GPS antenna array and system for adaptively suppressing multiple interfering signals in azimuth and elevation

• US 20100207811A1
• Filed: 02/18/2009
• Published: 08/19/2010
• Est. Priority Date: 02/18/2009
• Status: Active Grant

• Current Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Lackey, Raymond J.
• Granted Patent: US 8,049,667 B2
• Time in Patent Office: Days
• US Class Current: 342/357.440
• CPC Class Codes: G01S 19/21 Interference related issues ; Issues related to cross-correlation, spoofing or other methods of denial of service
• CPC Class Codes: G01S 19/35 Constructional details or hardware or software details of the signal processing chain
• 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 21/293 one unit or more being an array of identical aerial elements adaptive arrays H01Q3/2605
• CPC Class Codes: H01Q 25/00 Antennas or antenna systems providing at least two radiating patterns arrangements for changing or varying the orientation or the shape of the directional pattern H01Q3/00
• CPC Class Codes: H01Q 3/2617 Array of identical elements
• CPC Class Codes: H01Q 9/16 with feed intermediate between the extremities of the antenna, e.g. centre-fed dipole H01Q9/44 takes precedence
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface
• CPC Class Codes: H01Q 9/42 with folded element, the folded parts being spaced apart a small fraction of the operating wavelength

Abstract

An antenna system has N antenna units stacked on a mast. Each unit has elements for responding to, e.g., GPS signals, and a phasing network that produces mutually orthogonal primary and auxiliary pattern modes at corresponding mode ports of the unit. A number of power dividers are each associated with a different mode, and each divider has N input ports coupled to the associated mode port of a corresponding antenna unit. The power divider associated with the primary pattern mode produces a reference beam and an auxiliary beam, and remaining power dividers produce different auxiliary beams. All beams have approximately both a common phase center and a common group delay center. An adaptive processor combines the reference and selected auxiliary beams to obtain a composite antenna reception pattern in which nulls are inserted at certain angles to suppress interfering signals, without degrading authentic signals arriving at other angles.

Claims

1. An antenna system, comprising:

a mast having an axis and arranged to be fixed at a certain position with respect to a surrounding ground area, and to extend vertically above the ground area;

a number (N) of antenna units fixed along the length of the mast with a determined spacing from one another;

each antenna unit includes a number of antenna elements disposed about the periphery of the unit for responding to radio frequency (RF) signals within a certain wavelength band, and an associated phasing network coupled to the elements, wherein the phasing network is configured to produce a number (M) of mutually orthogonal pattern modes including a primary pattern mode at a primary mode port of the associated antenna unit, and one or more auxiliary pattern modes at corresponding auxiliary mode ports of the associated antenna unit;

a number of power dividers each associated with a different mode port of the antenna units, wherein each power divider has N input ports each of which is coupled to the associated mode port of a different antenna unit;

the power divider coupled to the primary mode ports of the antenna units is configured to produce at least a reference beam at a reference port of the divider, and, optionally, an auxiliary beam at an auxiliary port of the divider, and the power dividers coupled to the auxiliary mode ports of the antenna units are configured to produce corresponding auxiliary beams at corresponding auxiliary ports of the dividers; and

an adaptive processor coupled to the reference and the auxiliary ports of the power dividers, and configured to process the reference beam and selected ones of the auxiliary beams to obtain a desired reception pattern for the antenna system.

2. An antenna system according to claim 1, wherein the antenna units are each constructed and arranged substantially identical with one another, so that the reference and the auxiliary beams have approximately both a common phase center and a common group delay center.

3. An antenna system according to claim 1, wherein one or more of the auxiliary beams produced at the auxiliary ports of the power dividers have a carrier phase progression in azimuth that is different from that of the reference beam.

4. An antenna system according to claim 1, wherein the adaptive processor is configured to process the reference and the auxiliary beams from the power dividers to produce one or more nulls in the reception pattern of the antenna system at determined angles in azimuth and in elevation.

5. An antenna system according to claim 4, wherein the adaptive processor is configured to combine the reference and the auxiliary beams subtractively to produce the nulls in the reception pattern.

6. An antenna system according to claim 4, wherein the adaptive processor is constructed and arranged to (i) detect interfering signals arriving at the antenna system at different angles in azimuth and in elevation, and (ii) produce corresponding nulls in the reception pattern of the antenna system to suppress the interfering signals.

7. An antenna system according to claim 1, wherein the antenna elements of the antenna units are configured to respond to RF signals transmitted at a wavelength corresponding to signals used for global positioning or navigation.

8. An antenna system according to claim 7, wherein the signals are transmitted from GPS satellites.

9. An antenna system according to claim 1, wherein each of the antenna units has four or more antenna elements.

10. An antenna system according to claim 1, wherein the antenna elements of the antenna units comprise dipoles.

11. An antenna system according to claim 1, wherein the orthogonal pattern modes produced by the phasing network of each antenna unit are among those of a group comprising a progressive phase omni-directional (PPO) pattern, a uniform phase omnidirectional (UPO) pattern, and a clover leaf pattern.

12. An antenna system according to claim 1, wherein each of the antenna units has eight antenna elements, and the orthogonal pattern modes produced by the phasing network of each antenna unit are among those of a group comprising a 45 degree PPO pattern, a 90 degree PPO, pattern, a 135 degree PPO pattern, a UPO pattern, and a clover leaf pattern.

13. A differential global positioning system (DGPS) including at least one antenna system according to claim 1, a GPS receiver coupled to the antenna system, a processing system coupled to the receiver and operative to compare a global position calculated by the receiver with a known reference position and to produce a resulting error signal, and a transmission system coupled to the processing system for transmitting the error signal to an aircraft for landing approach guidance.

14. A DGPS according to claim 13, wherein the surrounding ground area at which the mast structure of the antenna system is arranged to be fixed is in the vicinity of a ground airport runway.

15. A DGPS according to claim 13, wherein the surrounding ground area at which the mast structure of the antenna system is arranged to be fixed is in the vicinity of a landing zone on an aircraft carrier.

16. A collinear antenna array, comprising:

a mast having an axis and arranged to be fixed at a certain position with respect to a surrounding ground area, and to extend vertically above the ground area;

a number (N) of antenna units fixed along the length of the mast with a determined spacing from one another; and

each antenna unit includes a number of antenna elements disposed about the periphery of the unit for responding to radio frequency (RF) signals within a certain wavelength band, and an associated phasing network coupled to the elements, wherein the phasing network is configured to produce a number (M) of mutually orthogonal pattern modes including a primary pattern mode at a primary mode port of the associated antenna unit, and one or more auxiliary pattern modes at corresponding auxiliary mode ports of the associated antenna unit.

17. An antenna array according to claim 16, wherein N is at least three.

18. An antenna array according to claim 16, wherein M is at least three.

19. An antenna array according to claim 16, wherein one or more of the auxiliary pattern modes produced at the auxiliary mode ports of the antenna units have a carrier phase progression in azimuth that is different from that of the primary pattern mode.

20. An antenna array according to claim 16, wherein the antenna elements of the antenna units are configured to respond to RF signals transmitted at a wavelength corresponding to signals used for global positioning or navigation.

21. An antenna array according to claim 16, wherein each antenna unit has four or more identical antenna elements selected from the group comprising dipoles and monopoles, the antenna elements are disposed symmetrically about the periphery of each unit, and the antenna elements of a given unit align with the antenna elements of a next adjacent unit on the mast in the direction of the mast axis.

22. An antenna system according to claim 16, wherein the antenna units are each constructed and arranged substantially identical with one another, so that the primary and the auxiliary pattern modes have approximately both a common phase center and a common group delay center.