A Novel Compact Low-Loss Closely Spaced Dual-Band Filter for Wireless Communications

This paper presents a novel compact low-loss dual-band bandpass filter. It combines the effect of a combline configuration along with a shorted hairpin resonator configuration loaded with a series resonant circuit. The overall configuration manifests a closely spaced dual-band response with a distinct transmission zero in between without any additional circuitry. The circuit is analytically modeled, simulated, and experimentally validated. The measured insertion losses are 1 dB and 0.73 dB in closely spaced bands with center frequencies 1.3 GHz and 1.96 GHz, respectively. This planar filter finds wide application in miniaturized monolithic integration in wireless communication systems owing to its compact size.