This paper documents the design and characterization of a 54-microsecond(s) , continuously variable, acousto-optic delay line developed for radar testing applications. The operating principles of this new common-path delay line architecture are reviewed, and key component selection issues are discussed. Ultimately, the characteristics of these key components limit the achievable performance of the completed delay line. For example, the laser diode introduces high frequency noise at the output of the delay line. This noise, which is a direct function of the relative intensity 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 design and analysis tool is introduced that predicts delay line performance in terms of bandwidth, insertion loss, and acoustic attenuation for this slow shear, tellurium dioxide (TeO2) based delay line. Experimental results are presented showing 10-MHz operating bandwidth at a 33-MHz center frequency. The 3-dB bandwidth is maintained over delays ranging from 0.75 to 54 microsecond(s) .