Waveform-enabled jammer excision (WEJE)

Patent metadata

Field	Value
Publication number	US-9712275-B2
Application number	US-201313971813-A
Country	US
Kind code	B2
Filing date	Aug 20, 2013
Priority date	Aug 22, 2012
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

A method for waveform-enabled jammer excision (WEJE) may include performing a jammer measurement during a look-through window when no signal-of-interest (SOI) is present and obtaining a jammer signal. A SOI-plus-jammer measurement may be performed and a SOI-plus-Jammer signal may be obtained when both the jammer signal and the SOI are present. Optimal weights that maximize a SOI-to-jammer power ratio may be determined. SOI-plus-jammer signals from a number of antenna elements may be optimally weighted and combined to copy the SOI and null the jammer signal based on the determined optimal weights.

First claim

What is claimed is:

1. A method for waveform-enabled jammer excision (WEJE), the method comprising:
performing a jammer measurement across each frequency sub-band of a full-spreading bandwidth during a look-through window comprising a predefined frequency-hop time-slot when no signal-of-interest (SOI) is transmitting and obtaining a jammer signal, wherein the look-through window is characterized by a frequency and a bandwidth;
performing a SOI-plus-jammer measurement and obtaining a SOI-plus-jammer signal when both the jammer signal and the SOI are present;
determining optimal weights that maximize a SOI-to-jammer power ratio by using the measured jammer signal and SOI-plus-jammer signal;
optimally weighing and combining SOI-plus-jammer signals associated with a number of antenna elements to copy the SOI and null the jammer signal based on the determined optimal weights; and
performing beam-forming and jammer signal nulling using three multi-beam antennas (MBAs) arranged in a triangle on a satellite, and forming 2*B jammer nulls, wherein each MBA includes B beams and B is greater than seven.

2. The method of claim 1 , wherein the jammer measurement comprises:
at least one of a spatial or temporal interference measurement,
a jammer characteristics and aperture measurement; and
a jammer auto-correlation measurement.

3. The method of claim 1 , wherein:
the SOI-plus-jammer measurement comprises a SOI-plus-jammer auto-correlation measurement,
the SOI comprises a pure time-division multiple-access (TDMA) signal, or a wide-band frequency-hopped (FH)-TDMA signal, and
the optimal weights comprise optimal SOI beam-forming and jammer nulling weights.

4. The method of claim 1 , wherein the look-through window is characterized by a time-slot, and wherein performing the method is independent of direction of arrivals of the jammer signal and the SOI.

5. The method of claim 1 , wherein the jammer signal comprises a broadband jammer signal, a partial-band jammer signal, and a pulsed jammer signal, and wherein determining optimal weights comprises optimizing SOI-to-interference-plus noise ratio for individual users.

6. The method of claim 1 , wherein nulling the jammer signal comprises forming one or more deep nulls over a wide bandwidth, wherein nulling the jammer signal is performed in conjunction with adaptive modulation and coding, and wherein nulling the jammer signal allows sparse aperture nulling (SAN) by using sparse aperture antenna element spacing.

7. The method of claim 1 , further comprising copying SOIs within the beams.

8. The method of claim 1 , further comprising beam-forming and nulling that is performed by using multiple antenna elements with different gains, and wherein beam-forming and nulling is performed via pseudo-inverse decomposition, singular value decomposition (SVD), or generalized SVD when autocorrelation matrices are ill-conditioned.

9. A system for waveform-enabled jammer excision (WEJE), the apparatus comprising:
a plurality of antennas configured to enable communication over a coverage area through a plurality of antenna beams;
a plurality of radio circuits coupled to the plurality of antennas and configured to measure a jammer signal across each frequency sub-band of a full-spreading bandwidth during a look-through window comprising a predefined frequency-hop time-slot when during which no signal-of-interest (SOI) is transmitting and to measure SOI-plus-jammer signal when both the jammer signal and the SOI are present, wherein the look-through window is characterized by a frequency and a bandwidth;
a weight processor coupled to the plurality of radio circuits and configured to:
receive the jammer signal during the look-through window and to receive the SOI-plus-jammer signal; and
determine optimal weights that maximize a SOI-to-jammer power ratio;

