Compact UWB band-pass filter with ring slot resonator structure for improved upper stop-band suppression characteristic

In this paper, a novel ultra-wideband band-pass filter (UWB-BPF) is designed with the ring slot resonator (RSR), which is a hybrid micro-strip and ground slot resonator structure to yield a broad pass-band filtering characteristic. Using the modulated micro-strip stubs and a pair of slits etched on the RSR cell, the poor selectivity and almost no suppression at the upper spurious pass-band ca n be improved effectively. Simulated results are confirmed vi a experiment, showing a good UWB filtering performance with a fractional bandwidth of about 112% from 2.9 to 10.3GHz, a widened upper stop-band up to 20GHz with a rejection level better than 17.6dB, and a sharp skirt at 11.9GHz, simultaneously. In addition, a small area is only about 42.5% of the previous ones.