Improvement of the frequency response of FBAR filters by using parallel or series connected resonators instead of single resonators

The paper investigates an opportunity for improving the frequency response of FBAR lattice filters by replacing some of the single FBARs with two resonators connected in parallel or in series. The method is applied for the basic lattice filter architecture and its modification with twice lower number of FBARs. The theoretical results presented in the paper allow to estimate the change of the resonance frequencies of resonators, connected in series or in parallel; and to derive the conditions for improving the frequency response of the new circuits. Two different options for circuits with improved frequency responses are considered. The theoretical results are confirmed with computer simulations.