volume | PIER Journals

Abstract

This paper introduces a novel method for designing a wideband tunable bandstop filter (BSF) with constant absolute bandwidth (ABW). The design uses a doublet configuration, where two varactor-tuned resonators are symmetrically coupled to a main transmission line. To maintain constant ABW during frequency tuning, a coupling scheme is proposed where coupling strength decreases as the frequency increases, eliminating the need for additional circuits. Theoretical analysis and closed-form equations are provided for designing the BSF with a wide tuning range. A BSF prototype is designed and tested, demonstrating a 10-dB ABW of approximately 190 MHz across a continuous stopband tuning range from 3.3 to 5.1 GHz, with a fractional tuning range of 42.9%.

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Mr. Qi Zheng

Dr. Pengyu Yu

Prof. Yuhua Cheng

Dr. Pengde Wu