Cross-correlator circuit

Details Cross-correlator circuit Cross-correlator circuit

1977-03-15

1978-06-27

Tokar, M.

Electricity: measuring and testing

Electrical speed measuring

Including 'event' sensing means

324 77H, 324 77G, G04F 800

Patent

active

040978010

ABSTRACT:
In a system for measuring the time delay existing between two pattern related random signals of similar but not identical modulated characteristics, utilizing the techniques of cross correlation, two analogue input signals are digitally quantized into binary form according to signal polarity. The first or leading quantized signal is delayed by a series of sequential time intervals or sampling periods to provide a time controlled sequence of delayed leading-signals at equal intervals. These delayed leading-signals are compared by a multiplication technique with the quantized second or lagging-signal, the occurrence when the signals correspond being summed in a series of overflow counters. The rate of filling of the responsive counters is proportional to the respective degree of correspondence and leads to one counter overflowing first, being indicative of the most probable time delay between the two signals. A variable frequency oscillator is used to control the sampling period so that overflow takes place most often in a selected one of the series of counters. To improve the time delay resolution, and to utilize higher frequency components of the signals, once a definite indication of cross correlation is achieved, the sampling period is reduced to a chosen fraction, such as one fifth, and increasing the number of time delay intervals imposed on the leading signal by the corresponding integral multiple, namely five to maintain the overflow in the same selected counter. The two mode operation described permits enhanced precision of time delay determination with economy of components. The readout for the system is derived from the oscillator frequency. The system is suitable for use with an ultrasonic velocity meter for measuring liquid flow in a pipe.

REFERENCES:
patent: 3609683 (1971-09-01), Hoffman
patent: 3906213 (1975-09-01), Meriaux

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