Low cost interference reduction system for GPS receivers

• US 6,590,528 B1
• Filed: 12/05/2001
• Issued: 07/08/2003
• Est. Priority Date: 12/05/2001
• Status: Expired due to Term

• Current Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Original Assignee: Rockwell Collins, Inc. (Raytheon Technologies Corporation d/b/a RTX)
• Inventors: DeWulf, Thomas V.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US10/005,237
• Time in Patent Office: 580 Days
• Field of Search: 342/16, 342/357.06, 342/357.12, 342/378, 342/383
• US Class Current: 342/357.63
• CPC Class Codes: G01S 19/18 Military applications
• 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 19/36 relating to the receiver frond end
• CPC Class Codes: H01Q 13/12 Longitudinally slotted cylinder antennas; Equivalent structures
• CPC Class Codes: H01Q 3/2629 Combination of a main antenna unit with an auxiliary antenna unit
• CPC Class Codes: H04K 2203/32 including a particular configuration of antennas
• CPC Class Codes: H04K 3/228 Elimination in the received signal of jamming or of data corrupted by jamming interference suppression in receivers H04B1/10
• CPC Class Codes: H04K 3/90 related to allowing or preventing navigation or positioning, e.g. GPS

Abstract

A low-cost interference reduction system reduces interfering and jamming signals in a global positioning system receiver for such applications as rotating weapons and hand-held GPS receivers. A pair of antennas having a spin symmetric gain pattern receive global positioning system signals and interfering signals. An antijam electronics function connected to the antennas processes the global positioning system signals and the interfering signals to produce an output signal with reduced interfering signal levels. The global positioning system receiver is connected to the antijam electronics function for processing the global positioning system signals into position solutions and for providing a power detector output and a clock output to the antijam electronics function.

Claims

1. An interference reduction system to reduce interfering signals in a global positioning system receiver comprising:

a pair of antennas having a spin symmetric gain pattern for receiving global positioning system and interfering signals;

an antijam electronics unit connected to the antennas for processing the received global positioning system and interfering signals and producing an output signal with reduced interfering signals; and

the global positioning system receiver connected to the antijam electronics unit for processing the global positioning system signals into position solutions and for providing a power detector output and a clock signal to the antijam electronics unit to reduce the interfering signals.

2. The interference reduction system of claim 1 wherein the pair of antennas comprises a reference antenna and a secondary antenna.

3. The interference reduction system of claim 2 wherein the antijam electronics unit further comprises:

a first amplifier and filter function connected to the reference antenna to filter and amplify the reference antenna received GPS and interfering signals;

a second amplifier and filter function connected to the secondary antenna to filter and amplify the secondary antenna received GPS and interfering signals;

a complex weight circuit connected to the second amplifier and filter function for adjusting the secondary antenna signal phase and gain using in-phase and quadrature gain signals;

a summing function connected to the first amplifier and filter function and the complex weight circuit for adding the reference antenna signal to the adjusted secondary antenna signal to provide a summing function output signal with reduced interfering signals; and

a microprocessor for receiving and measuring the power detector output from the GPS receiver and generating the in-phase and quadrature gain signals for the complex weight circuit.

4. The interference reduction system of claim 3 wherein the antijam electronics unit further comprises:

a digital attenuator connected to the output of the summing function and the microprocessor to vary the level of the summing function output signal to the GPS receiver to maintain a level within range of an AGC circuit in the GPS receiver; and

a digital to analog converter connected to the microprocessor and the complex weight circuit to convert the in-phase and quadrature gain signals from digital to analog.

5. The interference reduction system of claim 1 wherein the GPS receiver further comprises an AGC function for controlling signal levels in the GPS receiver and for providing the power detector output signal.

6. The interference reduction system of claim 5 wherein the GPS receiver further comprises a frequency standard for providing the clock signals to the GPS receiver and the antijam electronics unit.

