Metal-Dielectric Coaxial Dual-mode Resonator for Compact Inline Bandpass Filters

A novel dual-mode resonator called metal-dielectric coaxial (MDC) resonator for compact inline bandpass filters is proposed. The dual-mode resonator occupies the same size as that of a conventional metallic coaxial resonator but co-supports the TEM and a HE
11
modes. Among various applications of the new dual-mode resonator for inline filters, a possible use in a cascade quadruplet (CQ) section that produces one transmission zero (TZ) on each side of the passband is discussed in detail. To demonstrate the applicability of the MDC dual-mode resonator, a 6-pole inline bandpass filter with an asymmetric response is designed, fabricated, and tuned. Experimental results show that the MDC dual-mode resonator filter can achieve a favorable RF performance while having a compact inline physical structure.