GB1432588A - Circuit arrangement for processing and/or amplifying electrical message signals - Google Patents

Abstract

1432588 Correlators NORMA MESSTECHNIK GmbH 5 June 1973 [16 June 1972] 26693/73 Heading G4A A function of an input signal is derived by using the signal as one of the parameters involved in the formation of a correlation function of an auxiliarly signal. The cross-correlation function of two time-dependent signals e 1 , e 2 is defined as and the auto-correlation function of a single signal e is given by putting e = e 1 = e 2 . The parameter t 1 is an arbitrary time delay. Figs. 1, 2; 3, 4; 8, 9 (taken in pairs) indicate the auto-correlation functions k of various kinds of auxiliary functions S of periodicity 2T 1 and it will be noted that the functions k are periodic. Fig. 10 shows one of a number of similar arrangements for forming the correlation function k using an auxiliarly signal (s) source 1, A/D converters 3a, 3b in respective parallel channels, a delay device 5 (which may be a shift register) in one channel, a correlation function generator 6 (which may be an AND gate) and, optionally, a D/A converter 7. The variation of the correlation signal with the various formation parameters A, T and t 1 are apparent from Figs. 1-9 and the invention consists essentially in varying one or more of these in accordance with an input signal u. Thus, Fig. 2 shows that variation of the delay t 1 in accordance with u such that t 1 < T 1 results in linear amplification of u. Amplification with inversion may be obtained by varying t 1 about a mean value t 1 = 1À5T, within the linear range (Fig. 3, not shown). If t 1 is varied about the value t 1 = T 1 , full wave rectification is obtained as shown in Fig. 4 and half-wave rectification may be obtained by modifying the auxiliary signal s as shown in Fig. 5 and varying t 1 about a value t 1 = (2n-1)T 1 (see Fig. 6). If the auxiliary signal is sinusoidal, the correlation function is a sinusoidal function of t 1 and, for small signals, a variable amplication factor may be obtained to realize dynamic range compression or expansion. The correlation characteristic (Fig. 9) of a sawtooth auxiliary signal (Fig. 8) may be used for measuring the r.m.s. values of periodic signals of indeterminate shape. In the above application where t 1 is the varied parameter, the input may be applied as a variation of the frequency of a clock 4 controlling one of the A/D converters which, in this case, are ergodic converters. The output of the ergodic converter 3b will be time-delayed in accordance with variations in the clock frequency. Otherwise, the input signal is applied to the shift register 5 or to both the clock and the register to obtain similar results. It is stated that the above operations may be performed in a hybrid circuit in which the A/D converter is omitted so that an analogue signal is fed to the device 6 which is, in this case, a multiplier (not fully described). The Specification also describes the use of a stochastic signal to form the autocorrelation function.