AbstractThis letter presents a novel tunable coupling structure to simplify the design complexity of the miniaturized fully tunable filter by using open ring and varactors. Based on the proposed novel tunable coupling structure, a fully tunable bandpass filter is implemented with independently tunable operating frequency and bandwidth. The tunable resonator and tunable coupling structure can be easily combined to improve Out-of-band suppression performance. The design procedure of a fully tunable bandpass filter consists of five tunable cavities and tunable coupling rings is also proposed. A prototype of the proposed fully tunable filter is built to verify the design experimentally. Good agreement between simulated and measured results is obtained.
A UHF THIRD ORDER 5-BIT DIGITAL TUNABLE BANDPASS FILTER BASED ON MIXED COUPLED OPEN RING RESONATORS