Antenna system for polarization diversity

Patent metadata

Field	Value
Publication number	US-9618606-B2
Application number	US-201415124885-A
Country	US
Kind code	B2
Filing date	Mar 12, 2014
Priority date	Mar 12, 2014
Publication date	Apr 11, 2017
Grant date	Apr 11, 2017

Abstract

An antenna system ( 100 ) comprising a single antenna element having first ( 111 ) and second ( 112 ) antenna ports arranged to pass a respective first and second antenna signal. The first and second antenna signals being derived from a first common antenna signal (J 1 ) and arranged to be essentially equal in envelope. An antenna pattern of the system being arranged to be selectable between a first antenna pattern having a first polarization and a second antenna pattern having a second polarization substantially orthogonal to the first polarization. The first antenna pattern being selected by setting the first and second antenna signal to have the same polarity on first ( 111 ) and second ( 112 ) antenna ports, the second antenna pattern being selected by setting the first and second antenna signal to have substantially opposite polarities on first ( 111 ) and second ( 112 ) antenna ports.

First claim

The invention claimed is:

1. An antenna system ( 100 ) comprising an antenna structure ( 110 ) consisting of a single antenna element having first ( 111 ) and second ( 112 ) antenna ports arranged to pass a respective first and second antenna signal, the first and second antenna signals arranged to be derived from a first common antenna signal (J 1 ) and arranged to be essentially equal in envelope, the antenna structure ( 110 ) being arranged to have an antenna pattern which is selectable between a first antenna pattern having a first polarization and a second antenna pattern having a second polarization substantially orthogonal to the first polarization, the first antenna pattern being selected by setting the first and second antenna signal to have the same polarity on first ( 111 ) and second ( 112 ) antenna ports, the second antenna pattern being selected by setting the first and second antenna signal to have substantially opposite polarities on first ( 111 ) and second ( 112 ) antenna ports.

2. The antenna system ( 100 ) according to claim 1 arranged in either of a receiver mode, a transmitter mode, or a transceiver mode, the antenna structure ( 110 ) when in receiver mode being arranged to output antenna signals on first ( 111 ) and second ( 112 ) antenna ports received via the antenna structure ( 110 ), the antenna structure ( 110 ) when in transmitter mode being arranged to receive antenna signals on first ( 111 ) and second ( 112 ) antenna ports to be emitted via the antenna structure ( 120 ), the antenna structure ( 110 ) when in transceiver mode being arranged to simultaneously output and receive antenna signals on first ( 111 ) and second ( 112 ) antenna ports.

3. The antenna system ( 200 ) according to claim 1 , further comprising a first antenna interface unit ( 210 ) comprising a 180 degree hybrid coupler ( 220 ), a switching unit ( 230 ), and a first common port ( 213 ) for passing the first common antenna signal (J 1 ), the 180 degree hybrid coupler ( 220 ) having first ( 211 ) and second ( 212 ) coupler ports connected to the first ( 111 ) and to the second ( 112 ) antenna port, respectively, as well as a summation ( 221 ) and a difference ( 222 ) port connected to the switching unit ( 230 ), the switching unit ( 230 ) being arranged to connect the first common port ( 213 ) of the antenna interface unit ( 210 ) to either of the summation port ( 221 ) or the difference port ( 222 ) of the 180 degree hybrid coupler ( 220 ), thus selecting between the first and the second antenna pattern of the antenna system ( 200 ).

4. The antenna system ( 250 ) according to claim 1 , the first ( 111 ) and second ( 112 ) antenna ports further being arranged to pass a third and a fourth antenna signal, respectively, the third and fourth antenna signals having substantially identical envelopes and are derived from a second common antenna signal (J 2 ) substantially orthogonal to the first common antenna signal (J 1 ), the antenna system ( 250 ) further comprising a second antenna interface unit ( 260 ), the second antenna interface unit ( 260 ) comprising second ( 261 ) and third ( 262 ) common ports for passing the first (J 1 ) and the second (J 2 ) common antenna signal, respectively, as well as a 180 degree hybrid coupler ( 220 ), the 180 degree hybrid coupler ( 220 ) having first ( 211 ) and second ( 212 ) coupler ports connected to the first ( 111 ) and to the second ( 112 ) antenna port, respectively, as well as a summation ( 221 ) and a difference ( 222 ) port connected to the second ( 261 ) and third ( 262 ) common ports, respectively, thus selecting the first polarization for one of the first (J 1 ) and the second (J 2 ) common signal, and selecting the second polarization for the other of the first (J 1 ) and second (J 2 ) common signal.

