Usually the amplitude of the electrical signal fed to an acousto-optic cell is kept low so that the acousto-optic diffraction becomes approximately linear with respect to the input amplitude. In this paper the approach of describing functions is used to analyze and quantify the nonlinear dependence of acousto-optic diffraction on the input signal amplitude. As a case study the performance of digital filter realizations using acousto-optic cells is analyzed. Acousto-optic digital filters can be used for real time processing of discrete time signals with high sampling rates ( 106per sec). The advantages of the acousto-optics based realization are high throughput rate, high speed and compact size. These filters can be used in adaptive or non-adaptive signal processing applications in the areas such as radar signal processing and video communication systems. Analytical results are obtained using the describing function approach to study the effects of nonlinearity in the acousto-optic Bragg diffraction on the frequency and steady-state responses of both finite and infinite impulse-response digital filters.
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