a baseband processor coupled to the plurality of radio circuits and the weight processor and configured to:
receive the jammer signal and the SOI-plus-jammer signal from the plurality of radio circuits;
receive the optimal weights from the weight processor;
optimally weigh and combine the SOI-plus-jammer signals associated with a number of antenna elements to optimally copy the SOI and null the jammer signal based on the determined optimal weights; and
perform beam-forming and jammer signal nulling using three multi-beam antennas (MBAs) arranged in a triangle on a satellite, and form 2*B jammer nulls, wherein each MBA includes B beams and B is greater than seven.

10. The system of claim 9 , wherein the plurality of antennas comprise a single multi-beam antenna (MBA), separate gimbaled dish antenna (GDA), or an array of antennas, and wherein the apparatus is configured to perform the WEJE without knowledge of an antenna configuration including an antenna array aperture.

11. The system of claim 9 , wherein:
the radio circuit comprises a de-hopping circuit and a down-converter mixer,
the de-hopping circuit is configured to:
isolate the hopping bandwidth of the SOI;
operate orthogonally to SOI hops; and
allow measurement of pure jammer autocorrelation matrix without the look-through window,

the down-converter mixer is configured to down-convert the SOI to baseband, and
the SOI comprises a pure time-division multiple-access (TDMA) signal, or a wide-band frequency-hopped (FH)-TDMA signal.

12. The system of claim 9 , wherein the baseband processor is configured to perform:
at least one of a spatial or temporal interference measurement,
a jammer characteristics and aperture measurement;
a jammer auto-correlation measurement; and
a SOI-plus-jammer auto-correlation measurement.

13. The system of claim 9 , wherein:
the weight processor is further configured to determine the optimal weights that comprise optimal SOI beam-forming and jammer nulling weights,
the weight processor is further configured to determine the optimal weights by using one of a plurality of techniques including Cholesky decomposition, singular-value decomposition (SVD), pseudo-inverse decomposition, and generalized SVD,
the look-through window is characterized by a time-slot, and optimal SOI beam-forming and jammer nulling weights do not require information on direction of arrivals of the jammer and the SOI.

14. The system of claim 9 , wherein:
the jammer signal comprises a broadband jammer signal, a partial-band jammer signal, and a pulsed jammer signal,
the weight processor is further configured to optimize SOI-to-interference-plus noise ratio for individual users,
the baseband processor is capable of nearly instantaneously forming beams on each user individually and nulling on interferers for FH-TDMA and TDMA signals, and
the baseband processor is capable of leveraging beam-forming gain to make disadvantaged terminals harder to detect.

15. The system of claim 9 , wherein:
the baseband processor comprises a plurality of finite-impulse response (FIR) filters each coupled to one of the plurality of antennas,
the baseband processor is configured to receive optimal weights that are characterized by a plurality of indices,
the plurality of indices comprise a first index that indicates a user, a second index that represents a frequency sub-band, a third index that indicates an antenna number associated with each of the plurality of antennas, and a fourth index that is an index that represents a temporal tap.

16. The system of claim 9 , wherein the baseband processor is further configured to:
null the jammer signal by forming one or more deep nulls over a wide bandwidth, wherein nulling the jammer signal is performed i

Assignees

• Lockheed Corp

Inventors

• Johnson Russell K
• Ivey James Alan
• Zambre Yadunath Bhagvantrao

Classifications

• H01Q3/2605

  Array of radiating elements provided with a feedback control over the element weights, e.g. adaptive arrays · CPC title

• H04K3/44 Primary

  characterized by the control of the jamming waveform or modulation type · CPC title

• H04K3/228

  Elimination in the received signal of jamming or of data corrupted by jamming (interference suppression in receivers H04B1/10) · CPC title

• H01Q3/2617

  Array of identical elements · CPC title

• H04K2203/32

  including a particular configuration of antennas · CPC title