Radar or sonar detection system

Claim 1

In a radar or sonar system, a combination comprising a transmitter including an encoder for modulating a carrier prior to transmitting the same into the system with a cyclic pulse code sequence which is cycled through a predetermined number of bit positions at a frequency equal to the pulse repetition frequency, and a receiver including a 1-bit analog-to-digital converter comprising a zero-crossing detector for digitizing incoming signals received from respective range cells of the system in response to the effect of the modulated carrier thereat, and a plurality of 1-bit correlators each respectively supplied with the instantaneous value of the digitized signal from said 1-bit analog to digital converter and with the value of the bit of the code sequence then encountered at a predetermined one of said bit positions which is different for each of said correlators and corresponds to the respective range cell, wherein each 1-bit correlator comprises an exclusive-OR gate, said correlators being collectively operative for simultaneously correlating each successive bit of the digitized signal with the values of the respective bits in each expected position of the received code sequence, and a plurality of accumulators, each accumulator comprising an up-down counter connected to an output of one of said respective 1-bit correlators to accumulate the output thereof for a predetermined number of RF pulses.