Skybitz, Inc.

Eagle-eye, Inc.

Information Systems Laboratories, Inc.

Raytheon E-systems, Inc.

Argon Engineering

Mark C Sullivan

James B Kilfeather

Darryl S Bierly

Phillip Donald Harvey

Joseph Patrick Kennedy, Jr

A GPS receiver acquires carrier frequency and Gold code phase using short segments of a received GPS signal. In one embodiment, a 1-ms segment of the GPS signal is transformed to the frequency domain. This is multiplied by a frequency representation of the Gold code. The resulting product is converted to the time domain, and a peak is detected. The location of the peak corresponds to the code phase. If no peak is located, the carrier frequency is changed. Full- and half-bin steps in carrier frequency are considered. Processing gain is achieved by using longer segments of the input signal, for example 4 or 16 ms and integrating 1-ms segments. Considerations are provided for compensating for the effects of a transition, should it occur in the short segment of the GPS signal being processed. Integrations can be performed using non-coherent and coherent techniques. Adjustments are made for non-integral millisecond segment lengths.

System and method for fast code phase and carrier frequency acquisition in GPS receiver

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay this observation data to the processor. The range from the satellite (or other airborne transponder) to the terminal is determined using the known positions of an interrogating transmitter and a satellite, and a known terminal delay between the received signal and the transmission of the return signal, and the round trip time. An arc of locations is determined by computing an intersection of a sphere centered at the satellite having a radius given by the calculated range with a model of the Earth's surface. The candidate points are considered and refined using code phase measurements from a set of GPS satellites. The candidate point having the lowest residuals or expected to measured code phases is chosen as the location of the mobile terminal. The measurements can be refined to account for various sources of error including measurement bias, relative motion and timing errors.

System and method for fast acquisition position reporting

A range of a frequency measuring device having limited range is extended by pre-processing an input signal. The input signal is divided into a plurality of channels. In each channel, the input signal is divided into sub-bands. A frequency of the input signal is determined using a frequency measuring device having limited range. The frequencies are stored in a frequency set. The frequency set is used to determine a frequency associated with the input signal according a set of pre-determined reconstruction rules.

System and method for extending the range of a frequency measuring device

A frequency translator uses a CORDIC phase rotator coupled to a phase accumulator to translate an input signal in frequency. The CORDIC phase rotator performs required phase angle rotations of input vectors using only shift and add operations. Thus, the frequency translator can be readily implemented in hardware. Higher precision arithmetic is used in the CORDIC phase rotator operations than the input vectors contain. To avoid truncation error at the output of the CORDIC phase rotator, stochastic rounding is employed. A dither signal is added to avoid errors due to nonlinear operation of D/A converters, where D/A conversion of the frequency translated signal is required.

Frequency translator using a cordic phase rotator

A GPS receiver acquires carrier frequency and Gold code phase using short segments of a received GPS signal. In one embodiment, a 1-ms segment of the GPS signal is transformed to the frequency domain. This is multiplied by a frequency representation of the Gold code. The resulting product is converted to the time domain, and a peak is detected. The location of the peak corresponds to the code phase. If no peak is located, the carrier frequency is changed. Full- and half-bin steps in carrier frequency are considered. Processing gain is achieved by using longer segments of the input signal, for example 4 or 16 ms and integrating 1-ms segments. Considerations are provided for compensating for the effects of a transition, should it occur in the short segment of the GPS signal being processed. Integrations can be performed using non-coherent and coherent techniques.

System and method for fast acquisition reporting using communication satellite range measurement

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay this observation data to the processor. The range from the satellite (or other airborne transponder) to the terminal is determined using the known positions of an interrogating transmitter and a satellite, and a known terminal delay between the received signal and the transmission of the return signal, and the round trip time. An arc of locations is determined by computing an intersection of a sphere centered at the satellite having a radius given by the calculated range with a model of the Earth's surface. Alternatively, candidate locations that are consistent with the carrier signal received from GPS satellites can be used. In either case, the candidate points are considered and refined using code phase measurements from a set of GPS satellites. The candidate point having the lowest residuals or expected to measured code phases is chosen as the location of the mobile terminal. The measurements can be refined to account for various sources of error including measurement bias, relative motion and timing errors.

System and method for rapid telepositioning

A geographic tracking system with minimal power and size required at the mobile terminal collects observation data at the mobile terminal, forwards the data to a processor, which calculates the position. The mobile terminal needs only to gather a few milliseconds of observation data, and to relay this observation data to the processor. The range from the satellite (or other airborne transponder) to the terminal is determined using the known positions of an interrogating transmitter and a satellite, and a known terminal delay between the received signal and the transmission of the return signal, and the round trip time. An arc of locations is determined by computing an intersection of a sphere centered at the satellite having a radius given by the calculated range with a model of the Earth's surface. Only that portion of the arc within the region bounded by the satellite beam pattern is retained. Next, the time when the mobile terminal collected the GPS signal is determined. A satellite orbit model estimates the positions of the GPS satellites at their time of transmission. Using discrete points on the arc as an initial guess, an iterative least squares technique fits the observation data to the predicted data and minimizes residual error. After convergence, this estimated position solution is then screened against the known satellite range, satellite beam boundaries, an acceptable altitude range, and a maximum residual threshold. Those position estimates not meeting these criteria are discarded. The remaining points are then subjected to a final improved position estimate and residual calculation and the best point is selected.

Fast acquisition position reporting system

A wireless system for locating a signal emitter includes at least three base stations for receiving the emitter signal, and a central processing site for converting information from the received signals into range estimates. Specifically, an antenna array at each base station for receives the emitter signal, and a beamformer isolates the direct path component of this received signal from interference and multi-path signals using cyclic phase minimizer techniques. In operation, an extractor is used to separate a cyclostationary feature from the direct path component of the emitter signal, and the cyclostationary feature is identified in an absolute time reference. The identified cyclostationary feature is then passed to the central processing site. At the central processing site, phase delay characteristics of the cyclostationary features from all participating base stations are compared with each other to obtain phase difference measurements. These phase difference measurements are then converted into differential range estimates for locating the emitter.

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Annandale, VA, United States of America

Mark C Sullivan