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A bstruet-A new acoustooptic architecture for performing real-time correlation of tigh-frequency wide-band signals has beerr developed. It uses a surface-acoustic-wave (SAW) delay line, and features the optical interference of two coherent light beams which have been Bra&-diffracted by SAW's propagating in the tine. The signal muttipiication, and subsequent time integration of the product formed, is performed by a photodiode array which deteets the diffracted tight. This arehitectrrre has achieved tirstebandwidths products exceeding 106 (34 MHz X 30 ins), and has several attributes which make it particularly well suited for use as a spread-spectrum signal processor. These include linearity of operation, large dynamic range, a large time aperture over which the correlation can be observed, and the ability to determine the center frequency and bandwidth of the signals. A correlator with this architecture has been used to detect a number of wide-band spread-spectrum signals. Its suitability for nse as a signal processor in several spread-spectrum systems is considered. I. INTRODUCTION EVERAL present-day radio systems munications, navigation, and radar used for commake use of spread-spectrum techniques to obtain greater range, multi-Manuscript

A new realization of the acousto-optic time-integrating correlator has been constructed. The new device uses a surface-acoustic-wave delay line and is configured so that no separate reference beam is required for coherent detection. Instantaneous bandwidths of 30 MHz and integration times of 30 ms have been achieved. Broadband signals, such as pseudonoise biphase modulated waveforms, with signal-to-noise ratios of −40 dB have been detected. In addition, center frequency, bandwidth, and relative time-difference-of-arrival of these signals can be determined.

A new architecture for performing time -integration correlation is described.The correlator uses a surface acoustic wave (SAW) delay line, and features the optical interference of two coherent light beams which have been Bragg-diffracted by SAW's propagating in the line. The time integration is performed by a photodiode array which detects the diffracted light. Time-bandwidth products exceeding 106 (50 MHz times 30 ms) have been achieved. This two -beam SAW acousto -optic time -integrating correlator has been used to detect a number of wideband spread-spectrum signals.It has several attributes which make it particularly well suited for use as a spread-spectrum signal processor.These include linearity of operation, large time aperture over which the correlation can be observed, and the ability to determine the center frequency and bandwidth of the signals.The suitability of this correlator for use as a signal processor in spread-spectrum systems is considered.In addition, a two -dimensional realization of this correlator is proposed for frequency scanning correlation.The use of this frequency scanning correlator as an LPI radar signal processor is discussed.I. AbstractA new architecture for performing time-integration correlation is described. The correlator uses a surface acoustic wave (SAW) delay line, and features the optical interference of two coherent light beams which have been Bragg-diffracted by SAW's propagating in the line. The time integration is performed by a photodiode array which detects the diffracted light. Time-bandwidth products exceeding 10" (50 MHz times 30 ms) have been achieved. This two-beam SAW acousto-optic time-integrating correlator has been used to detect a number of wideband spread-spectrum signals. It has several attributes which make it particularly well suited for use as a spread-spectrum signal processor. These include linearity of operation, large time aperture over which the correlation can be observed, and the ability to determine the center frequency and bandwidth of the signals. The suitability of this correlator for use as a signal processor in spread-spectrum systems is considered. In addition, a two-dimensional realization of this correlator is proposed for frequency scanning correlation. The use of this frequency scanning correlator as an LPI radar signal processor is discussed.

A novel structure for a coherent-interferometric acousto-optic (AO) time-integrating correlator has been implemented by using a single surface acoustic wave (SAW) device with tilted transducers to reduce intermodulation terms. 175 MHz, a bandwidth of 60 MHz, and a time aperture of about 10 ps. The instantaneous bandwidth of the A0 correlator is determined by the spacing density of the photodetector array, with a potential of 120 MHz. Typical integration times are 30 to 40 ms, providing processing gains in excess of l o 6 , Such a device is very useful in providing fast synchronization of communication links. In addition, the device can demodulate to base band and simultaneously act as a synchronization lock monitor for moderate data rates. Where processing may be limited by doppler shifts, a two-dimensional architecture has been imgl.emented to allow full processing gain e