Antennas

• US 8,680,450 B2
• Filed: 06/11/2010
• Issued: 03/25/2014
• Est. Priority Date: 06/19/2009
• Status: Active Grant

• Current Assignee: MBDA UK Ltd. (MBDA SAS)
• Original Assignee: MBDA UK Ltd. (MBDA SAS)
• Inventors: Pritchard, Timothy John
• Primary Examiner(s): GREGORY, BERNARR E
• Application Number:
  US12/996,915
• Publication Number:
  US 20110215190A1
• Time in Patent Office: 1,383 Days
• Field of Search: 244 31- 319, 343/700.R, 343/705, 343/708, 343711-713, 343/753, 343/756, 343/757, 343/761, 343767-772, 343/776, 343779-781 CA, 343/832, 343835-840, 343/907, 343/909, 343/910, 343912-916, 359/618, 359/629, 359/634, 359/642, 359/726, 359/727, 359/728, 359/729
• US Class Current: 244/3.16
• CPC Class Codes: F41G 7/008 Combinations of different guidance systems
• CPC Class Codes: F41G 7/2246 Active homing systems, i.e. comprising both a transmitter and a receiver
• CPC Class Codes: F41G 7/2253 Passive homing systems, i.e. comprising a receiver and do not requiring an active illumination of the target
• CPC Class Codes: F41G 7/2286 using radio waves
• CPC Class Codes: F41G 7/2293 using electromagnetic waves other than radio waves
• CPC Class Codes: H01Q 1/28 Adaptation for use in or on aircraft, missiles, satellites, or balloons
• CPC Class Codes: H01Q 15/0013 said selective devices working as frequency-selective reflecting surfaces, e.g. FSS, dichroic plates, surfaces being partly transmissive and reflective
• CPC Class Codes: H01Q 15/14 Reflecting surfaces; Equivalent structures electromagnetic shields H01Q1/526
• CPC Class Codes: H01Q 19/062 for focusing
• CPC Class Codes: H01Q 19/19 comprising one main concave reflecting surface associated with an auxiliary reflecting surface
• CPC Class Codes: H01Q 19/195 wherein a reflecting surface acts also as a polarisation filter or a polarising device

Abstract

A reflector 38 includes a mirrored surface 48 and a frequency selective surface 46. The frequency selective surface 46 is arranged to reflect radiation of a first frequency band 52 and allow radiation of a second frequency band 50 to pass. The mirrored surface 48 is arranged to reflect radiation of the second frequency band 50. In this manner, the focal power for radiation of the first frequency band 52 is independent to the focal power for radiation of the second frequency band 50. Accordingly, the design of optical components associated with the second frequency band 50 can be undertaken independently of those associated with the first frequency band 52 so as to achieve the optimised focusing for each frequency band.

Claims

1. A Cassegrain antenna system comprising a primary reflector and a secondary reflector, the secondary reflector comprising:

a mirrored surface;

a frequency selective surface associated with the mirrored surface;

wherein the frequency selective surface is configured to reflect received radiation of a first radio frequency band and allow received radiation of a second frequency band to pass, the second frequency band including the electro-optic range of frequencies;

and wherein the mirrored surface is configured to reflect the received radiation of the second frequency band;

thereby the focal power for received radiation of the first radio frequency band is independent of the focal power for received radiation of the second frequency band.

2. A Cassegrain antenna system, as claimed in claim 1, wherein the mirrored surface is a Mangin mirror configured to aid correction of aberrations associated with the second frequency band.

3. A Cassegrain antenna system, as claimed in claim 1, wherein the secondary reflector further comprises a meniscus lens, the frequency selective surface is mounted on a convex surface of the meniscus lens, the mirrored surface is mounted on a concaved surface of the meniscus lens and the meniscus lens is configured to aid correction of aberrations associated with the second frequency band.

4. A Cassegrain antenna system, as claimed in claim 1, wherein the secondary further comprises:

a meniscus lens having a convex surface and a concaved surface; and

a reflector element,

wherein the frequency selective surface is mounted on the convex surface of the meniscus lens, and the mirrored surface is provided by the reflector element,

and wherein the reflector element forms an air gap with the concaved surface of the meniscus lens and the meniscus lens is configured to aid correction of aberrations associated with the second frequency band.

5. A Cassegrain antenna system, as claimed in claim 1, wherein the frequency selective surface is a dichroic surface.

6. A Cassegrain antenna system, as claimed in claim 1, wherein the frequency selective surface includes an array of tripoles arranged in an equilateral triangular pattern.

7. A Cassegrain antenna system, as claimed in claim 1, wherein the frequency selective surface includes a grid configured to reflect radiation of the first radio frequency band and transmit radiation of the second frequency band.

8. A Cassegrain antenna system, as claimed in claim 1, wherein the second frequency band includes a plurality of sub-bands of frequencies.

9. A missile seeker comprising a Cassegrain antenna system comprising a primary reflector and a secondary reflector, the secondary reflector comprising:

a mirrored surface;

a frequency selective surface associated with the mirrored surface;

wherein the frequency selective surface is configured to reflect received radiation of a first radio frequency band and allow received radiation of a second frequency band to pass, the second frequency band including the electro-optic range of frequencies;

and wherein the mirrored surface is configured to reflect the received radiation of the second frequency band;

thereby the focal power for received radiation of the first radio frequency band is independent of the focal power for received radiation of the second frequency band.