A compact lowpass filter with ultra-wide stopband using novel resonance cell

Abstract

A novel compact microstrip resonant cell (CMRC) with wide stopband characteristics to design a low pass filter with wide stopband and high rejection is presented. The designed lowpass filter is implemented by cascading two cells with different dimensions. Compared with a conventional CMRC, this work shows the advantages of smaller size, only 7.3*3.7mm2, and high rejection as well as wider stopband. Measured results of the fabricated prototype show that the insertion loss is less than 1 dB in the whole passband, stopband bandwidth better than -20 dB is obtained from 5.7 to 33 GHz and better than -10 dB is obtained from 5.1 to 40 GHz, which is an great improvement of 154.8% from a conventional CMRC.