The Monolithic FM Discriminator A New Piezoelectric Device

The concept of controlled acoustic coupling between thickness shear trapped energy resonators fabricated on a single quartz plate led to the development of the monolithic crystal filter. Recent work at the Bell Telephone Laboratories has resulted in the development of a three-port monolithic structure capable of providing the frequency-selective network required for an FM discriminator. This device is capable of providing good linearity over bandwidths ranging from about 0.005 percent to nearly 0.2 percent at center frequencies in the range from 5 MHz to 40 MHz. An analysis of the equivalent network is given, as well as the design procedure. Experimental results from a model having a 15MHz center frequency and 6-kHz linear bandwidth are discussed.