Compact Microstrip Lowpass Filter with Sharp Roll-off and High Tunability using butterfly-spiral shaped resonator

A novel structure for implementation in the microstrip lowpass filters is presented. The cutoff frequency of the proposed filter is adjusted to 6.42 GHz. The stopband with minimum attenuation level of 20 dB is obtained from 7.06 to 32.18 GHz. The insertion loss from DC to 5.8 GHz is less than 0.2 dB and the return loss is better than 23 dB from DC to 5.64 GHz. The overall size of the proposed filter is only 8.2 mm×5.9 mm. A filter with high return loss, wide stopband and compact size is designed, fabricated and measured, using the proposed resonator. The simulated and measured results are in good agreement.

Keywords:

Insertion loss , microstrip lowpass filter , response tunability , return loss , wide stopband