A compact microstrip lowpass filter using spiral resonant structure

In this paper, a novel low-pass filter using spiral compact microstrip resonant structure for size reduction and broad pass-band is presented. The proposed low-pass filter is designed, fabricated and tested. The insertion loss of the filter is less than 0.1 dB in the frequency range from DC to 3.5 GHz. The novel low-pass filter has the advantages of low insertion loss in the pass-band, high and wide rejection in the stop-band and compact size. The performances of the proposed filter are demonstrated by measured results, which are good agreement with the simulation ones.