GB1424535A - Signal correlators - Google Patents

Abstract

1424535 Signal correlators IMPERIAL CHEMICAL INDUSTRIES Ltd 16 April 1973 [28 April 1972] 19785/72 Heading H3H Apparatus is provided for determining an interval of transposition with respect to a parameter of a first signal with respect to a second signal which interval produces the best match between the signals, and employs a first store which is in the form of a shift register for storing a succession of values of samples of the first signal and means for multiplying each value or a sub-set of values by a value of the second signal which is coincident with, or separated by a constant interval of the parameter from the last value fed into the store, and a second store and means for adding the multiples to values held in corresponding locations in the second store to produce running totals in each of these locations, and a comparator to determine the location of the highest value stored in the second store. In the embodiment shown the parameter is time, and two spaced transducers 1, 2 are provided for measuring, e.g. sonic waves in a fluid in a pipe-line. Each signal is converted to a 2-bit binary word at 3, 4 and the output at 3 is taken to 100-stage shift register 5, that from 4 being taken to the inputs of a two-stage flip-flop store 10. A clock source 8 provides pulses at each of which the shift register 5 takes in a new value from the converter 3 and the store 10 is updated from converter 4. Each clock pulse also starts a cycle of address unit 7 which causes sequential read-out of the values in each stage of register 5 by means 6 between each pulse emitted from the source 8. Thus by means of multipler 9, the sample held at 10 of the second signal is multiplied with the present and 99 preceding values of the first signal. Each of these multiples is applied in turn to an adder 12 for addition to a value stored in a corresponding location in a second 100 position store 13, and the sum is replaced for this former value in the same location and is also applied to a comparator 16. If this value is greater than a value stored at 17, this is read into the store 17 and the location address is stored at 18, and transferred to a buffer store 19. After, e.g. 1024 clock pulses as determined by counter 21, the measurement is stopped and the address value stored at 19 is transferred to display 20 where, e.g. the velocity of fluid flow may be read-out directly.