A Novel High Common‐Mode Suppression Balanced Bandpass Filter With Elliptical SIW Resonator

ABSTRACT A novel substrate integrated waveguide resonator, specifically an elliptical SIW resonator (ESIWR), is proposed in this research. Due to the incomplete symmetry of ESIWR, compared to circular SIW resonator (CSIWR), the natural resonance frequencies of the first degenerate modes TM C110 and TM S110 are different. Additionally, by incorporating C‐slotlines, the coupling between the two ESIWRs is enhanced. Moreover, transmission zeros are introduced through source‐load coupling to enhance frequency selectivity. Furthermore, the use of meandering technique reduces the resonant frequency and lowers the relative size λ g by 12.1%. The simulation and measurement results are in good agreement, demonstrating the realization of three transmission zeros with out‐of‐band suppression levels of 56.5, 68.1, and 69.3 dB, respectively, indicating excellent out‐of‐band suppression performance. Additionally, the measured minimum common‐mode suppression within the passband exceeds 55.8 dB, metal perturbation columns loading desirable common‐mode suppression. Based on the simulation and measurement results, this novel filter is well‐suited for RF front‐end devices in complex electromagnetic environments.