Compact wide stopband lowpass filter using spiral loaded tapered compact microstrip resonator cell

Abstract

A new spiral loaded tapered compact microstrip resonator cell (SPLT-CMRC) is presented. The addition of spiral stubs to the CMRC creates transmission zeroes in the stopband which extended the stopband of the filter. The proposed resonator is used to design a compact lowpass filter (LPF) with wide and high rejection in stopband. The fabricated filter has a 3 dB cutoff frequency at 8 GHz. The insertion loss in the passband is less than 0.2 dB from DC to 7.2 GHz. The proposed filter has wide stopband from 9.47 to 40 GHz with attenuation level of −20 dB. The demonstrated filter is designed and fabricated. There is a good agreement between the measured and simulated S-parameters.

Keywords:

• Microstrip lowpass filter
• resonator cell
• wide stopband