Design of a band-selective filter for UWB applications and its characteristic when combined with band-notched antennas

Abstract

A compact microstrip band-selective filter for ultra-wideband (3.1-10.6 GHz) radio system is proposed. The filter combines an optimum pseudo-bandpass filter and a coupled resonator bandstop filter on both sides of the meandered 50-Omega microstrip line. Three coupled resonators are modified to have S-shape to miniaturize the filter. The measured results show that the filter has wide passband of 146.7% (2.1-10.15 GHz) with low insertion loss and the stop-band of 7.42% (5.29-5.85 GHz) for 3-dB bandwidth. The measured group delay variation is less than 0.7 ns within the passband except the stop band. Finally, the filter is combined with band-notched antennas and then received power levels of the antennas with and without the filter are also examined at the notch frequency.