We have developed a low-coherence interferometer system used for the simultaneous measurement of refractive index n and thickness t of transparent plates. Both the phase index n(p) and group index n(g) can be determined automatically in a wide thickness range of from 10 microm to a few millimeters. Two unique techniques are presented to measure n(p), n(g), and t simultaneously. One allows us to determine n(p), n(g), and t accurately by using a special sample holder, in which the measurement accuracy is 0.3% for the thickness t above 0.1 mm. In the other technique the chromatic dispersion delta n of index is approximately expressed as a function of (n(p) - 1) on the basis of measured values of n(p) and n(g) for a variety of materials, and then the simultaneous measurement is performed with a normal sample holder. In addition, a measurement accuracy of less than 1% is achieved even when the sample is as thin as 20 microm. The measurement time is also 3 min or more.

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This paper proposes simple and precise nonlinear simulation techniques for surface acoustic wave (SAW) duplexers, especially for the in-band 3rd order nonlinear distortion, the socalled 'triple beat'. The simulation model is based on the nonlinearity of SAW stress vs. strain (nonlinear elasticity of SAW), and needs just one nonlinear parameter, which represents the 3rd order nonlinear coefficient for the elastic constant. The simulation results of the triple beat for 1.9 GHz Personal Communications Service (PCS) SAW duplexers demonstrate fairly good agreement with the measurements with an accuracy of less than 1 dB.

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