Compact dual-wideband bandpass filter for wireless applications

In this paper, a compact dual-wideband bandpass filter with two reflection zeros in both passbands and two transmission zeros in the stopband, based on a signal interference technique is presented. The proposed filter is formed by a transmission line connected in parallel with a series connection of transmission lines and a short circuited edge coupled line. A simple lossless transmission line model is used to derive the condition for transmission zeros. To validate the theoretical predictions, a compact dual-wideband bandpass filter has been fabricated to operate at GPS and INSAT Satellite bands. The measured 3 dB passband fractional bandwidths are 82.16% and 41.52%, respectively.