Patent ID: 7844280
Filing Date: 2010-11-30
Classification: G01S,H04L

Abstract:
1. A system for locating wireless transmitters employing an Orthogonal Frequency Division Multiplexing (OFDM) digital modulation scheme, wherein said OFDM scheme comprises transmitting signal components over a plurality of narrowband frequency channels spanning a wideband channel, comprising: a first receiving system configured to receive a fraction of the signal components transmitted by a first wireless transmitter to be located in a fraction of the narrowband frequency channels, and to process said fraction of the signal components to derive location related measurements, wherein said fraction of the narrowband frequency channels includes at least one pilot channel in which said first wireless transmitter transmits energy, and wherein the first receiving system is configured to use signal components in said pilot channel to aid in signal acquisition and demodulation; wherein said first receiving system comprises a first frequency conversion circuit configured to convert a first received RF signal component to a first digital baseband OFDM signal; a Fast Fourier Transform (FFT) circuit configured to perform an FFT of the first digital baseband OFDM signal provided by the first frequency conversion circuit; a demodulation circuit configured to produce coded bits based on the output of the FFT circuit; a first reconstruction circuit configured to reconstruct the first digital baseband OFDM signal based on the coded bits produced by the demodulation circuit; and a first correlation processing system configured to correlate the first reconstructed digital baseband OFDM signal with the first digital baseband OFDM signal, wherein a correlation function peak is indicative of a first time of arrival for the first received RF signal component; a second receiving system configured to receive said fraction of the signal components transmitted by said first wireless transmitter, and to process said fraction of the signal components to derive location related measurements, wherein the second receiving system is configured to use signal components in said pilot channel to aid in signal acquisition and demodulation; wherein said second receiving system comprises a second reconstruction circuit configured to receive the coded bits produced by the first demodulation circuit of the first receiving system and to produce the first reconstructed digital baseband OFDM signal; and a second correlation processing system configured to correlate the first reconstructed digital baseband OFDM signal with a second digital baseband OFDM signal derived by the second receiving system, wherein a peak of the correlation function is indicative of a second time of arrival for the RF signal as received at the second receiving system; and a processing system, operatively coupled to said first and second receiving systems, wherein said processing system is configured to use location related measurements from said first and second receiving systems, including the first and second times of arrival, to compute the location of said first wireless transmitter.