DESIGN AND CHARACTERIZATION OF A LONG-TIME APERTURE ACOUSTOOPTIC DELAY-LINE

The design and characterization of a 54-mu s, continuously variable, a cousto-optic delay line developed for radar testing applications is do cumented. The operating principles of this new common-path delay line architecture are reviewed, and key component selection issues are disc ussed. Ultimately, the characteristics of these key components limit t he achievable performance of the completed delay line. For example, th e laser diode introduces high-frequency noise at the output of the del ay line. This noise, which is a direct function of the relative intens ity noise of the laser, is the limit to the output noise floor. Bragg cell design is presented with emphasis on the minimization of multiple time-delayed signals caused by acoustic reflections. A computer desig n and analysis tool is introduced that predicts delay line performance in terms of bandwidth, insertion loss, and acoustic attenuation for t his slow shear, tellurium dioxide (TeO2) based delay line. Experimenta l results are presented showing 10-MHz operating bandwidth at a 33-MHz center frequency. The 3-dB bandwidth is maintained over delays rangin g from 0.75 to 54 mu s.