Radiation sensor

Details Radiation sensor Radiation sensor

1996-01-19

1998-04-28

Le, Hoanganh T.

Communications: radio wave antennas

Antennas

With spaced or external radio wave refractor

343909, 343911R, H01Q 1906, H01Q 1502

Patent

active

057450820

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention realtes to a radiation sensor, and more particularly, but not execulsively, to such a device for use in radar or communications systems a frequencies in the microwave and millimetre-wave regions of 10 GHz and above.
2. Discussion of Prior Art
Radiation sensors are well known in the prior art. U.S. Pat. No. 4,331,957 describes a dipolar antenna employed in a radar transponder device and used for location of avalanche victims and the like. It is a substantialy omindirectional device, this being a proterty of dipolar antennas, and consequently does not provide directional scene inforamtion. It cannot be used to identify target bearings, and is a short range device (eg 15 meters).
Many radiation sensors are employed as radars, which may be required to provide directional scene information at ranges of the order of kilometers or more. This requires scanning with a directional antenna device such as those employed in the missile seeker field. U.S. Pat. No. 4,199,762 describes a support for a radar antenna, the support being mechanically scanned about two orthogonal axes by virtue of a gimballed mounting. Such a device is compartively bulky and expensive. Moreover, a mechanically scanned antenna is sensitive only to objects within the antenna beam. Fast moving objects passing through the scanned volume need not necessarily encounter the antenna beam.
To overcome the deficiencies of mechanically scanned radars, electronically scanned devices have been developed. Such a device incorporates an array of emitting and/or receiving antennas. The transmit or receive beam direction is controlled by appropriate phasing of the drive signal or local oscillator signal at each antenna. A phased array radar referred to a "MESAR" was disclosed at a conference entitled RADAR 87, London, United Kingdom, 19-21, Oct. 1987. MESAR consisted of an array of 918 waveguide radiating elements arranged in a square of side 2 meters.
Antenna arrays based on dipoles engulfed (ie encapsulated) in dielectric materials are disclosed in U.S. Pat. No. 3,781,896. This disclosure is however silent regarding the formidable design problems involved in feeding signals to and from such an array. It is also silient as regards achieving the required directional properties and measurements.
A further form of radiation sensor is disclosed by Zah et al. in the International Journal of Infrared and Millimeter Waves, Volume 6, No. 10, 1985. It consists of a one-dimensional array of bow tie antennas with integrated diodes arranged in the image plane of a lens system comprising an objective lens and a substrate lens. The signal received by the antennas may be plotted as a function of antenna position to provide an imate. This device has the drawback that it is limited to reception mode operation. Moreover, it only detects radiation having a component polarized parallel to the antennas. There is no transmission capability, nor any provision for detection of other polarizations. A frequent requirement of radar sensors is that they provide for transmission and reception through a single aperture.
Microwave and millimeter-wave staring array technology is described by Alder et al. in the Proceedings of the 20th European Microwave Conference 1990 on pages 454-459. Lens-fed microwave and millimeter-wave receivers with integral antennas as described by Alder et al. on pages 449-453 of the same proceedings.


SUMMARY OF THE INVENTION

It is an object of the invention to provide an alternative form of radiation sensor.
The present invention provides a radiation sensor having radiation guiding means for guiding radiation, the guiding means defining a first plane and a second plane to or from which radiation is to pass, with either receiving means or transmitting means being located in the vicinity of each plane, characterised in that the radiation sensor includes switchable reflecting means for selectably performing the functions of reflecting and transmitting incident radiation.
For the purposes of this

REFERENCES:
patent: 3708796 (1973-01-01), Gilbert
patent: 4447815 (1984-05-01), Ghekroun
patent: 4975712 (1990-12-01), Chen
patent: 5574471 (1996-11-01), Sureau

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