Interference cancellation system for location and direction finding

• US 9,651,652 B2
• Filed: 02/07/2014
• Issued: 05/16/2017
• Est. Priority Date: 02/07/2013
• Status: Active Grant

• Current Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Original Assignee: L3 Technologies, Inc. (L3Harris Technologies, Inc.)
• Inventors: Kpodzo, Elias Bonaventure, Holland, Robert
• Primary Examiner(s): McGue, Frank J
• Application Number:
  US14/175,840
• Publication Number:
  US 20140218240A1
• Time in Patent Office: 1,194 Days
• Field of Search: 342450
• 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 3/043 Receivers
• CPC Class Codes: G01S 5/0215 Interference

Abstract

Systems and methods for cancelling interference while performing direction/location. A combined signal of interest plus interference signal may be received. A copy or sample of the interference signal may be determined. The interference signal and the combined signal of interest plus interference signal may be converted to the optical domain. The interference signal may be optically phase shifted by −180 degrees, which may result in an optically inverted interference signal. The optically inverted interference signal may be variably optically attenuated and/or variably optically time delayed. As a result, interference cancellation of the interference signal from the combined signal of interest plus interference signal may be achieved, resulting in 50 dB or more of cancellation of the interference signal. Direction and/or location finding techniques can be applied to received signals during and/or after interference cancellation.

Claims

1. A method for determining a position of a device experiencing interference, the method comprising:

receiving a plurality of radio frequency (RF) signals from a plurality of transmitters each located at a known position, wherein each respective RF signal of the plurality of RF signals is transmitted from one of the transmitters, and each respective RF signal comprises a respective RF SOI and a respective instance of at least one RF interfering signal;

determining a sample of the at least one RF interfering signal;

converting each of the plurality of RF signals to a plurality of optical signals, and converting the sample of the at least one RF interfering signal to at least one optical interfering signal;

applying a 180 phase shift to the at least one optical interfering signal;

variably attenuating and variably time delaying the at least one optical interfering signal;

combining an instance of the at least one optical interfering signal with each of the plurality of optical signals after variably attenuating and variably time delaying the at least one optical interfering signal;

converting the plurality of optical signals to a second plurality of RF signals after combining the at least one optical interfering signal with each of the plurality of interfering signals; and

estimating a current position based on the known positions of each of the transmitters and one or more of the relative amplitudes of the second plurality of RF signals, the relative timing differences of the second plurality of RF signals, or the relative phase differences of the second plurality of RF signals.

2. The method as in claim 1, wherein estimating the current position comprises performing trilateration using the second plurality of RF signals.

3. The method as in claim 1, wherein estimating the current position comprises performing triangulation using the second plurality of RF signals.

4. The method as in claim 1, wherein at least one interfering signal comprises a plurality of separate interfering signals.

5. The method as in claim 4, wherein one of the plurality of separate interfering signals is determined based on directly sampling a first interfering signal and another of the plurality of separate interfering signals is determined based on estimating a second interfering signal using a directional antenna.

6. A location determining system comprising:

a radio frequency subsystem configured to;

receive a plurality of radio frequency (RF) signals from a plurality of transmitters each located at a known position, wherein each respective RF signal of the plurality of RF signals is transmitted from one of the transmitters, and each respective RF signal comprises a respective RF SOI and a respective instance of an RF interfering signal,

determining a sample of the RF interfering signal, and

send the RF interfering signal and each of the plurality of RF signals to an optical subsystem;

the optical subsystem configured to;

convert each of the plurality of RF signals to a plurality of optical signals,

convert the sample of the RF interfering signal to an optical interfering signal,

apply a 180 phase shift to the optical interfering signal,

variably attenuate and variably time delay the optical interfering signal,

combine an instance of the optical interfering signal with each of the plurality of optical signals after variably attenuating and variably time delaying the optical interfering signal, and

convert the plurality of optical signals to a second plurality of RF signals after combining the optical interfering signal with each of the plurality of interfering signals; and

a digital subsystem configured to estimate a current position based on the known positions of each of the transmitters and one or more of the relative amplitudes of the second plurality of RF signals, the relative timing differences of the second plurality of RF signals, or the relative phase differences of the second plurality of RF signals.

7. The location determining system as in claim 6, wherein one or more of the plurality of transmitters is located at a respective global positioning system (GPS) satellite.

8. The location determining system as in claim 7, wherein at least one of the plurality of transmitters is located at fixed location that is not a satellite and the RF signal corresponding to the at least one of the plurality of transmitters is used as an error correction signal for correcting a position determination that was based on one or more signals transmitted from GPS satellites.

9. The location determining system as in claim 6, wherein one or more of the plurality of transmitters is located at a cellular base station.

10. The location determining system as in claim 6, wherein the digital system is configured to individually control the attenuation and time delay applied in the optical subsystem for each of the plurality of optical signals.