In this paper,a novel two-order controllable mixed electromagnetic coupling filter based on step impedance resonator is proposed.The designed filter consists of two one-quarter wavelength step impedance resonators,where the electrical coupling and magnetic coupling in the mixed electromagnetic coupling are controlled by the interdigital structure with low impedance and conduction needle of the high impedance part,respectively.Furthermore,two pairs of open stubs are loaded symmetrically on feeding lines to generate additional transmission zeros for better frequency selectivity and wide stopband with high rejection levels.Finally,the prototype filter is successfully designed and fabricated with the proposed method.The realized return loss is greater than 18 dB with insertion loss of 0.6 dB.Its upper stopband is significantly ex-tended to three times of the center frequency with a suppression level larger than 17 dB.
关键词
滤波器/混合电磁耦合/传输零点/宽阻带
Key words
filter/mixed electric and magnetic coupling/transmission zero/wide stopband
维普
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