JPH011984A - Cross-correlation calculation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a cross-correlation calculation circuit, and in particular to a passive non-norr receiving device, which extracts a target signal arriving from a certain direction above ambient background noise. This invention relates to a cross-correlation calculation circuit that calculates the cross-correlation of left and right reception beam outputs with the acoustic center axis slightly shifted in order to achieve the desired results.

[Conventional technology]

Conventionally, the cross-correlation calculation circuit in this Hashiba Sig Sonar receiver device integrates the left and right receiving beam outputs with the acoustic center axis slightly shifted by △l in a multiplier 7, as shown in Fig. 2. The cross-correlation between the left and right received beam outputs was obtained by time-integrating the outputs of the left and right receiving beams.

[Problem that the invention seeks to solve]

In the above-described conventional cross-correlation calculation circuit, since the superior output is the cross-correlation function, there is a drawback that the output level fluctuates depending on the nature of the target signals received by the left and right receiving beams. For example, the signals received on the left and right receive beams have little correlation, but the correlation output of the signals received at a high level.

It happens that the correlation is very strong but cannot be distinguished from the correlated output of the received signal at a low level. - membrane pressure;
This is a trap that prevents the correlation output from being influenced by the level of the input signal.

A correlation output, that is, a correlation coefficient, normalized with a certain reference value is used.

Cross-correlation function φxy of two signals x(t), y(t)
tτ) is added as shown in the following equation (1).

φXY(T) =Xtt)'/(t + T) =
, rIA−; 几x(t)y (t +'r )d t・
-...-fl) jl) Cross-correlation function of formula 42. x(t), ylt
) Since the maximum value is taken at τ=0, which is equal to the respective root mean square values, the correlation coefficient φxy(τ) is obtained by normalizing with this value. That is, the following equation (2) is obtained.

Here, φxx and φyy are x(t) and y(t), respectively.
is the autocorrelation function of Equation (2) expresses the cross-correlation function as 2
The correlation between the two signals can be extracted without the correlation output being influenced by the input level as described above. FIG. 3 shows a cross-correlation calculation circuit based on equation (2). In Fig. 3, 1 multiplier 9゜10.11 is x
(t)・y(t+τ), x2(t).

y2ttl is calculated, and the horizontal separators 12, 13, and 14 divide the average value

x2[t) and y2(t) are calculated, and then the multiplier 15
．． The square rooter 16 and the divider 17 process the formula (2) to obtain φxy(τ). The cross-correlation calculation circuit shown in Fig. 3 has the above-mentioned advantages.The circuit configuration is complicated and the scale is large. The disadvantage is that it is difficult to do.

An object of the present invention is to eliminate the above-mentioned drawbacks and to provide a cross-correlation calculation circuit that has a simple circuit configuration and can be easily used in a psonar receiver. Means] The circuit of the present invention multiplies the received signals received by a pair of left and right receiving beams set in each azimuth, integrates the received signals over time, and displays the cross-correlation output of the left and right receiving beams on a display, thereby obtaining the target signal. In the cross-correlation calculation circuit of the Bahnopunner receiver, which detects a horizontal separator, and a 711I calculator that adds the outputs of the left and right sets of received beams.

a second multiplier that squares the output of this adder;
a second integrator that time-integrates the output of the multiplier; and a divider that divides the output of the first horizontal separator by the output of the second integrator.

〔Example〕

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention, in which a first multiplier A is used as a multiplier 1. A horizontal divider 2,710 as a first horizontal divider 3, a second multiplier and a multiplier 4 as C:1'. A horizontal divider 5° as a second integrator and a divider 6 are provided.

Prior to the explanation of the implementation of FIG. 1, the basic features of the present invention will be explained.

The cross-correlation calculation circuit ii of the present invention is not shown in Section 3, but is intended to be similar to the calculation output obtained by the circuit configuration, and to be able to be realized with a simple circuit configuration. As shown in Figure 2, the receiving device receives a receiving beam of 1 degree on the left and right. It can be assumed that the background noise level received by the reception beam has approximately the same value within the reception band.Equation (3) approximately holds true.

・・・・・・(3) Therefore, equation (2) can be approximated as a missing equation (4).

φxy(τ) can also be expressed by first order (5).

...... (5) Equation (4) or (5) means that the root mean square value of one of the two input signals x (t) and y (tl, that is, the autocorrelation function This means that it is possible to equivalently obtain the cross-correlation coefficient rather than normalizing it with
．． The average level of y(t), i.e. (xltl+y
(t) By normalizing the cross-correlation function with the root mean square value of J/2, it is possible to realize equation (4) or (5).

Returning to Figure 1 again, the explanation of the trapping example will be continued.

One set of left and right receive beam outputs x(t), y(l is the first power j
After being multiplied by iL unit 1, it is time-integrated by & divider 2.

This output is φxy(τ) in equation (2), that is, the cross-correlation function. In addition, x (t), y (t), and the adder 3 combine the calculations, and this average value is sent to the multiplier 4.
After being squared by the integrator 5, the time is divided by the integrator 5.

As mentioned above, according to the present invention, (4) or (5)
From the equation, we can calculate the cross-correlation by normalizing the cross-correlation function φxy(τ) with the root mean square value of the force, that is, the autocorrelation function of either of the two input signals x (t), y (t) 1 In the present invention, the average level of the two input signals x it), y (t), i.e. tx
Equations (4) and (5) are realized by normalizing the root mean square of m+y(t))/2 with one straight line.

Multiplier 4 squares the output of adder n and multiplier 3, and divides it into horizontal divider 5.
The output of integrator 5 is (xlt)+yi) )/
The root mean square value of 2 is obtained. This root mean square ° value is (2)
Corresponds to the denominator of the expression, that is, the normalized number.

Next, the divider 6 executes the processing of equations (4) and (5) by dividing the output of the integrator 2 by the output of the horizontal divider 5 and normalizing it, and obtains the desired autocorrelation coefficient. get.

〔Effect of the invention〕

As explained above, the present invention makes it possible to equivalently produce a cross-correlation coefficient with a simple circuit configuration without increasing the scale by normalizing with the root mean square value of the average level of two human input signals. This has the effect that it is possible to obtain a cross-correlation output without being influenced by the two input signal levels.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of an embodiment of the cross-correlation calculation circuit of the present invention, and FIGS. 2 and 3 are block diagrams showing the configuration of a conventional cross-correlation circuit. ...Multiplier, 2...Integrator, 3...
...Adder. 4... Multiplier, 5... Horizontal divider, 6...
...Divider, 7... Multiplier, 8...
・Integrator, 9-11... Multiplier. 12-14... Horizontal divider, 15... Multiplier, 16... Square rooter, 17... Divider. Agent Patent Attorney Susumu Uchihara 1 --- * Zu Masumaya 1 Kacha 2 Closed

Claims (1)

[Claims] A passive sonar receiving device that detects a target signal by multiplying the received signal by a pair of left and right receiving beams set in each direction, then integrating it over time, and displaying the cross-correlation output of the left and right receiving beams on a display. In the cross-correlation calculation circuit, a first multiplier that multiplies the outputs of a pair of left and right received beams set in each direction, a first integrator that integrates the output of this first multiplier over time, and an adder that adds a set of received beam outputs, a second multiplier that squares the output of the adder, a second integrator that integrates the output of the second multiplier over time, and the first integrator. a divider for dividing the output of the second integrator by the output of the second integrator, and a cross-correlation coefficient of the left and right received beam outputs is determined as the output of the divider. Arithmetic circuit.