Groove-Gap-Waveguide Technology for RF Filters: Recent Advances and Design Trends

This review article aims to offer a comprehensive overview of recent advances in field of RF filtering devices based on groove-gap-waveguide (GGW) technology. Particular focus is placed on millimeter-wave high-selectivity bandpass filters (BPFs) featuring multiple out-of-band TZs, achieved through a variety of RF operational mechanisms. The discussion spans from well-established design strategies, such as cross-coupled-resonator configurations, to cutting-edge approaches that exploit the concept of input reactive load or frequency-variant coupling. Both single-and dual-band BPF implementations are explored, encompassing designs with reflective and reflectionless characteristics. Potential trends and future directions for GGW-based RF filtering components for emerging wireless applications are also outlined.