A wideband bulk acoustic wave filter with modified lattice configuration

This paper proposes a modified lattice configuration of aluminum nitride (AlN) based bulk acoustic wave bandpass filter, which effectively broadens the pass band width without sacrificing the insertion loss and out-of-band rejection. The novel topology comprises two auxiliary inductors paralleled in the balanced input and output of the conventional lattice topology. The performance of the filter is evaluated theoretically as well as experimentally. It is found that, in multistage configuration, the number of auxiliary inductors decreases exponentially, enabling the compact integration of filter chips. This topology is further validated from the experiment, with the filter bandwidth measured to be 400 MHz at central frequency of 3.25 GHz (12.3 % relative bandwidth), which is in excellent agreement with the simulation.