Open AccessTunable balanced bandpass filter with constant absolute bandwidth and high common mode suppression
Author(s) -
Song Kaijun,
Wang Xi,
Fan Maoyu,
Chen Yuxuan,
Patience Shema Richard,
Iman Abdelqani Mohamed,
Fan Yong
Publication year - 2020
Publication title -
iet microwaves, antennas and propagation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.555
H-Index - 69
eISSN - 1751-8733
pISSN - 1751-8725
DOI - 10.1049/iet-map.2019.0389
Subject(s) - band pass filter , resonator , passband , coupling coefficient of resonators , bandwidth (computing) , electronic circuit , materials science , equivalent circuit , optoelectronics , physics , electronic engineering , optics , voltage , telecommunications , computer science , engineering , quantum mechanics
A reconfigurable balanced bandpass filter with constant absolute bandwidth (ABW) and high common‐mode (CM) suppression by using the interdigital coupling compensation circuit structure is presented here. The odd‐ and even‐mode equivalent circuits of the presented balanced bandpass filter are presented and analysed. The differential mode and CM signals are misaligned by the half‐wavelength resonators, which are coupled by interdigital coupling circuit to improve the coupling coefficient and decrease the circuit dimension. Changing the voltage of the four varactors, which are placed at two ends of the half‐wavelength resonators with interdigital coupling circuits, can tune the coupling coefficient and resonant frequency at the same time. A tunable balanced bandpass filter with ABW is designed and realised. The measured results indicate that the differential‐mode tuning centre frequency range extends from 0.97 to 1.72 GHz, the 3 dB ABW is 80 ± 5 MHz, and the CM suppression is >30 dB in the differential‐mode operating passband. Experimental results are in good agreement with the theoretical and simulated ones.