Improvement of Passband Flatness for a Compact, Narrowband, and Highly Selective TM Dual-Mode Filter

Abstract

This article presents a compact, narrowband and highly selective filter with flattened passband response using TM dual-mode cavities. Indispensable passband flatness as well as very high selectivity was achieved using TM dual-mode resonator filter and equalizer. The design of an eighth-order filter is presented with the experimental results at 10.97 GHz and to satisfy the passband flatness requirements, an external equalizer is devised. Comparisons between the filter and equalized-filter results proves the improvement in the amplitude and group-delay flatness simultaneously in the passband.