GB2054855A

GB2054855A - A signal generator for simulating sonar echoes

Info

Publication number: GB2054855A
Application number: GB8023529A
Authority: GB
Original assignee: Vereinigte Flugtechnische Werke Fokker GmbH
Current assignee: Vereinigte Flugtechnische Werke Fokker GmbH
Priority date: 1979-07-19
Filing date: 1980-07-18
Publication date: 1981-02-18
Also published as: FR2461961B1; DE2929201A1; FR2461961A1; DE2929201C2; GB2054855B; NL8001092A

Abstract

A signal generator for simulating sonar echoes for an underwater sonar system having m channel amplifiers for transmitting the signals produced from sonar echoes by sonar receivers during normal use, the signal generator comprising m programmable individual generators (10m) with n signal outputs each, each output being connected to an associated input of n summing amplifiers (11n) each with m inputs, each channel amplifier of the sonar system being fed by an output of a summing amplifier (11n). The signal generator may be used to teach operating personnel how to use underwater sonar systems. <IMAGE>

Description

SPECIFICATION A signal generator for simulating sonar echoes for an underwater sonar system The invention relates to a signal generator for simulating sonar echoes for an underwater sonar system which has n channel amplifiers for transmitting the signals produced from the sonar echoes by the sonar receivers during normal operation.

Underwater sonar systems are devices operating with acoustic energy and providing (data) about an underwater region. The acoustic energy is transmitted by sonar transmitters and the echoes reflected off the underwater flow or ground or objects are picked up by sonar receivers. After subsequent processing of the signals produced from the sonar echoes by the sonar receivers they are passed to a reproducing device for display of the situation underwater. Underwater sonar systems are therefore particularly suitable for military purposes i.e. for underwater reconnaisance and for introducing certain attach and/or defence measures.

When simulating an underwater sonar system, it is most sensible to leave the actual system unchanged as far as possible and only to simulate the signals which the sonar receivers normally produce from the sonar echoes. However, this is not entirely straight forward because a large number of controllable signal generators is required in order to feed the channel amplifiers, which are connected after the sonar receivers, with signals for simulating the very different sonar echoes.

The invention seeks to provide a signal generator for simulating sonar echoes for an underwater sonar system.

According to the invention there is provided a signal generator for simulating sonar echoes for an underwater sonar system having m channel amplifiers for transmitting the signals produced from the sonar echoes by the sonar receivers during normal operation wherein the signal generator comprises m programmable individual generators m each having n signal outputs which are each connected to an associated input of n summing amplifiers each having m inputs summing amplifiers each feeding the outputs of the channel amplifier.

The signal generator in accordance with the invention is in a position to produce a large number of different signals at relatively low cost based on its construction so that the sooner echoes required for reproducing a wide range of different underwater situations may be simulated. Thus the individual generators may be constructed as sinusoidal generators producing signals of all of the n signal outputs when an associated programme input is controlled. The sinusoidal signals produced may therefore be programmed in their phase positions with respect to each other, in their duration, amplitude and operation point so as to simulate the very different sonar echoes.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which Fig. 1 shows a block circuit diagram of an underwater sonar simulator; Fig. 2 shows a block circuit diagram of the signal generator according to Fig. 1; and Fig. 3 shows an individual generator according to Fig. 2.

As the block circuit diagram according to Fig. 1 shows, the underwater sonar simulator comprises an underwater sonar system 1 and a signal simulator 2. The underwater sonar system 1, a known system may be used for this, comprises transmitter and receiver devices 3, a signal evaluation device 4 and a search and classify display device 5. The underwater sonar system 1 is and functually and reciprocally connected to the signal simulator 2 in order to simulate underwater situations. Thus selected operation instruction control a sonar simulation model 6 provided in the signal simulator 2 and the sonar simulation model 6 in turn controls a signal generator 7, also provided in the signal simulator 2, depending also on other simulation input values. This signal generator 7 is the actual subject of the invention and will be described in greater detail below.

The block circuit diagram according to Fig. 2 shows the signal generator 7 which comprises ten programmable individual generators 10 and fifteen summing amplifiers 11. Each individual generator lOi, 102... 1 Orn has fifteen signal outputs each of which is connected to an associated input of the ten summing amplifiers 11 n which each have ten inputs.Thus the -7 outputs of the individual generators 1 ore are applied to the ten inputs of the summing amplifier 1 1~7 respectively while the outputs 0 of the ten individual generators 10m are each connected to the ten inputs of the summing amplifier 110. In the example shown the number m runs from m = 1 to m = 10 while n runs from n = ~, through n = 0 to n = +7 and thus takes on fifteen values. The outputs of the fifteen summing amplifiers 11 feed fifteen channel amplifiers respectively of an existing sonar system and simulate the signals produced from the sonar echoes by the sonar receivers during normal operation.

