A Tunable Quarter-Wavelength Coaxial Filter With Constant Absolute Bandwidth Using a Single Tuning Element

This letter presents a novel configuration high-<inline-formula> <tex-math notation="LaTeX">$Q$ </tex-math></inline-formula> coaxial tunable filter that employs a single rotational mechanism to tune the filter while using fixed <inline-formula> <tex-math notation="LaTeX">$\lambda $ </tex-math></inline-formula>/4 resonators. A prototype filter is designed for the proof of concept, which has a tuning range of 11.6% from 685 to 770 MHz, over which bandwidth (BW) variation is within 10.5 MHz ± 0.7 MHz. In addition, the proposed design methodology can be scaled to realize higher order filters. The proposed filter promises to be useful in a wide range of telecommunication applications, including flexible payload in aerospace applications.

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