A Modified -0/4 Short-Circuited Stub Bandpass Filter with WLAN Stopband for UWB Applications

This paper proposes a modified short-circuited stub bandpass filter suitable for ultra-wideband applications utilizing low temperature co-fired ceramic (LTCC). By modifying the conventional short-circuited stub bandpass filter structure with lower characteristic impedances for stubs and connecting lines, the number of stubs has been reduced from 5 to 2 stubs on a high dielectric constant substrate (epsiv_r = 40). A wireless local area network (WLAN) stopband in the frequency range of 5.15 to 5.825 GHz has been inserted into the filter characteristic using three short-circuited coupled lines. An insertion loss less than 1.0 dB and return loss better than 10 dB in the pass bands have been measured. A bandwidth ratio of 109.49% has been achieved. The dimension of the filter are 4times8times0.57 mm³.