Patent ID: 6201499
Filing Date: 2001-03-13
Classification: G01S,H04L,H04W

Abstract:
An apparatus for measuring the time difference of arrival between two received signals, each received signal being a time delayed version of a transmitted signal, the transmitted signal being generated by a radio frequency transmitter, the transmitted signal consisting of a continuous transmission on a reverse voice channel of a frequency modulated analog voice signal plus audio tone, the audio tone having a phase that varies with time, the apparatus comprising;a remote processor including a decoder and a correlator; anda first and second sensor where each sensor includesa receiver for receiving a received signal, the received signal being a time delayed version of the transmitted signal, the receiver operable to generate a receiver output signal including an audio tone and a voice signal;an encoder for operating on the receiver output signal to generate an encoded signal where the audio tone of the receiver output signal is modeled as having a specific phase at a specific time; andmeans for transferring the encoded signal, to a remote processor;where the remote processor is operable to receive the encoded signal from one of the first and second sensors and where the decoder is operable to decode the encoded signal resulting in a reconstructed version of the received signal, the correlator operable to correlate the reconstructed version of the received signal with the received signal received by the other of the first and second sensors to derive time difference of arrival data associated with the arrival of the transmitted signal at the first and second sensors.