Design and realization of three-pole bandpass filter with spurious response suppression using defected ground structures

In this paper, a three-pole bandpass filter (BPF) using a new defected ground structure (DGS) is discussed. The proposed DGS is incorporated in the ground plane under the feed lines and the coupled lines of a bandpass filter to improve the performance of the filter in both passband and stopband. The banpass filter is designed with a center frequency of 1.8 GHz and a bandwidth of 270 MHz. The suppression of better than 20 dB was achieved for frequencies between 2.2 and 5 GHz. A prototype of BPF was fabricated and tested. Prototype measured data was in good agreement with simulation results.