Towards bulk acoustic wave filters at Ka-band

In this work, a bulk acoustic wave coupled resonator filter design that operates in the Ka-band is presented. The use of high resonance modes enables the use of thick piezoelectric layers which present better quality than the extremely thin layers that would be required using the fundamental mode at high frequencies. The low electro-mechanical coupling intrinsic to high resonance modes has been overcome by means of shunt inductors. Insertion losses better than 3.7 dB and return losses higher than 9 dB have been achieved inside the passband in the frequency range 32.3-32.9 GHz.