GB2111785A - Radar source location apparatus - Google Patents

Abstract

An antenna (24) scans in azimuth for radar radiation; when radiation is received the scanning stops. A sighting means (10, 12 (Figure 1, not shown), 11,21) is mounted to point in the same direction as the antenna, so when the antenna stops scanning the sighting means is aligned in azimuth with the radiation source. <IMAGE>

Description

SPECIFICATION Radar warning apparatus This invention relates to radar warning apparatus, particularly for use with helicopters.

One of the major threats to military helicopters are radar-guided weapons, such as guns and missiles. It is possible to equip a helicopter with one or more radar warning receivers, but the problem has been to provide adequate angular coverage whilst at the same time giving a reasonable indication of the direction of the radar source.

It is an object of the present invention to provide radarwarning apparatus which overcomes the above-mentioned problems.

According to the present invention there is provided radar warning apparatus which includes sighting means mounted for movement in azimuth so as to scan an area, an antenna sensitive to radiation of a predetermined frequency mounted on the sighting device and boresighted therewith in azimuth, receiver means connected to the antenna, scanning means operable to cause the sighting means to scan repetitively in azimuth over the said axis, and control means responsive to the detection of radiation by the receiver means to stop the operation of the scanning means in such a position that the sighting means is aligned in azimuth with the source of the radiation.

Many military helicopters are fitted with stabilised optical sighting devices for surveillance purposes.

Frequently these sights combine other functions; for example a laser range-finder may be included, as may a television camera and/or an infra-red sighting device.

The invention will now be described with reference to the accompanying drawings, in which Figure lisa schematic diagram of a stabilised sight carrying and antenna; and Figure 2 is a schematic block diagram of the control means.

Referring nowto Figure 1,this shows the major parts of a conventional stabilised optical sight as used on a helicopter. The gyroscope and inner gimbal are not shown, but the outer gimbal 10 is supported about a vertical axis in a support frame 11. The outer gimbal 10 carries a mirror 12 which is rotatable about a horizontal axis parallel to the axis of the inner gimbal and coupled to it to produce the desired compensating movements. A torque motor 13 is carried on the inner gimbal axis of the gyro. The outer gimbal axis carries a torque motor 14 and a pickoff 15.

The supporting frame 11 is carried on bearings on the body 16 of the helicopter so as to be able to rotate about the axis of a light beam 17 reflected from the mirror 12. The supporting frame is driven through gearing 18 buy a motor 19, having an associated pickoff 20. Carried by and rotatable with the supporting frame 11 is a protective housing 21, having a window 22 through which light may enter to be reflected from the mirror 12.

In order to move the sight in elevation and azimuth to enable an observerto view in any required direction, electrical signals are applied to the azimuth and elevation torque motors on the gyroscope.

Thus an elevation control signal EC is applied to torque motor 14 to cause the mirror 12 to move in elevation. Similarly an azimuth control signal AC is applied to torque motor 13 to cause the outer gimbal 10 to move in azimuth. Such movement is detected by pickoff 15 and drives motor 19 to rotate the supporting frame 11 and protective housing 21 so that the window 22 remains in front of the mirror 12.

The pickoff 20 provides a signal which operates an indicator 23 showing the heading of the sight.

The description given above is that of a known gyroscopically stabilised sight. The protective housing 21 carries a directional radar antenna 24 which is boresighted in azimuth with the sight. The antenna has a beam which is narrow in azimuth and wide in elevation, since its elevation cannot be altered. The antenna is connected to a radar warning receiver (not shown).

Figure 2 shows the control arrangements for the sight and warning device shown above. The gyroscope is shown schematically at 30, with its elevation control input EC. The output from the outer gimbal pickoff controls movement of the supporting frame 11, and housing 21,which is mechanically coupled to the antenna 24. Movement of the gyroscope, and hence of the housing 21 and antenna 24, is controlled either manually or automatically, depending upon an automatic scan control signal ASC, which controls the state of a bistable circuit 30. The absence of the signal sets the bistable circuit 30 to a state in which a gate 31 is enabled to allow the normal azimuth control signal AC to be applied to the gyro 10. When the scan control signal ASC is present, the bistable circuit 30 is set to its other state in which a gate 3 is enabled.The ASC signal also causes a scan generator 33 to function, producing an output via gate 3 to the gyro 10 to cause the sight and antenna to execute a repetitive scanning movement over any desired angle, say 1200 in azimuth.

The radar antenna 24 is connected to a receiver 34 which, on receiving a signal from the antenna, causes the scan generator to stop. The receiver may also provide an audible alarm by way of a transducer 35. When the scan is stopped in this way the sight will be pointing at the source of the radar radiation, and the observer may look through the sight towards the source, though the elevation of the sight may have to be changed. In addition the indication 23 will indicate the bearing of the radar source to the pilot, enabling him to take any appropriate action.

Preferably, the sight will be placed in the cyclic scanning mode when not being used and controlled manually by an observer. The radar warning receiver will provide an audible warning even if the sight is being controlled manually.

The control circuitry described above is intended to be schematic only, and the effect desired may be provided in a number of different ways. The stabilised sight need not take the form described above.

As already stated, the sight may include a laser rangefinder,television and orthermal imaging systems.

Claims (7)

1. Radarwarning apparatus which includes sighting means mounting for movement in azimuth so as to scan an area, an antenna sensitive to radiation of a predetermined frequency mounted on the sighting means and boresighting therewith in azimuth, receiver means connected to the antenna, scanning means operable to cause the sighting means to scan repetitively in azimuth over the said area, and control means responsive to the detection of radiation by the receiver means to stop the operation of scanning means in such a position that the sighting mean is aligned in azimuth with the source of the radiation.

2. Apparatus as claimed in Claim 1 in which the scanning means provides an electrical signal for application to the sighting means.

3. Apparatus as claimed in either Claim 1 or Claim 2 in which the control means is operable to enable the movement of the sighting means to be manually controlled.

4. Apparatus as claimed in any one of Claims 1 to 3 in which the antenna is sensitive to radarfrequen- cies.

5. Apparatus as claimed in any one of the preceding claims in which the receiver means includes means for providing an audible indication of the detection of radiation.

6. Apparatus as claimed in any one of the preceding claims in which the sighting means comprises an optical sight having a protective housing rotatable with the sight and carrying the antenna.

7. Radar warning apparatus substantially as herein described with reference to the accompanying drawings.