Compact Selective Bandpass Filter With Wide Stopband for TETRA Band Applications

A selective miniaturized bandpass filter with wide stopband for TETRA band applications is presented in this paper. Basic resonator used in the filter construction is an open stub-loaded-short-circuited stepped-impedance resonator, which has the inherent property of having harmonics far from the fundamental mode. The high selectivity of the filter is obtained by virtue of the transmission zeros around the passband. The transmission zeros are generated because of the mixed electric and magnetic coupling between the resonators and the feedline structures. The selective filter has a miniaturized size of 0.078λ
_g
× 0.082λ
_g
with a wide stopband extended up to 4.91 times the operating frequency.for