A novel compact UWB bandpass filter with quarter-wave short-circuited stubs

This paper proposed a novel compact ultra-wideband (UWB, 3.1GHz-10.6GHz, defined by U.S. Federal Communications Commission) bandpass microstrip filter with λ₀/4 short-circuited stub to improve the performance and reduce the size of the UWB filter based on the traditional theory. The proposed structure mainly contains two quarter-wave short-circuited stubs and a compact low-pass filter. The measurements show an insertion loss less than 1.8dB and a return loss above 12dB, the rectangular coefficient of the filter also had been improved and the parasitic passband at twice the center frequency had been suppressed. The dimension of this structure is 8.2mm×5.85mm, which is much less than conventional structures.