quadruplet (CQ) cross-coupling structure. The proposed design operates from 83GHz to 90GHz, achieving in-band insertion loss below 0.15dB and return loss better than 16dB. By reducing cavity count while maintaining performance, the filter offers improved integration and practical utility for next-generation millimeter-wave systems.