GB1251677A - - Google Patents

Abstract

1,251,677. Correlation techniques. INTERNATIONAL STANDARD ELECTRIC CORP. Nov. 27, 1968, No. 56283/68. Heading G1U. A correlation type pulse signalling system providing an output signal with an impulse autocorrelation function incorporates a signal source generating separately coded signals of pseudorandom noise type, an arrangement for multiplexing a number of such signals having predeterminedly related auto-correlation functions such that when suitably detected an output signal with an impulse auto-correlation function will be derived, and a correlation detector for each signal being coupled to the multiplexing arrangement. A coincidence arrangement coupled to all of the detectors provides a composite output signal which comprises an impulse output at a given time and zero output at all other times within a cycle of generated coded signals. The system, which may be e.g. a radar or communication system, enables transmitted power to be increased while ensuring that an unambiguous correlation signal is still obtained at the output. The code generators 2-2n at the transmitter are synchronized from a clock source 1, which also energizes a sync generator 13. The outputs from all the generators and the sync are multiplexed orthogonally at 3 and transmitted. At the receiver the codes are demultiplexed at 7 and the sync pulses separated at 14 to control the receiver clock 10. Replica codes are generated at 9-9n in sychronism with the clock, and correlated with their respective recovered codes. At least one of the codes provides only a single impulse when correlated with its replica, at a time corresponding to the transmission time, so that the AND gate 12 to which all the correlator outputs are connected will only produce an output impulse at this time. Suitable code combinations for use in the system are indicated in the Specification.