As may be gathered from Fig. 2, each individual generator 10, has fifteen outputs to which it passes - as Fig. 3 shows -- sinusoidal signals when it is controlled accordingly. In order to trigger the sinusoidal signals, the individual generators 1 Om are provided with four programmable input stages 12, 13, 14, 1 5. The-input stage 1 2 is used for the purpose of affecting the intensity of the signals. which may be set in the embodiment here in eight stages in accordance with three bits. Thus the distance and the reflection property of an object to be displayed changes and is predetermined depending on the desired simulation.The input stage 13, when controlled, determines the time when the sinusoidal signals are to be used so that the distance of a simulated signal echo may change. In the present embodiment programming with eight bits in accordance with 256 spacing stage is provided. The duration of the triggered sinusoidal signals is determined by the input stage 14 which is also provided, while programming is also possible within eight bits corresponding to 256 stages. The input 1 5 which is also provided finally changes the phase positions of the sinusoidal signals with respect to each other in uniform spacing when it is triggered.It is therefore possible to programme within six bits corresponding to 64 stages so that sonar echoes may be simulated at spacings of 5.63 degrees in the case of all round transmission, i.e. from --1800 to + 1800. In the view according to Fig. 3 it may be seen that the phase positions of the sinusoidal signals produced have constant spacing with respect to each other.

The signal generator 7 in accordance with the invention makes it possible to show ten sonar echoes on the search and classify display device 5. However this is too small for a realistic simulation of underwater situations. In order to increase the sonar echoes which may be displayed, the simulated echo signals are associated with only a fraction of the search and classify device 5, while the rest is supplied with new sonar echoes produced by the signal generator. It has proved advisable to divide up the display of the search and classify device 5 into several strips and to couple this sub-division with changes in range. The following table shows the subdivision selected in the present embodiment of the invention and the echoes which may be displayed thereby.

Maximum individual Range in yards No. of strips Echoes 150 10 100 300 20 200 450 30 300 600 40 400 The signal generator 7 may be used, by corresponding programme control, for displaying realistic underwater situations. Thus the size and structure of simulated objects may be determined by several individual echoes arranged directly adjacent each other. The number of individual echoes depends on the sighting angle at which the object is irradiated from the sonar transmitter in reality and on the discrimination of the echo representation. From this it follows that a simulated target abject should be shown by a point echo for example when the distance is great and by several points when it is at a small distance. A further noise generator is associated with the signal generator 7 in order to simulate noisy sonar echoes as in reality if this should be necessary. These simulations and the sonar echoes required to achieve them may be produced by a corresponding program control of the signal generator 7 while the discrimination angle between two objects actually present in reality is determined by there being a predetermined angle between them so that they are recognised as two separate echoes and are therefore to be simulated. The signal generator in accordance with the invention is therefore in a position to satisfy the numerous requirements by means of appropriate program control and is thus exceptionally well suited to teaching operating personnel how to use underwater sonar systems without actually being on a mission.

Claims

1. A signal generator for simulating sonar echoes for an underwater sonar system having m channel amplifiers for transmitting the signals produced from the sonar echoes by the sonar receivers during normal operation wherein the signal generator comprises m programmable individual generators m each having n signal outputs which are each connected to an associated input of n summing amplifiers each having m inputs summing amplifiers each feeding the outputs of the channel amplifier.

2. A-signal generator according to claim 1 wherein the individual generators produce a sinusoidal signals for all of the n signal outputs when a programmable input stage is controlled accordingly.

3. A signal generator according to claim 1 or 2, wherein each individual generator has a programmable input stage which, when controlled accordingly, determines the time when the signal(s) is (are) produced and thus determines the distance of a sonar echo from the sonar receiver.

4. A signal generator according to claim 3, wherein the amplitude of the sinusoidal signals produced by the individual generators is changeable for the purpose of simulating sonar echoes of different intensity, by controlling a programmable input stage.

5. A signal generator according to any one of claims 2 to 4 wherein the duration of the sinusoidal signals produced by the individual generators may be changed by controlling an input stage for simulating point and/or line echoes.

6. A signal generator according to any one of claims 2 to 5 wherein the phase positions of the sinusoidal signals -- which may be passed to the signal outputs of the individual generators -- may simulate an angle of incidence of a sonar echo by control of a programmable input stage and may be changed with respect to each other with uniform spacing.

7. A signal generator according to any one of claims 2 to 6, wherein the frequency of the sinusoidal signals produced by the individual generators coincides with the frequency of one type of operation of the underwater sonar system.

8. A signal generator according to claim 7, wherein the frequency is 100 KHZ.

9. A signal generator according to claim 8, wherein in order to simulate a mode of operation of 300 KHz correspondingly larger phase shifts may be set between the sinusoidal signals produced, while retaining the frequency 100 KH2.

1 0. A signal generator according to any one of claims 2 to 9 wherein a controllable noise generator is associated with the signal generator for affecting the sinusoidal signals produced in order to simulate noisy sonar echoes in dependence on how the noise generator is controlled.

11. A signal generator for simulating sonar echoes for an underwater sonar system substantially as described herein with reference to the drawings.