Compact Wideband Bandpass Filter for TETRA Band Applications

This letter proposes a compact wideband bandpass filter using Short Circuited line Loaded Triangular Stub Resonator (SCLTR). The SCLTR makes the filter compact and simultaneously shifts the harmonics to higher frequencies. Six transmission poles generated by six resonators provide wide passband bandwidth and three Transmission Zeros (TZs) escalate the selectivity of the bandpass filter response. Two transmission zeros are created by virtue of Simultaneous Electric and Magnetic Coupling (SEMC) and one because of source to load cross coupling. The designed and fabricated filter is very compact with a size of 0.127λg × 0.133λg, providing -3 dB fractional bandwidth of 20.5% and wide stopband bandwidth from 0.42 to 1.55 GHz. The experimental results are in compliance with the simulated results, which show that the filter is viable for practical use.