A novel approach to design wideband bandstop filter with wide upper bandpass bandwidth

Abstract

A novel circuit configuration is proposed to design a new wideband bandstop filter with wide upper bandpass bandwidth. This structure includes two coupled-line sections with open-circuit stubs, two transmission-line sections, and a coupled line with an inner connection. This novel bandstop filter can reject relatively wide frequencies (about 55%) with wide upper bandpass bandwidth (about 5.36 times). The measured stopband 15-dB insertion-loss bandwidth is 580 MHz (from 0.79 GHz to 1.37 GHz) at a center frequency of 1.05 GHz (the measured highest rejection is 57.88 dB). The measured 15-dB return-loss lower bandpass band is from DC to 0.4 GHz. In addition, the measured 15-dB return-loss upper bandpass band is from 2.03 GHz to 5.63 GHz, indicating 5.36 times the center frequency. There is a good agreement between the full-wave simulation and measurement.