High-Rejection Compact Wideband Bandpass Filter Based on Bent Coupled Lines

Abstract

A simple planar structure with high stopband rejection for bandpass filter (BPF) is proposed in this paper. The circuit structure consists of three groups of coupled lines (CLs), two short-circuit stubs (SCSs), and stepped-impedance stubs (SISs) to achieve high selectivity of six transmission poles (TPs) and four transmission zeros (TZs). For demonstration, a design prototype working at 2.32 GHz, with 3-dB fractional bandwidth (FBW) of 74.1% is simulated, manufactured, and measured. Moreover, the size of the prototype is successfully reduced using the proposed layout method with the performance not deteriorating. The simulation results are in good agreement with the measured results.