Design of compact microstrip lowpass filters using coupled half-circle defected ground structures (DGSs)

In this paper we have proposed a new half-circle resonators and investigated different coupling effects In order to realize a compact structure. The use of DGS in form of halfcircle shape improves the stop band characteristics. The new DGS-form allows a compact slot with a double coupling, thus a controlled of the resonance pole. The new filter has been designed, fabricated and measured. Good agreement between simulated and measured results has been achieved.