Interference cancellation system for cancelling interference in the optical domain

• US 9,748,987 B2
• Filed: 07/22/2016
• Issued: 08/29/2017
• Est. Priority Date: 05/21/2012
• 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, Deng, Yanhua, Prucnal, Paul, McCandless, Andrew, Dourbal, Paul
• Primary Examiner(s): SANDIFORD, DEVAN A
• Application Number:
  US15/217,553
• Publication Number:
  US 20170026126A1
• Time in Patent Office: 403 Days
• CPC Class Codes: H04B 1/10 Means associated with receiver for limiting or suppressing noise or interference
• CPC Class Codes: H04B 1/1027 assessing signal quality or detecting noise/interference for the received signal
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 10/00 Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
• CPC Class Codes: H04B 10/07955 Monitoring or measuring power
• CPC Class Codes: H04B 10/2507 for the reduction or elimination of distortion or dispersion
• CPC Class Codes: H04B 10/2575 Radio-over-fibre, e.g. radio frequency signal modulated onto an optical carrier
• CPC Class Codes: H04B 17/318 Received signal strength
• CPC Class Codes: H04B 17/336 Signal-to-interference ratio [SIR] or carrier-to-interference ratio [CIR]
• CPC Class Codes: H04B 2210/006 Devices for generating or processing an RF signal by optical means
• CPC Class Codes: H04K 3/20 Countermeasures against jamming in radar G01S7/36; interference suppression in receivers H04B1/10
• 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: H04L 43/16 Threshold monitoring

Abstract

Systems and methods for cancelling interference from a received signal in order to properly detect a signal of interest are disclosed. 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, for example based on a detected output power of an optical subsystem of the interference cancellation system. 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.

Claims

1. A method for attempting to cancel interference signal, the method comprising:

receiving a first radio frequency (RF) signal corresponding to an interference signal and a second RF signal corresponding to a combined interference and signal of interest (SOI) signal;

converting the first RF signal to a first optical signal and the second RF signal to a second optical signal and applying a 180 degree phase shift to one of the first optical signal or the second optical signal before, during, or after optical conversion;

optically attenuating and optically time delaying the first optical signal;

combining the attenuated and time delayed first optical signal with the second optical signal to create a combined optical signal;

converting the combined optical signal to a combined RF signal, wherein at least one optical component is controlled by a digital control component in order to attempt to maximize cancellation of the interference signal from the combined RF signal; and

sending the combined RF signal to a radio transceiver.

2. The method of claim 1, further comprising applying an RF time delay to the first RF signal prior to convert the first RF signal to the first optical signal, wherein the RF time delay is at least an order of magnitude larger than an optical time delay that is applied to the first optical signal.

3. The method of claim 1, further comprising determining one or more initial optical attenuation values or optical delay values to be applied to the first optical signal based on a determined power difference between a signal associated with the interference signal and a signal associated with the combined interference and SOI signal.

4. The method of claim 1, further comprising:

determining when an interferer is transmitting the interferer signal and when the radio transceiver is transmitting a transmission signal;

determining to perform interference cancellation when the interferer is transmitting and the radio transmitter is not transmitting; and

determining to refrain from performing interference cancellation when the interferer is not transmitting or when the radio transceiver is not transmitting.

5. The method of claim 1, wherein combining the attenuated and time delay first optical signal with the second optical signal to create a combined optical signal results in at least 50 dB of cancellation of the interference signal from the combined interference and SOI signal.

6. The method of claim 1, wherein the at least one optical component controlled by the digital control component comprises an optical attenuator used to optically attenuate the first optical signal.

7. The method of claim 1, wherein the at least one optical component controlled by the digital control component comprises an optical time delay used to optically time delay the first optical signal.

8. The method as of claim 1, wherein the at least one optical component comprises at least one of an optical attenuator, an optical time delay line, a laser modulator, or a photodiode detector.

9. The method as of claim 1, wherein the digital control component attempts to maximize cancellation of the interference signal from the combined RF signal based on a signal received from one or more of an RF power level detector or an RF frequency detector.

10. A method comprising:

radio frequency (RF) circuitry receiving a first signal corresponding to an interferer signal and a second signal corresponding a combination of the interferer signal and a signal of interest (SOI);

converting the first and second signals from radio frequency signals to optical signals;

applying a 180 degree phase shift to the first signal;

variably attenuating and variably time delaying one or more of the first signal or the second signal in the optical domain based on one or more control signals received from a digital processor circuitry;

combining the first signal and the second signal into a combined signal after variably attenuating and variably time delaying one or more of the first signal or the second signal;

converting the combined signal into a combined RF signal; and

outputting the combined RF signal, wherein the digital processor circuitry generates the control signals based on a power level associated with the combined RF signal.

11. The method of claim 10, further comprising:

generating a third signal based on the combined RF signal output, the third signal being inversely proportional to the amount of the interference signal that has been removed from the combined RF signal, the third signal being used to generate the control signals.

12. The method of claim 11, further comprising:

determining that the power level of the third signal is below a threshold, and

sending the combined RF signal to a radio transceiver based on the power level of the third signal being below the threshold.

13. The method of claim 10, further comprising:

generating a fourth signal that indicates a frequency associated with a given RF signal.

14. The method of claim 10, further comprising:

generating

a fifth signal that indicates when a radio transceiver is performing a radio transmission.

15. A method performed by an interference cancellation system (ICS), the method comprising:

receiving a first signal corresponding to an interferer signal and a second signal corresponding a combination of the interferer signal and a signal of interest (SOI);

converting each of the first signal and the second signal from radio frequency (RF) signals to optical signals;

applying a 180 degree phase shift to one of the first signal or the second signal;

variably attenuating and variably time delaying one or more of the first signal and the second signal based on one or more control signals received from a digital processor;

combining the first signal and the second signal into a combined signal after variably attenuating and variably time delaying one or more of the first signal and the second signal; and

converting the combined signal from an optical signal to an RF signal;

sending the combined signal to a radio transceiver, wherein the control signals are generated based on a power level associated with the combined signal.

16. The method of claim 15, further comprising:

receiving a signal transmitted by the radio transceiver; and

pausing the interference cancellation process while the radio transceiver is transmitting.

17. The method of claim 15, further comprising determining a frequency associated with a signal transmitted by the radio transceiver.

18. The method of claim 15, wherein the interference signal is received from a jammer operably coupled to the ICS.