GB2366913A

GB2366913A - Radar signature reduction

Info

Publication number: GB2366913A
Application number: GB8624292A
Authority: GB
Inventors: John Nicholas Shepherd
Original assignee: British Aerospace PLC; BAE Systems PLC
Current assignee: BAE Systems PLC
Priority date: 1985-10-11
Filing date: 1986-10-09
Publication date: 2002-03-20
Anticipated expiration: 2006-10-09
Also published as: GB8525106D0; FR2867281A1; GB8624292D0; IT8748167A0; GB2366913B

Abstract

Radar signature reduction apparatus for a vehicle (e.g. an aircraft or missile) equipment installation including equipment and a radiation transparent panel behind which the equipment is mounted, the apparatus including means to temporarily place a radar absorption and/or deflection means between the equipment and a remote vehicle detection radar source during periods in which the equipment is non-operating and to temporarily remove the radar absorption and/or deflection means during periods in which the equipment is operating. The radar absorption and/or deflection means may be an inflatable cone 7 of a thin flexible metallised coated material mounted in a radome ahead of the aircraft/missile's radar 2.

Description

<Desc/Clms Page number 1> RADAR SIGNATURE REDUCTION This invention relates to vehicle structures adapted to reduce or at least change the radar signature of the vehicle. By radar signature is meant that characteristic radar signal which, when the vehicle is illuminated by a radar emission, is returned from the vehicle and received back at the radar source.

The term vehicle is to be used in a broad sense to include aircraft and other aerial vehicles, such as guided weapons, additional to ground or sea based vehicles. The term structure is also used in a board sense to include the structure of items carried by the vehicle. In the case of aircraft these items can be for example reconnaissance/surveillance pods and the like.

It can be shown that equipment installations such as radar, laser, or sensing equipment generally and the panels or domes, transparent to the particular radiation associated with the equipment, which the equipment is housed behind, make a significant contribution to the radar signature of a vehicle. This is particularly so if the equipment installation is of the radar type where an enemy search radar operating at the same frequency or at certain multiples of the equipment operating frequency, due to the design and nature of the panel or dome can cause high level returns.

It is an objective of the present invention to so adapt such an equipment installation that its radar signature is reduced when the equipment is not operating, without materially affecting its performance when it is actually operating. Naturally when the equipment is operating it is difficult or impossible to effect

reduction in radar signature and the present invention presently only addresses the non-operating state..

According to one aspect of the present invention an equipment installation including equipment and a radiation transparent panel behind which the equipment is mounted, further includes means to temporarily place a radar absorption and/or deflection means between the equipment and the radar source during the equipment non-operating period and to temporarily remove said radar absorption and/or deflection means during the equipment operating period.

Where there is sufficient clearance between the interior of the panel and the equipment, the radar absorption and/or deflection means may be mounted between the panel and the equipment.

If there is sufficient clearance, when for example, the panel is in the form of a dome (a radome for example) then the radar absorption and/or deflection means can be shaped such that it needs only to provide a deflection function. In this case it may be in the form of a cone.

When fulfilling the deflection function, the radar absorption and/or deflection means may conveniently be formed from a thin flexible film of material with a metallised coating. If of a suitable shape, it can be made expandable; thus the cone previously mentioned may be formed of flexible material which is expanded when its radar deflection shape is required and contracted when it is not required. In the contracted state it provide little or no barrier to the radiation emitted from or received by the equipment when operational.

The expansion may be effected by inflation if the flexible material is in the form of an envelope.

One embodiment of an equipment installation according to the invention is described with reference to the accompanying drawing which illustrates an aircraft nose region.

In the drawing an aircraft has a nose region with a transverse bulkhead 1 on which is mounted radar equipment 2 including a forward looking antenna 3. Forward of the equipment 2 extends a radome 4 which conveniently, but not essentially, carries a pitot tube 5. As is usual practice, the radome extends well forward of the radar equipment to provide an smooth low drag contour for the aircraft; it thus provides an enclosed void region 6 forward of the antenna 3.

To reduce the aircraft's radar signature when the radar equipment is not operating, an inflatable envelope 7 of flexible metallised plastics film is provided in the void region 6. Means to effect this inflation are provided at 8. When inflated the envelope 7 assumes a cone within the void region 6 of an included angle such that any incident enemy search radar signals are deflected away rather than reflected directly back to the search radar source.

