HARMONIC-SUPPRESSING BANDPASS FILTER BASED ON COUPLED TRIANGULAR OPEN-LOOP STEPPED-IMPEDANCE RESONATORS

摘要

This work develops two harmonic-suppressing bandpass filters. One has a direct-coupled-resonator structure and the other has a cross-coupled-resonator structure. The triangular open-loop stepped-impedance resonator is used to synthesize filters because it can create two tunable transmission zeros to suppress multi-spurious responses in the upper stopband. The coupling coefficients of typical coupled pairs of resonators and the external quality factors of two basic feeding configurations are exploited in filter synthesis. A three-pole Chebyshev filter and a four-pole selective-response filter are designed and fabricated herein. The first spurious peaks of these two experimental filters occur at five times and four times the operating frequency, respectively.