Abstract: An accurate location system 10 for use in locating the position of a tracked unit 16 having at least a first and a second transmitter 14, 22 for propagating at least first and second signals and a master station 12 for receiving and storing the first and second signals, respectively. The tracked unit 16 receives and operates on the first and second signals from the first and second transmitters 14, 22, respectively, for providing third and fourth signals which are transponded to the master station 12. A correlation detector 40 located within the master station 12 receives and cross-correlates the transponded third and fourth signals with the stored first and second signals within the master station for determining the additional times of flight (.tau.) of the third and fourth signals transponded to the master station. The locus of points of constant (.tau.

Abstract: Position location processing using a series of processing routines for enhanced position location in a hyperbolic ranging system adapted to more accurately indicate the position of mobile transmitters within the system. These routines incorporate data in an overdetermined system to refine the position estimate and speed up computation time. The processing utilizes all data received and filters out data caused by radio propagation measurement error that contributes to overall position error. It selects the optimum subset of data to process prior to performing time-intensive mathematical operations which results in a substantial reduction in computation time, allowing for many more overall position computations per second. The advantages of the present position location processing include its ability to incorporate all data received to reduce the overall position error. Processing filters that provide for data extraction and position verification enhance the accuracy and reliability of the position estimate.

Abstract: Method and apparatus are disclosed for improving the anti-jam performance of a processing circuit to increase conversion gain and reduce small signal suppression resulting from processing a phase modulated input signal accompanied by jamming interference. Input signals are each segregated into signal chips by a matched filter 23, and by an adaptive threshold circuit 13 in accordance with a predetermined relative threshold. The threshold is set to repeatedly distinguish a predetermined number of signal chips having greater signal amplitude. The absolute amplitude threshold level may, therefore, vary in accordance with the particular signal chips forming each input signal segment. A phase quantizer 29 operates to extract phase information from the signal chips.