Compact Lowpass Filter with Wide Stopband Using Windmill-Shaped Resonator

Abstract

A novel compact lowpass filter using the windmill-shaped resonator is proposed. The proposed filter has 3-dB cutoff frequency at 4.4GHz and 20dB rejection at 5GHz (the transition band is only 0.6 GHz). The filter has wide stopband with attenuation level better than −20dB from 5 up to 20.9GHz. In this work, we have reached the high and wide rejection in stopband with the compact size as well as good insertion and return loss. Finally, the proposed filter has been fabricated and good agreements between the simulated and measured results are obtained.