Compact Single‐Cavity Dual‐Band SIW Filter Based on Orthogonal Hybrid Loading

ABSTRACT

A compact, high‐selectivity, dual‐band substrate‐integrated waveguide (SIW) filter is proposed in this paper based on an orthogonal hybrid loading scheme. To address the inherent trade‐off among circuit size, frequency selectivity and tuning flexibility in conventional single‐cavity dual‐band SIW designs, two symmetrical capacitive conductive posts and three central inductive metallised vias are orthogonally integrated into a single cavity to reconstruct the first four resonant modes for dual‐passband operation. The capacitive posts modulate higher‐order resonant modes to support mode reconstruction, lowering the lower passband frequency for miniaturisation and quasi‐independent tuning. The inductive vias regulate the inter‐mode coupling strength to generate two controllable transmission zeros and achieve independent bandwidth adjustment for both passbands. A filter prototype is implemented using the multilayer PCB process. It occupies a compact footprint of 0.76 λg ² and operates at 5.48 and 8.36 GHz with 3‐dB fractional bandwidths of 3.8% and 5%, respectively.