5. The antenna system ( 250 ) according to claim 4 , wherein the first (J 1 ) and the second (J 2 ) common signal are orthogonal by separation in frequency.

6. The antenna system ( 250 ) according to claim 4 , wherein the first (J 1 ) and the second (J 2 ) common signal are orthogonal by separation in time.

7. The antenna system ( 250 ) according to claim 4 , wherein the first (J 1 ) and the second (J 2 ) common signal are orthogonal by separation in code.

8. The antenna system ( 300 ) according to claim 1 , the antenna structure ( 110 ′) comprising an elongated conductive bridge ( 310 ) having a length (L H ) between first and second ends smaller than half of the wavelength corresponding to the highest frequency of the first common antenna signal (J 1 ), the antenna structure ( 110 ′) further comprising two elongated conductive legs arranged in parallel and having respective lengths (L V1 , L V2 ) between first and second ends smaller than half of the wavelength corresponding to the highest frequency of the first common antenna signal (J 1 ), said legs ( 320 ) being attached at first leg ends to either end of the elongated conductive bridge ( 310 ) in right angles with respect to the conductive bridge ( 310 ), thus substantially forming a U-shape, the sum of lengths of the elongated conductive bridge ( 310 ) and the two elongated conductive legs ( 320 ) being substantially equal to half of the wavelength corresponding to the center frequency of the first common antenna signal (J 1 ), the first ( 111 ) antenna port being connected to the second end of one leg, the second ( 112 ) antenna port being connected to the second end of the other leg, the antenna structure ( 110 ′) being arranged to have a ground plane ( 330 ) orthogonal to both legs and located approximately at the second ends of the legs, the antenna structure ( 110 ′) having a total length (L TOT ), including elongated conductive bridge ( 310 ) and both legs ( 320 ), less than the wavelength corresponding to the highest frequency of the first common antenna signal (J 1 ).

9. The antenna system ( 400 ) according to claim 8 , wherein the elongated conductive bridge ( 310 ) is extended by first ( 410 ) and second ( 420 ) conductive extension units connected at either end of the elongated conductive bridge ( 310 ), thus substantially forming a H-shape, the total length of the elongated conductive bridge with extension units ( 410 , 420 ) being smaller than the wavelength corresponding to the highest frequency of the common antenna signal (J).

10. The antenna system ( 100 , 200 , 300 ) according to claim 1 , wherein the length of the elongated bridge is approximately 1.2 meters, and the length of both legs is approximately 1 meter.

11. The antenna system ( 100 , 200 , 300 ) according to claim 1 , wherein the length of one of the legs is approximately 0 meters, thus substantially forming a single leg antenna system.

12. The antenna system ( 100 , 200 , 400 ) according to claim 9 , wherein the length of the elongated conductive bridge ( 310 ) with extension units ( 410 , 420 ) is approximately 3 meters, and the length of each leg is approximately 1.2 meters.

13. The antenna system ( 100 , 200 , 300 , 400 ) according to claim 1 , wherein the antenna system is configured to be mounted on an airborne vehicle ( 710 , 810 ).

14. The antenna system according to claim 13 , wherein the airborne vehicle ( 710 , 810 ) is a ground plane of the antenna system ( 100 , 200 , 300 , 400 ).

15. The antenna system ( 100 , 200 , 300 , 400 ) according to claim 13 , wherein the antenna system is configured to be mounted on an airborne vehicle ( 810 ) comprising first and second landing skids ( 820 ), and wherein the antenna system is positioned between the first and second landing skids ( 820 ).

16. The antenna system ( 100 , 200 ,

Assignees

• Saab Ab

Inventors

• Hellsten Hans

Classifications

• H04B7/10

  Polarisation diversity; Directional diversity · CPC title

• H01Q11/14

  with parts bent, folded, shaped or screened or with phasing impedances, to obtain desired phase relation of radiation from selected sections of the antenna or to obtain desired polarisation effect (H01Q11/20 takes precedence) · CPC title

• H01Q7/00

  Loop antennas with a substantially uniform current distribution around the loop and having a directional radiation pattern in a plane perpendicular to the plane of the loop · CPC title

• H01Q1/28 Primary

  Adaptation for use in or on aircraft, missiles, satellites, or balloons · CPC title

• G01S13/885 Primary

  for ground probing (prospecting or detecting using electromagnetic waves G01V3/12) · CPC title