Dual near-field focused antenna array

• US 6,121,933 A
• Filed: 05/24/1999
• Issued: 09/19/2000
• Est. Priority Date: 12/13/1995
• Status: Expired due to Fees

• Current Assignee: Harris Corporation (L3Harris Technologies, Inc.)
• Original Assignee: AIL Systems, Inc. (ITT, Inc.)
• Inventors: Kane, Michael, Silvern, Robert, Cosenza, John M.
• Primary Examiner(s): PHAN, THO GIA
• Application Number:
  US09/317,226
• Time in Patent Office: 484 Days
• Field of Search: 343/700 MS, 343/777, 343/778, 343/795, 343/813, 343/814, 343/840, 343/850, 343/853
• US Class Current: 343/700.0MS
• CPC Class Codes: H01Q 1/38 formed by a conductive layer on an insulating support patch antennas H01Q9/0407; microstrip dipole antennas H01Q9/065; microstrip slot antennas H01Q13/106; transmission line microstrip antennas H01Q13/206; manufacturing reflecting surfaces using insulating material for supporting the reflecting surface H01Q15/142
• CPC Class Codes: H01Q 13/203 Leaky coaxial lines
• CPC Class Codes: H01Q 21/08 the units being spaced along or adjacent to a rectilinear path waveguide fed H01Q21/0037
• CPC Class Codes: H01Q 21/12 Parallel arrangements of substantially straight elongated conductive units travelling-wave antennas comprising transmission line loaded with transverse elements H01Q11/02; Yagi antennas H01Q19/30
• CPC Class Codes: H01Q 3/30 varying the relative phase between the radiating elements of an array H01Q3/2605, H01Q3/2658, H01Q3/2682, H01Q3/44 take precedence
• CPC Class Codes: H04B 7/10 Polarisation diversity; Directional diversity

Abstract

A communication system for transferring data through the air over a relatively short fixed distance comprising a transmitting antenna which comprises a leaky coaxial cable for radiating electromagnetic energy modulated with data to be transferred; and a plurality of non-linear fixed beam array antennas for receiving the modulated electromagnetic energy from the leaky coaxial cable. The plurality of fixed beam array antennas are juxtaposed with the transmitting antenna such that the transmitting antenna extends at least partially through the near-field regions of the plurality of fixed beam array antennas. The communication system also comprises a selection means which determines which radio frequency output from the plurality of non-linear fixed beam array antennas exhibits the greatest radio frequency power and outputs that particular radio frequency output to a receiver. Also described is a method of increasing the performance of an antenna system, which comprises the steps of inputting radio frequency signals from a plurality of antennas, selecting that radio frequency signal which comprises the greatest radio frequency power, and outputting the radio frequency signal comprising the greatest radio frequency power.

Claims

1. An antenna system comprising:

a plurality of antennas, each of said plurality of antennas outputting a radio frequency signal, each of said radio frequency signals having a power associated therewith, each of said plurality of antennas receiving said radio frequency signal from a source, said source being located in a near field region of at least one of said plurality of antennas, said source being located a variable distance from at least one of said plurality of antennas;

a detection circuit, the detection circuit being responsive to said radio frequency signals output from said plurality of antennas, said detection circuit outputting a control signal, said control signal being representative of which of said radio frequency signals has a greatest power; and

an output circuit, said output circuit being responsive to said control signal, said output circuit outputting said radio frequency signal having said greatest power in response to said control signal, thereby increasing an immunity to said variable distance between said source and said at least one of said plurality of antennas.

2. An antenna system as defined by claim 1, wherein said plurality of antennas includes a plurality of non-linear fixed beam array antennas which receive an electromagnetic beam from said near field region, each of said non-linear fixed beam array antennas comprising:

four conductive patch elements including two inner patch elements and two outer patch elements juxtaposed linearly on a substantially flat substrate, each of said patch elements being arranged to transduce electromagnetic energy into corresponding electrical signals having a phase;

a phase shifter which shifts said phase of said electrical signals from each of said two inner patch elements by an amount substantially equivalent to a difference in time between said electromagnetic beam being incident upon each inner patch element and said electromagnetic beam being incident upon each outer patch element, said phase shifter outputting phase-shifted electrical signals; and

a power divider which coherently adds said phase-shifted electrical signals from each inner patch element and said electrical signals from each outer patch element.

3. An antenna system as defined by claim 1, wherein said detection circuit comprises:

an amplitude comparator which compares amplitudes of each radio frequency signal and outputs said control signal indicative of that radio frequency signal having a greatest amplitude; and

a switch which selects that radio frequency signal having the greatest amplitude in response to said control signal and outputs said radio frequency signal having the greatest amplitude, thereby outputting said radio frequency signal comprising the greatest power.

4. An antenna system as defined by claim 3, wherein said amplitude comparator includes a video detector which determines said amplitude of said radio frequency signals.

5. An antenna system as defined by claim 1, wherein said source includes a transmitting antenna which radiates electromagnetic energy modulated with data to be received by said plurality of antennas.

