Multiple-Transmission Zeros Bandstop Filter Based on SAW Resonators and Lumped Elements

In this paper, a method for the integrated design of multiple-transmission zeros bandstop filter is proposed based on surface-acoustic-wave (SAW) resonators and lumped elements. Firstly, an equivalent circuit model is constructed by extracting parameters of surface acoustic wave resonators. On the basis of the series-coupled bandstop network, the lumped resonant unit and impedance transformer are then combined to be equivalent to the equivalent model of surface acoustic wave resonators. To verify the proposed method, a sixth-order dual-zero bandstop filter based on SAW resonators and lumped elements are designed and fabricated. In the frequency range of 916.3 MHz to 917.2 MHz, the measured
$\vert \boldsymbol{S}_{\mathbf{21}} \vert$
of the stopband reaches -20 dB, while
$\vert \boldsymbol{S}_{\mathbf{11}}\vert$
in the concerned passband is below -22 dB.