LINEAR AND NONLINEAR CHARACTERISTICS AND APPLICATIONS OF SURFACE ACOUSTIC WAVE RESONATORS
Abstract
Surface acoustic wave resonators are potentially useful as narrow-band filters in the VHF and UHF frequency ranges. These devices are particularly attractive because they are compact and may be inexpensively replicated by use of the photolithographic techniques and processes developed for integrated circuits. This work deals with a variety of properties and applications of these devices. In particular, we have considered two applications of a four-port device in conjunction with external circuit elements to provide unusual characteristics. A regenerative active resonator has been developed which exhibits electronically variable Q and tunability. A bandpass filter at 34 MHz has been produced which achieves a loaded Q in excess of 30,000 and a peak-to-background ratio exceeding 50 dB. In addition, the device exhibits in insertion gain of 18 dB. Electronic mode selection has also been observed. Bistability and hysteresis has been demonstrated in a similar device. The device also exhibits a hysteresis in its frequency response. A computer program has been developed to model a rather general SAW device usings Mason equivalent circuits. Additional provision has been made to implement the effects of random variations of the equivalent circuit elements by a Monte-Carlo approach. Of particular interest are random variations of the positions of the electrode edges due to the inherent inaccuracies of photomask generating equipment. In particular, it is found the Q of a two-port resonator is severely affected by these errors. In a typical example, the Q is decreased by 50% at 500 MHz for random variations with a standard deviation of less than 1000 (ANGSTROM). In addition, we have analytically investigated the effect of such random errors on interdigital transducers. Generally, the effect on insertion loss is insignificant, but the depth of response traps and out-of-band responses are significantly deteriorated.
Degree
Ph.D.
Subject Area
Electrical engineering
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