Accurate solutions of acoustic waves in piezoelectric substrate and metal film as layered structure were obtained. Phase velocity, electromechanical coupling coefficient and static capacitance were calculated based upon the solutions. Chen and Haus＇ theory was used to analyze surface acoustic waves in shorten gratings with single finger every period and a reflection coefficient expression of one strip was presented. Parameters of aluminum on X-112°Y LiTaO3 and gold on ST-quartz were calculated. The results agreed well with those from Ken-ya Hashimoto＇s theory. The reflection coefficient of gold on ST-quartz was measured to verify the theoretical result.
An analysis of the response of surface acoustic wave sensors coated with polymer film based on new coating deposition （self-assemble and molecularly imprinted technology） is described and the response formulas are hence deduced. Using the real part of shear modulus, the polymer can be classified into three types： glassy film, glassy-rubbery film and rubbery film, Experimental results show that the attenuation response is in better consistence with the simulation than in Martin＇s theory, but the velocity response does not accord with the calculation exactly. Maybe it is influenced by the experimental methods and environment. In addition, simulations of gas sorption for polymer films are performed. As for glassy film, the SAW sensor response increases with increasing fihn thickness, and the relationship between the sensor response and the concentration of gas is pretty linear, while as for glassy-rubbery flint and rubbery film, the relationship between the sensor sensitivity anti concentration of gas is very complicated. The ultimately calculated results indicate that the relationship between the sensor response and frequency is not always linear due to the viscoelastic prooerties of the polymer.
The closed-form expressions on strip reflection coefficients of tetragonal 4/mmm, hexagonal 6/mm and trigonal 3m crystal, etc, were derived, which are different from that of cubic m3m crystal published. The reflection coefficients of short-circuited Al grating and groove grating on 112° rotated X-cut Y-propagation LiTaO3 are then given. The reflection property of a short-circuited Al -recessed groove grating on 112°LiTaO3 has been experimentally studied and the condition without internal reflection was achieved. It concludes that the structure of single finger without internal reflection can be realized by the short-circuited Al -recessed groove grating on 112°LiTaO3 and thereafter a pass-band filter with central frequency at 255 MHz, bandwidth about 10 MHz, pass-band ripples less than 0.4 dB was yielded.
