Novel compact band‐pass filter with three transmission zeros

Abstract

This article presents a novel compact band‐pass filter (BPF) using two stepped‐impedance resonators. The proposed resonator can work at two modes: quarter‐wavelength resonance mode and half‐wavelength resonance mode. The selectivity of proposed BPF is improved by three transmission zeros (TZs). For these three TZs, one is located at the lower out of band and the other two TZs are placed at the upper out of band. The measured results show that the fabricated filter achieves a pass‐band with insertion losses of 1.02 dB at 4.7 GHz and a stop‐band (both lower and upper) rejection larger than 27 dB. The operating bandwidth is 1.65 GHz and the fractional bandwidth is 30% with a compact size of 23 × 8.5 mm2.