Bleustein-Gulyaev-Shimizu wave resonators formed on ceramic substrates and their applications

In a frequency range that is between 30 and 60 MHz, piezoelectric resonators have not been employed widely in consumer electronics due to their size and the difficulty in precisely tuning their frequencies. Thus, liquid crystal (LC) resonators have been extensively used instead. The authors of this paper have successfully developed and commercialized Bleustein-Gulyaev-Shimizu wave free-edge reflection resonators made of piezoelectric ceramics lead zirconate-titanate (PZT), which have both a small temperature coefficient (9 ppm/°C) and a large electromechanical coupling coefficient (k₂ = 0.22). These resonators have been evaluated as additional traps for nonfrequency tuning resonators that replace both LC resonators requiring tuning and resonators needing autofrequency tuning (AFT). In the former application, the present resonators exhibit trap characteristics with steeper and larger attenuation than those of conventional LC resonators. In the latter application, the present resonators exhibited AFT sensitivity characteristics which are similar to those of conventional LC resonators. When the present resonators were incorporated into voltage-controlled oscillator circuits, they exhibited a very wide adjustable frequency range of 3.7 MHz.