6. An antenna system as defined by claim 5, wherein said transmitting antenna includes a leaky coaxial cable.

7. An antenna system as defined by claim 6, wherein said leaky coaxial cable and at least one of said plurality of antennas have longitudinal axes, said longitudinal axes being perpendicularly oriented.

8. An antenna system as defined by claim 6, wherein said leaky coaxial cable and at least one of said plurality of antennas have longitudinal axes, said longitudinal axes being oriented in parallel.

9. An antenna system as defined by claim 6, wherein said leaky coaxial cable and at least one of said plurality of antennas have longitudinal axes, said longitudinal axes being positioned at a predetermined angle.

10. A method of increasing performance of an antenna system, which comprises the steps of:

receiving a radio frequency signal by a plurality of antennas, said radio frequency signal being received from a source, said source being located in a near field region of at least one of said plurality of antennas, said source being located a variable distance from at least one of said plurality of antennas;

outputting said radio frequency signals from said plurality of antennas, each of said radio frequency signals having a power associated therewith;

selecting said radio frequency signal output from said plurality of antennas having a greatest power;

generating a control signal, said control signal being representative of said radio frequency signal having said greatest power; and

outputting said radio frequency signal having said greatest power in response to said control signal, thereby increasing an immunity to said variable distance between said source and said at least one of said plurality of antennas and increasing said performance of said antenna system.

11. A method as defined by claim 10, wherein said step of outputting said radio frequency signals further comprises the steps of:

positioning a plurality of fixed beam array antennas, said fixed beam array antennas including four conductive patch elements, said conductive patch elements including two inner patch elements and two outer patch elements arranged in a linear fashion for transducing electromagnetic energy into corresponding electrical signals having a phase and an amplitude and receiving an electromagnetic beam emanating from said near field region;

focusing said plurality of fixed beam array antennas at a focal point located in said near field region;

shifting said phase of said electrical signals from each of said two inner patch elements by an amount substantially equivalent to a difference in time between said electromagnetic beam being incident upon each inner patch element and said electromagnetic beam being incident upon each outer patch element; and

adding said phase shifted electrical signals from each inner patch element and said electrical signals from each outer patch element coherently.

12. A method as defined by claim 10, wherein said step of selecting said radio frequency signals having the greatest power further comprises the steps of:

comparing amplitudes of each radio frequency signal;

outputting said control signal indicative of said radio frequency signal having a greatest amplitude;

switching said radio frequency signal having the greatest amplitude in response to said control signal; and

outputting said radio frequency signal having the greatest amplitude, thereby outputting said radio frequency signal having the greatest power.

13. A method as defined by claim 12, wherein said step of comparing amplitudes further includes the step of amplifying said radio frequency signals.

14. A method as defined by claim 10, further comprising the step of transmitting the radio frequency signals from said source.

15. A method as defined by claim 14, wherein said step of transmitting further comprises the step of radiating electromagnetic energy from a leaky coaxial cable modulated with data.

16. A method as defined by claim 15, wherein said step of transmitting further comprises the step of orienting a longitudinal axis of said leaky coaxial cable perpendicularly to a longitudinal axis of at least one of said plurality of antennas.

17. A method as defined by claim 15, wherein said step of transmitting further comprises the step of orienting a longitudinal axis of said leaky coaxial cable parallel to a longitudinal axis of at least one of said plurality of antennas.

18. A method as defined by claim 15, wherein said step of transmitting further comprises the step of orienting a longitudinal axis of said leaky coaxial cable at a predetermined angle with respect to a longitudinal axis of at least one of said plurality of antennas.

19. A communication system for transferring data comprising:

a transmitting antenna, the transmitting antenna including a leaky coaxial cable, the leaky coaxial cable radiating electromagnetic energy modulated with said data to be transferred;

a plurality of non-linear fixed beam array antennas, said plurality of non-linear fixed beam array antennas receiving said electromagnetic energy modulated with said data, said plurality of non-linear fixed beam array antennas outputting a plurality of radio frequency signals, said plurality of radio frequency signals being representative of said electromagnetic energy modulated with said data, said non-linear fixed beam array antennas being juxtaposed with said transmitting antenna such that said transmitting antenna extends at least partially through a near field region of at least one of said plurality of non-linear fixed beam array antennas; and

a selection circuit, said selection circuit determining which one of said plurality of radio frequency signals has each corresponding to one of said plurality of non-linear fixed beam array antennas, said selection circuit outputting said radio frequency signal having the greatest power.

20. A communication system as defined by claim 19, wherein said transmitting antenna and at least one of said plurality of non-linear fixed beam array antennas have longitudinal axes which are positioned perpendicularly with respect to each other.

21. A communication system as defined by claim 19, wherein said transmitting antenna and at least one of said plurality of non-linear fixed beam array antennas have longitudinal axes which are positioned in parallel with respect to each other.

22. A communication system as defined by claim 19, wherein said transmitting antenna and at least one of said plurality of non-linear fixed beam array antennas have longitudinal axes which are positioned at a predetermined angle with respect to each other.

23. A communication system as defined by claim 19, wherein said selection circuit selects that radio frequency signal having a greatest amplitude and outputs said radio frequency signal having the greatest amplitude, thereby outputting said radio frequency signal having the greatest power.