GB1161998A - Improvements in Analyzers for Stochastic Phenomena, in particular Correlation Function Computers - Google Patents

Abstract

1,161,998. Correlation calculators; function generators. COMMISSARIAT A L'ENERGIE ATOMIQUE. 27 Oct., 1966 [28 Oct., 1965], No. 48312/66. Headings G4A and G4G. A computer for generating correlation functions of two variables X(t), Y(t) works in real time to avoid the necessity of using a buffer memory of great capacity at the input. Two analogue signals representing the two variables, are applied to analogue to digital converters Ca, Cb which deliver quantized amplitude levels of - 4, - 3 . . . 2, 3, 4, according to the state of their inputs, to delay units Da, Db. The converters Ca, Cb are triggered at equal intervals " h " by clock pulses so that the outputs of Da represent successive samples of X(t) which are entered into 4 bit memory units Q of a memory Ma and sequentially shifted down until the first sample X occupies unit Q 1 , X2 occupies Q 2 &c. up to X 128 which occupies the 128th unit Q 128 . At the instant at which the last sample X 128 is taken, a gate G is opened to allow a corresponding Y(t) sample Y 128 to be applied to a multiplier P. The values X are then taken from memory Ma and the products X 128 Y 128 , X 127 Y 128 ... X 1 Y 128 formed, the values X being returned to memory Ma with unit Q 128 empty, unit Q 127 containing X 128 , unit Q 126 containing X 127 ... unit Q, containing X 2 , X 1 being lost. The outputs of multiplier P are successively applied via adder A to 26 bit memory units R 0 -R 127 of a second memory Mb so that R 0 records product X 128 Y 128 representing a sampling time difference of zero time units, R 1 records product X 127 Y 127 representing a sampling time of " L " time units &c. The outputs of units R 0 -R 127 are connected to a printing device (not shown). Two further sampled values X 129 , Y 129 are now accepted, X 129 entering vacant memory unit Q 128 and Y 129 being applied as before to multiplier P. The products X 129 Y 129 , X 128 Y 129 &c. are formed as above, the values X being again returned to memory Ma as above so that value X 2 is lost. The product X 129 Y 129 representing zero sampling time difference is added to the contents of memory unit R 0 , the product X 128 Y 129 added to R 1 &c. and the complete process then repeated for further value X 130 Y 130 . After sufficient sampling (dependant on error requirements), the correlation functions C xy (h) given by may be obtained from the memory units Ri. The computer may be arranged to accept digital inputs e.g. perforated strips, magnetic strips &c., and the delay elements Da Db may be changed to vary the increment " h " in the functions C xy (h). For high speed sampling the two memories Ma, Mb may comprise two sections of a single thin film magnetic memory. With slight modification the computer may be used to determine the functions: - probability density function of the first order - mean value of a signal - conditional probability density function for two variables - distribution of the delays between correlated aleatory events with an automatic compensation of the background noise. The computer may also act as: - a function generator - a Fourier analyser - an analogue/digital memory for storing and delivering a physical phenomenon represented by a voltage varying as a function of time (or any other parameter).