Dual-Band, Dual-Mode, Microstrip Resonator Loaded, Compact Hybrid SIW Bandpass Filter

This paper proposes a novel dual-band and dual-mode hybrid substrate integrated waveguide (SIW) filter with a compact dimension and controllable frequency ratio. The hybrid SIW with a completely closed structure combines a double-layer SIW cavity and two microstrip line resonators. By using this hybrid cavity structure, size reduction and controllable dual-band response are simultaneously achieved. The low frequency passband is realized by combing TE101 mode and microstrip resonator and the high frequency passband is formed by TE201 mode. To improve the selectively, the filter is configured with transmission zeros (TZs) nearby the passband by the cross coupling and the mixed coupling. The filter was fabricated and measured, showing consistent filtering responses compared with simulations. The proposed filter has the merits of a miniaturized size, low insertion loss, high selectivity, and wide stopband.