Patent ID: 7667649
Filing Date: 2010-02-23
Classification: G01S,H04B

Abstract:
1. In a wireless location system for use in locating a mobile transmitter, a method for improving a time difference of arrival (TDOA) estimate produced by cross-correlating a local signal with a reference signal, using either a time-domain or frequency-domain cross-correlation process, wherein the local signal is a copy of a signal transmitted by the mobile transmitter as received at a first antenna and the reference signal is a copy of the signal transmitted by the mobile transmitter as received at a second antenna, the method comprising: receiving the local signal at a first location measurement unit (LMU); processing the local and reference signals to produce a correlation function comprising a correlation-time-frequency map; searching the correlation function for a global maximum above a detection assurance threshold, and identifying a valid global maximum correlation peak; reducing the correlation-time-frequency map to a two-dimensional time-correlation timeslice centered on a frequency of the valid global maximum correlation peak; searching the two-dimensional time-correlation timeslice for a local maximum above the detection assurance threshold occurring earlier in time than the global maximum correlation peak; and performing a leading edge discovery procedure to find an earlier leading edge concealed within a correlation envelope of the two-dimensional time-correlation timeslice.