When the radar equipment 2 is operating, the envelope 7 is deflated.

Various other arrangements are possible.

For example, in the example illustrated, the cone can be formed again of a flexible thin film material but expanded and contracted by an umbrella-type mechanism.

In other arrangements, not shown, where the absorption function is to be fulfilled, the absorptive layer may be in the form of a roller blind movable across the equipment aperture when necessary. This arrangement has particular use where the void 7 is small, or where the radome is in effect a generally flat panel with only a small clearance between the panel and the antenna.

Claims

CUIMS 1. Radar signature reduction apparatus for a vehicle equipment installation including equipment and a radiation transparent panel behind which the equipment is mounted said apparatus including means to temporarily place a radar absorption and/or deflection means between the equipment and a remote vehicle detection radar source during periods in which the equipment is non-operating and to temporarily remove said radar absorption and/or deflection means during periods in which the equipment is operating.
2. Radar signature reduction apparatus as claimed in claim 1 and wherein the radar absorption and/or deflection means is mounted between the panel and the equipment.
3. Radar signature reduction apparatus as claimed in claim 1 or claim 2 for an equipment installation in which said radiation transparent panel is in the form of a dome e.g. a radome and wherein the radar absorption and/or absorption and/or deflection means is shaped at least during said equipment non-operating periods so as only provide a deflection of signals from said remote radar source.
4. Radar signature reduction apparatus as claimed in any preceding claim and wherein said radar absorption and/or deflection means is formed from a thin flexible film of material with a metallised coating.
5. Radar signature reduction apparatus as claimed in any preceding claim and wherein said radar absorption and/or deflection means is expandable.
6. Radar signature reduction apparatus as claimed in claim 3, 4 or claim 5 and wherein said radar absorption and/or deflection means is in the form of a cone.

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7. Radar signature reduction apparatus as claimed in claim 5 or claim 6 wherein said radar absorption and/or deflection means is expanded when its radar deflection shape is required and contracted so as to provide little or no barrier to radiation emitted from or received by the equipment when it is not required.
8. Radar signature reduction apparatus as claimed in claim 7 and wherein expansion of said radar absorption and/or deflection means is by means of inflation.
9. Radar signature reduction apparatus substantially as hereinbefore described and with reference to the accompanying drawing.

7. Radar signature reduction apparatus as claimed in claim 5 or claim 6 wherein said radar absorption and/or deflection means is expanded when its radar deflection shape is required and contracted so as to provide little or no barrier to radiation emitted from or received by the equipment when it is not required.

8. Radar signature reduction apparatus as claimed in claim 7 and wherein expansion of said radar absorption and/or deflection means is by means of inflation. 9. Radar signature reduction apparatus substantially as hereinbefore described and with reference to the accompanying drawing.

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Amendments to the claims have been filed as follows 1. Radar signature reduction apparatus for a vehicle equipment installation including equipment and a radiation transparent panel behind which the equipment is mounted said apparatus including means to temporarily place a radar absorption and/or deflection means between the equipment and a remote vehicle detection radar source during periods in which the equipment is non-operating and to temporarily remove said radar absorption and/or deflection means during periods in which the equipment is operating. 2. Radar signature reduction apparatus as claimed in claim 1 and wherein the radar absorption and/or deflection means is mounted between the panel and the equipment. 3. Radar signature reduction apparatus as claimed in claim 1 or claim 2 for an equipment installation in which said radiation transparent panel is in the form of a dome e.g. a radome and wherein the radar absorption and/or deflection means is shaped at least during said equipment non-operating periods so as only provide a deflection of signals from said rer;ote radar source. 4. Radar signature reduction apparatus as claimed in any preceding claim and wherein said radar absorption and/or deflection means is forfied from a thin flexible film or material oith a -@tallised coating. 5. Radar signature reduction apparatus as claimed in any preceding claim and wherein said radar absorption and/or deI-lection means is expandable. 6. Radar signature reduction apparatus as claimed in claim 3, 4 or claim 5 and wherein said radar absorption and/or deflection means is in the form of a cone.

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