A Dual-Mode Frequency Reconfigurable Waveguide Filter with a Constant Frequency Spacing between Transmission Zeros

This paper presents a novel frequency reconfigurable dual-mode waveguide filter with elliptic response. The proposed filter maintains a constant absolute bandwidth and a constant rejection bandwidth (frequency spacing between transmission zeros) over the tuning range. Furthermore, the filter can be tuned using a single tuning mechanism. A 4th order prototype filter at 11.5 GHz with 50 MHz bandwidth and 2 symmetric transmission zeros (± 45 MHz) is fabricated and measured. The measured tuning range of the filter is 390 MHz within which the absolute bandwidth variation is within ±1 MHz. In-addition, the measured frequency spacing between the transmission zeros varies well within ±2 MHz over the entire tuning range. The proposed filter promises to be useful for flexible payloads in aerospace applications.