Compact 13–34 GHz ultrawideband on-chip bandpass filter using the coupled meandered line

Abstract

This article presents an ultrawideband (UWB) bandpass filter (BPF) using integrated passive device technology on a GaAs substrate. This bandpass filter uses a multistage coupled line to achieve an ultrawide passband. The filter with a 3 dB fractional bandwidth can achieve a UWB of 106.1% (11.8–38.5 GHz). Introducing short-circuit capacitors and two open microstrip lines between coupling lines achieved two transmission zeros on both sides of the passband and excellent frequency selectivity. Furthermore, to improve impedance matching performance within the ultrawide passband, a step impedance resonator (SIR) structure was adopted for the coupling line. To demonstrate the working mechanism of the proposed BPF, an LC equivalent circuit model was proposed and analyzed to investigate transmission poles and zeros. The suggested filter was fabricated into a small size of 1.4 × 0.85 mm². According to the measurement results, the filter's insertion loss in the 13–34 GHz range was less than 2 dB, and its return loss exceeded −12 dB. The improved performance of the suggested filter was validated by the consistency between simulation results and measured findings.