Lockheed Martin Corporation

Loral Federal Systems Company

Lockheed Martin Mission Systems

Robert H Benner

Kevin W Baugh

Richard A Lodwig

Henry Michaels Beisner

Gregory A Baker

Jack George Rudd

Joseph Sawyer

Jon Rucker

John S Rucker

A system and method for narrowband pre-detection signal processing in passive coherent location applications is disclosed. A receiving subsystem receives a reference signal and a target signal from an uncontrolled transmitter. The target signal is reflected from a target. The passive coherent location system includes subprocessors that perform pre-detection operations on the reference and target signals. The functions include zero-doppler cancellation, quadrature demodulation, reference beam regeneration, coherent processing interval selection, power spectral density estimation, cross ambiguity function formation, and the like. Within these operations, the reference signal is filtered with respect to the target signal to form a first output reference signal. The first output reference signal is combined with the first target signal to form a first output target signal. The output target signal then is used for subsequent passive coherent location processing operations. The filter is updated with respect to a difference between the target signal and a subsequent target signal. Further, two paths are used for correlation processing of the reference and target signals.

System and method for narrowband pre-detection signal processing for passive coherent location applications

A civil aviation passive coherent location system and method is disclosed. A receiver subsystem receives reference transmissions from an uncontrolled transmitter. The receiver subsystem also receives scattered transmissions originating from the uncontrolled transmitter and scattered by an airborne object. The received transmissions are compared to determine measurement differentials, such a frequency-difference-of-arrival, a time-difference-of-arrival and an angle of arrival. From the measurement differentials, an object state estimate is determined. A previous state estimate may be updated with the determined state estimate. Processing subsystems determine the measurement differentials and state estimates.

Civil aviation passive coherent location system and method

A system and method for narrowband pre-detection signal processing in passive coherent location applications is disclosed. A receiving subsystem receives a reference signal and a target signal from an uncontrolled transmitter. The target signal is reflected from a target. The passive coherent location system includes sub-processors that perform pre-detection operations on the reference and target signals. The functions include zero-doppler cancellation, quadrature demodulation, reference beam regeneration, coherent processing interval selection, power spectral density estimation, cross ambiguity function formation, and the like. Within these operations, the reference signal is filtered with respect to the target signal to form a first output reference signal. The first output reference signal is combined with the first target signal to form a first output target signal. The output target signal then is used for subsequent passive coherent location processing operations. The filter is updated with respect to a difference between the target signal and a subsequent target signal. Further, two paths are used for correlation processing of the reference and target signals.

A system and method for wideband pre-detection signal processing for PCL applications is disclosed. The method includes receiving an input signal, implementing a transformation operation on the input signal, compensating the input signal for channel distortion, demodulating and forming complex-valued representations of the compensated input signal, estimating a reference signal and a target signal from the demodulated input signal, reducing a portion of the reference signal in the target signal, wherein the reference signal is adaptively filtered with respect to the target signal and combined with the target signal to form an output target signal, implementing an inverse transformation operation on the output target signal and the reference signal, forming a plurality of target beams for the output target signal, forming a plurality of decimated lag products for each of the plurality of target beams, forming a plurality of decimated lag products for the reference signal, estimating a cross ambiguity function for the each of plurality of target beams using the plurality of decimated lag products for each of the plurality of target beams, and estimating an auto ambiguity function for the reference signal using the plurality of decimated lag products for the reference signal.

System and method for wideband pre-detection signal processing for passive coherent location applications

A system and method for measurement domain data association in a passive coherent location system is disclosed. According to the system and method, detection reports are received and associated with line tracks. The detection reports correlate to target signals received at the passive coherent location system. Measurements of the detection report correlate to the data of the target signals. A line track state estimation function associates new detection reports with the line tracks and estimates update states for the line tracks. A signal type is determined. Kalman filters are selected for the measurements according to the signal type. Measurement residuals are computed for the detection reports according to the Kalman filters. The detection reports are selected for association with the line tracks according to the residuals. The line tracks can be merged or terminated during updates according to specific criteria. Further, new line tracks are initialized as new targets are detected.

System and method for measurement domain data association in passive coherent location applications

A system and method for detection and feature extraction in a passive coherent location system is disclosed. During a coherent processing interval, detection and feature extraction operations are performed to determine peak detections and target parameters for targets. The system forms an ambiguity surface that has ambiguity surface data or the coherent processing interval. Bins from a previous ambiguity surface are associated with the ambiguity surface data. New bins are identified for new target echoes within the ambiguity surface. Peak detections are formed from the bins. The peak detections correlate to the target echoes of the coherent processing interval. Target parameters for the targets are estimated from the peak detections.

System and method for detection and feature extraction in passive coherent location applications

A system and method for central association and tracking for PCL applications is disclosed. Detection reports are received at a target tracking processing system. The detection reports include measurements correlating to line tracks associated with target echoes in earlier processing operations. In addition, other information, such as parameters and observables, are received by the target track processing system. The target track processing system performs a line track association function and a track filtering function on the line tracks according to the measurements within the detection reports. These operations also predict and estimate target parameters for tracking. Target parameters are extrapolated from the propagated and updated target tracks, and fed to a display for a user, or back into the PCL system for further processing.

System and method for central association and tracking in passive coherent location applications

A system and method for enhancing object state awareness is disclosed. The system includes a receiver subsystem that receives reference signals from an uncontrolled transmitter and scattered transmissions originating from the uncontrolled transmitter and scattered by an object. The system also includes a front-end processing subsystem that determines a radial velocity of the object based on the received transmissions. The system also includes a back-end processing subsystem that determines object state estimates based on the determined radial velocity.

Passive coherent location system and method

In a global monitoring system having four or more satellites which transmit messages to user stations by which the user stations can determine the user position, the satellite messages include the time of transmission of the messages as indicated by satellite clocks and includes a correction message. The correction message consists of time correction values for the satellite clocks. The satellite time correction values are determined from a clocks only model wherein three or more monitoring stations having known positions on the ground receive the satellite messages and determine pseudoranges between the satellites and the monitoring stations. The satellite time correction values are determined statistically by nonlinear least squares from a clocks only model relating the ranges between the satellites and the monitoring stations to the measured pseudoranges, the satellite time correction values and monitoring stations time correction values.

Global positioning system employing clocks only model

In a system for detecting the position and trajectory of a target, Doppler measurements from a bistatic continuous wave radar system are used exclusively to provide information about the target. Radar signals are transmitted to the target by a plurality of transmitters and at least one receiver is provided to receive the signals from the target and make Doppler measurements. A nonlinear least squares estimator is used to estimate the initial target position and a Kalman filter is used to predict the target trajectory from the initial position assumed by the NLS estimator and from the Doppler measurements. The Kalman filter also generates a set of predicted Doppler measurements from the predicted trajectory. The nonlinear least squares estimator is used to compute a correction to the estimated initial position from partial differentials of the initial position and from the differences between the predicted and actual Doppler measurements. The difference between the actual Doppler measurements and the predicted Doppler measurements are also used to generate a test statistic as an indication of the accuracy of the predicted trajectory.

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Gaithersburg, MD, United States of America

Robert H Benner