A Microstrip Wideband Balun Bandpass Filter with H-shape Resonators

Abstract

A novel approach to design a Microstrip wide band bandpass filter (BPF) with H-shaped resonators is exhibited in this letter. By using the standing-wave property of voltage conveyance along an open circuited half-wavelength (λ/2) Microstrip transmission line, the out-of-phase signs can be acquired at two yield ports of a balun. In the mean time, appropriate coupling topologies between the open-circuited λ/2 Microstrip transmission line and the multi-mode resonators are designated to accomplish a balun BPF with both attributes of parity balance performance and wideband filtering properties. To validate proposed work, a balun BPF working at 1 GHz with a 3 dB FBW of 30% is simulated and measured. Both the simulation and measurement results of the composed balun BPF with H-shaped resonators are given a decent assertion. Results demonstrate that this balun BPF displays not just a high selectivity filtering execution with two regular transmission zeros (Tzs) of S21 and S31 outside the passbands, additionally a decent adjust execution with 0.5 dB amplitude imbalance and 5° phase imbalance.