Solidly mounted resonators and filters

Acoustic resonators require material interfaces that confine waves to a finite volume in an efficient manner. Conventionally this is achieved by using air or vacuum interfaces at the electrodes. Another technique is to fabricate the resonator onto a set of quarter wavelength thick layers attached to a substrate to form a solidly mounted resonator (SMR). The SMR concept has been used to fabricate low insertion loss filters for GPS and other applications. Filters for GPS having less than 3 dB insertion loss and 40 dB out-of-band rejection have been demonstrated. These filters are composed of ladder networks with series and shunt resonators.