Research And Design Of The Microwave Balancedbandpass Filter

With the advent of the 5G era,the transmission rate of information and data in communication system has been greatly increased,and electromagnetic interference between different device modules will occur,thereby the user experience will be affected.The balanced filter not only has frequency selectivity,but also suppresses noise and electromagnetic crosstalk in the environment,so the signal integrity will be ensured.The main contents are as follows:1.An ultra-wideband balanced band-pass filter based on a microstrip/slot line transition structure is proposed.The balanced filter has good differential mode transmission characteristics,the center frequency is about 2.33 GHz,and maximum insertion loss does not exceed-0.6d B,relative bandwidth is up to 118%.These realize ultra wideband characteristics.It has the characteristics of full-band common-mode suppression when common-mode signal excitated.The designed broadband balanced filter is fabricated and measured,the measured results are in good agreement with simulated results.2.A dual-band balanced band-pass filter is proposed.The differential ports are fed by a stepped impedance microstrip/slot line transition structure.The slot line uniform impedance resonator constitutes a dual passband,and the resonator is folded to achieve a compact size,only about 23 mm × 38 mm × 1.016 mm,the inner and outer nested uniform impedance resonators produce two operating frequency points at 1.5 GHz and 2.55 GHz,and the T-slot line branches are loaded to enhance the coupling to improve the performance.The balanced filter has better differential mode transmission characteristics,and realizes common mode suppression in the entire frequency band.By processing and testing,the rationality of the design is further verified.3.A balanced broadband filter based on parallel coupling line is proposed,which adopts the method of combining stepped impedance parallel coupling line and uniform impedance coupling line.The passband selectivity is good,the relative bandwidth of the differential mode is 32%,the maximum insertion loss does not exceed-1.8d B,and the band-stop filtering characteristic is exhibited during the common mode excitation,the operating frequency band is 2GHz to 2.5GHz,which suppresses the common mode signal.The designed broadband balanced filter is fabricated and measured,the measured results are in good agreement with simulated results.