A Sonar Time Delay Using Charge-Coupled Devices (CCDs)

The design of a time delay using a CCD as the linear delay element is described. The design objectives were a time delay of 160 ms for frequencies up to 14 kHz, and a dynamic range of 40 dB with a minimum signal to noise ratio of 12 dB. Three different commercial BBD and CCD parts were considered. Among problems addressed are the frequency response and some ways to compensate the severe high frequency attenuation. Harmonic distortion and its complex interaction with the sampling that occurs in the CCD are considered. Quantitative filter requirements for eliminating the harmonics are worked out. Noise problems and temperature effects are also discussed.