Acoustic-wave-lumped-element resonator-based bandpass filters

This chapter has been devoted to the RF design of a new class of planar microwave RF filters in which AW resonators are effectively combined with LEs to create quasielliptic bandpass-type transfer functions with the following unique RF performance characteristics: (i) FBWs that do not depend on the kt2 of the AW resonators, (ii) high Qeffs of the order of a thousand, (iii) passbands whose in-band group delay (Tg) can be designed to be flat, and (iv) transfer functions with multiple levels of continuous analog RF tuning. In particular, we focused on a new RF design approach that uses as a basis CM-based synthesis. The extraction of CM-based models for singleand multimode AW resonators as well as their equivalents when used in series or parallel configurations have been discussed in detail. Using as a basis these CM AWLR-based models, the synthesis and RF circuit/EM design of high-order BPFs has been presented. In particular, we demonstrated quasi-elliptic transfer functions with maximally flat-, equiripple-, and Gaussian-type in-band response. Furthermore, we additionally addressed the realization of multiband bandpass-type transfer functions with symmetric or asymmetric-passbands. RF tuning methods using variable reactive elements have also been discussed and demonstrated the potential for multiple levels of transfer-function tunability including passband bandwidth, out-of-band isolation, and selectivity. Lastly, this chapter presented practical integration schemes using commercially available SAW resonators and LEs.