Low Insertion Loss Bandpass Filter with Controllable Transmission Zeros

• 1、School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510641

Abstract：Planar bandpass filter based on bandstop filter is proposed in this paper. A key merit of the filter configuration is that the position of the transmission zeros can be conveniently controlled whereas the bandwidth is fixed. The bandpass filter is realized using open circuited uniform impedance resonator and stepped impedance resonators. With five reflection zeros generated in the passband, multiple controllable transmission zeros are introduced to sharpen the passband skirt. Skirt selectivity can be freely controlled by tuning the impedance ratio of the stepped impedance resonators. Without coupling gaps between resonators, the new filter shows low insertion loss and is easy for fabrication. To illustrate the concept, a bandpass filter with multiple transmission zeros is designed, fabricated and measured. Simulated and measured results are found to be in good agreement with each other, with insertion loss in the passbands less than 1 dB.

Keywords： electromagnetic field and microwave technology bandpass filter low insertion loss filter transmission zero