Direct sequence spread spectrum receiver and antenna array for the simultaneous formation of a beam on a signal source and a null on an interfering jammer
First Claim
1. A radio receiver for simultaneously hulling out an interference signal and enhancing a signal-of-interest that differ at least in their azimuth and/or elevation relative to the receiver, comprising:
- an antenna array with "N" number of individual antennas spatially distributed at random and providing for the reception of said interference signal and said signal-of-interest, wherein a first phase difference in the carrier frequency of said interference signal exists between any two antennas that is substantially different than a second phase difference in the carrier frequency of said signal-of-interest for said same two antennas;
multi-channel receiver down-conversion means connected to respective antennas in the antenna array; and
combining means connected to the multi-channel receiver down-conversion means for simultaneously hulling out said interference signal and enhancing said signal-of-interest based on said first and second carrier frequency phase differences;
wherein, said interference is determined to be a jammer from a set of pre-despread spatial correlation measurements and that provide for an interference autocorrelation estimate;
the combining means provides for the use of said interference autocorrelation estimate to remove said interference from a post-despread aperture vector, and which leaves only a strong signal-of-interest; and
wherein, the antenna array is adaptive and provides for simultaneous maximization of a signal-of-interest and a minimization of both narrowband and wideband jamming interference from a variety of directions that can vary in real-time by providing for an adjustment of a plurality of direct sequence spread spectrum (DSSS) local code phases once a code and a code phase lock have been achieved to effectively aim an antenna-array-reception-pattern null in a direction of a jammer.
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Accused Products
Abstract
A navigation satellite receiver that nulls interference and enhances satellite signals using differences in their spatial positions and that includes four antennas in a spatial array respectively connected to four amplitude and phase balanced receiver downconverter channels. Five satellite tracking channels are each connected to all four receiver channels and each includes despreaders and I/Q accumulators for early, late and punctual correlation. The despreader and accumulator combinations provide four-by-one vectors called aperture estimates. A code-gated maximum likelihood processor whitens these by multiplication with the mathematical inverse Cholesky factor of the interference data. This vector is generated in a millisecond block "k" and is multiplied by a similarly generated vector formed in a previous millisecond block "k-1". The magnitude of the resulting product is used for code tracking, and the phase of the result provides for carrier tracking.
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Citations
13 Claims
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1. A radio receiver for simultaneously hulling out an interference signal and enhancing a signal-of-interest that differ at least in their azimuth and/or elevation relative to the receiver, comprising:
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an antenna array with "N" number of individual antennas spatially distributed at random and providing for the reception of said interference signal and said signal-of-interest, wherein a first phase difference in the carrier frequency of said interference signal exists between any two antennas that is substantially different than a second phase difference in the carrier frequency of said signal-of-interest for said same two antennas; multi-channel receiver down-conversion means connected to respective antennas in the antenna array; and combining means connected to the multi-channel receiver down-conversion means for simultaneously hulling out said interference signal and enhancing said signal-of-interest based on said first and second carrier frequency phase differences; wherein, said interference is determined to be a jammer from a set of pre-despread spatial correlation measurements and that provide for an interference autocorrelation estimate; the combining means provides for the use of said interference autocorrelation estimate to remove said interference from a post-despread aperture vector, and which leaves only a strong signal-of-interest; and wherein, the antenna array is adaptive and provides for simultaneous maximization of a signal-of-interest and a minimization of both narrowband and wideband jamming interference from a variety of directions that can vary in real-time by providing for an adjustment of a plurality of direct sequence spread spectrum (DSSS) local code phases once a code and a code phase lock have been achieved to effectively aim an antenna-array-reception-pattern null in a direction of a jammer. - View Dependent Claims (2)
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3. A radio receiver for simultaneously nulling out an interference signal and enhancing a signal-of-interest that differ at least in their azimuth and/or elevation relative to the receiver, comprising:
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an antenna array with individual antennas spatially distributed and providing for the reception of said interference signal and said signal-of-interest, wherein a first phase difference in the carrier frequency of said interference signal exists between any two antennas that is substantially different than a second phase difference in the carrier frequency of said signal-of-interest for said same two antennas; multi-channel receiver down-conversion means connected to respective antennas in the antenna array; combining means connected to the multi-channel receiver down-conversion means for simultaneously nulling out said interference signal and enhancing said signal-of-interest based on said first and second carrier frequency phase differences; the antenna array provides for the reception of L-band microwave radio transmissions from orbiting navigation satellites as said signal-of-interest and said interference signal includes transmissions from a jammer; the multi-channel receiver down-conversion means provides for code and carrier tracking of direct sequence spread spectrum (DSSS) types of transmissions in said L-band microwave radio transmissions; the combining means includes aperture estimate formation means including in-phase (I) and quadrature (Q) despreaders and accumulators for early, late and puntual correlation of said DSSS transmissions, wherein said despreaders and accumulators provide for a continuous output of aperture estimates; and the combining means further comprises a code-gated maximum-likelihood (CGML) processor connected to the multi-channel receiver down-conversion means for whitening said aperture estimates with means for taking an inverse Cholesky factor of a pre-despread interference data, wherein the magnitude of a resulting products provide for code tracking and the phase of the result provides for carrier tracking. - View Dependent Claims (4, 5)
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6. A navigation satellite receiver for hulling-out interference and enhancing satellite signals by using differences in the spatial positions of the signal sources, comprising:
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a plurality of antennas in a spatial array providing for the reception of L-band microwave radio transmissions from orbiting navigation satellites and subject to interference from jammers; a plurality of amplitude-balanced and phase-balanced receiver downconverter channels one each respectively connected to individual ones of the plurality of antennas; a plurality of satellite tracking channels each one connected to every one of the plurality of receiver channels and each including in-phase (I) and quadrature (Q) despreaders and accumulators for early, late and punctual correlation, wherein said despreaders and accumulators provide four-by-one vectors as aperture estimates; and a code-gated maximum likelihood (CGML) processor connected to the satellite tracking channels for voltage-domain whitening of said aperture estimates by an inverse Cholesky factor of a pre-despread interference data, wherein the magnitude of a resulting product provides information for code tracking and the phase of the result provides information for carrier tracking. - View Dependent Claims (7, 8, 9, 10, 11, 12, 13)
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Specification