7. The interference reduction system of claim 1 wherein the antennas are slot antennas.

8. A low cost interference reduction system for a global positioning system receiver comprising:

a reference antenna for receiving global positioning system signals and the interfering signals;

a secondary antenna for receiving global positioning system signals and interfering signals;

a complex weight circuit for adjusting the secondary antenna received signal phase and gain with in-phase and quadrature gain signals;

a summing function for adding the reference antenna received signal to the adjusted secondary antenna received signal to reduce the interfering signals in the summing function output signal;

the global positioning system receiver for processing the received global positioning system signals into position solutions and for providing a power detector output and a clock signal; and

a microprocessor for receiving the power detector output and the clock signal from the GPS receiver and generating the in-phase and quadrature gain signals for the complex weight circuit such that the interfering signals are reduced.

9. The interference reduction system of claim 8 further comprising:

a first amplifier and filter function connected to the reference antenna and the summing function to filter and amplify the GPS and jamming signals; and

a second amplifier and filter function connected to the secondary antenna and the complex weight circuit to filter and amplify the GPS and jamming signals.

10. The interference reduction system of claim 8 further comprising:

a digital attenuator connected to the output of the summing function and the microprocessor to vary the level of the summing function output signal to the GPS receiver to maintain a level within range of an AGC circuit in the GPS receiver; and

a digital to analog converter connected to the microprocessor and the complex weight circuit to convert the in-phase and quadrature gain signals from digital to analog.

11. The interference reduction system of claim 8 wherein the GPS receiver further comprises an AGC function for controlling signal levels in the GPS receiver and for providing the power detector output.

12. The interference reduction system of claim 8 wherein the GPS receiver further comprises a frequency standard for providing the clock signals to the GPS receiver and the microprocessor.

13. The interference reduction system of claim 8 wherein the antennas are slot antennas.

14. The interference reduction system of claim 8 wherein the antennas are circumferential band antennas.

15. The interference reduction system of claim 8 wherein the antennas are dual dipole antennas.

16. A method of reducing the effect of interfering and jamming signals on global positioning system signals in a GPS receiver comprising the steps of:

receiving global positioning system signals and the interfering signals with a reference antenna;

receiving global positioning system signals and interfering signals with a secondary antenna;

adjusting the secondary antenna received signal phase and gain using in-phase and quadrature gain signals in a complex weight circuit;

adding the reference antenna received signal to the adjusted secondary antenna received signal in a summing function to reduce the interfering signals in a summing function output signal;

processing the global positioning system signals into position solutions in the GPS receiver;

providing a power detector output and a clock signal from the GPS receiver;

receiving the power detector output and the clock signal from the GPS receiver in a microprocessor; and

generating the in-phase and quadrature gain signals for the complex weight circuit in the microprocessor such that the interfering signals are reduced.

17. The method of reducing the effect of interfering and jamming signals on global positioning system signals in a GPS receiver of claim 16 further comprising the steps of:

filtering and amplifying the GPS and jamming signals in a first amplifier and filter function connected to the reference antenna and the summing function; and

filtering and amplifying the GPS and jamming signals in a second amplifier and filter function connected to the secondary antenna and the complex weight circuit.

18. The method of reducing the effect of interfering and jamming signals on global positioning system signals in a GPS receiver of claim 16 further comprising the steps of:

varying the level of the summing function output signal to the GPS receiver to maintain a level within range of an AGC circuit in the GPS receiver with a digital attenuator connected to the output of the summing function and the microprocessor; and

converting the in-phase and quadrature gain signals from digital to analog in a digital to analog converter connected to the microprocessor and the complex weight circuit.

19. The method of claim 16 further comprising the steps of:

controlling signal levels in the GPS receiver with an AGC function; and

providing the power detector output from the AGC function in the GPS receiver.

20. The method of claim 16 further comprising the step of providing the clock signals to the GPS receiver and the microprocessor from a frequency standard in the GPS receiver.