New Static External Coupling Structure for K-band Frequency-Tunable Constant-Bandwidth Waveguide Filter with Wide Tuning Range

In this paper, we present a new K-band frequency tunable constant-bandwidth filter with no tunable coupling structures. For the purpose of designing such filter, we have developed novel static coupling structures for TM
₀₁₁
mode cylindrical cavity resonators that can result in a constant bandwidth. For verification, we have designed, fabricated and measured a 2nd-order cavity resonator filter utilizing TM
₀₁₁
mode. The measurement shows that the center frequency can be tuned from 21.5 GHz to 23.3 GHz having the constant bandwidth of 250 MHz.