Analog-digital correlator

An analog-digital correlator 10 utilizes a plurality of sample and hold cirucits 16-0 to 16-(M-1) to directly store samples of a received analog signal. Bits of a correlation pattern are shifted through stages in a correlation pattern shift register 26. The state of the correlation pattern bits causes the value in the associated sample and hold circuit 16 to either be inverted or noninverted when it is summed with other similarly generated signals from the remaining sample and hold circuits to form the correlation output sum by network 30. The output of network 30 will peak when the bits of the digital correlation pattern signal are shifted to stages in register 26 that are aligned with the sample and hold circuits containing the digitally-impressed code of interest. In the preferred embodiment, a mask shift register 28 is used to selectively disable certain of the sample and hold circuits from affecting the correlation output sum. To this end, mask bits corresponding to the length of the digitally-impressed code are shifted through mask register 28 simultaneously with the correlation pattern bits in register 26.