A Novel Filtering Power Divider with Tunable Center Frequency and Bandwidth Using Three-Line Coupled Structure

Abstract

A tunable filtering power divider (FPD) using a pair of varactor-loaded three-line coupled structure (TLCS) is presented in this paper. The design realizes a third-order filtering power division response with two transmission zeros (TZs) in the upper stopband. The prototype tunable FPD is designed and simulated. The simulated results show that tunable center frequency can be tuned from 0.37 to 0.73 GHz, 3 dB-bandwidth can be tuned from 130 to 225 MHz with good return loss (better than 17 dB) and good in-band isolation (better than 15 dB). Moreover, the proposed filter has a compact size of only <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.08\lambda\mathrm{g}\times 0.18\lambda\mathrm{g}$</tex> .