COMPACT DUAL-BAND BANDPASS FILTERS BASED ON A NOVEL DEFECTED GROUND SPIRAL RESONATOR

A novel defected ground structure spiral resonator with two spiral stubs and a center stub was presented in this article. Full-wave simulation was used to investigate the working principle of the resonator. The results show that the spiral resonator has two operating modes, so that it can produce two resonant frequencies. It is also found that it is convenient to control the two resonant frequencies by adjusting the dimensions of the two spiral stubs and the center stub. A dual-band bandpass filter (BPF) was designed using two resonators of this type and a T-shaped coupling node, having a bandwidth of 4.5% at 1.87 GHz and a bandwidth of 3.3% at 2.43 GHz. The measured results of the designed dual-band BPF agree well with the simulated responses. (c) 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:1636-1640, 2015