Patent ID: 6137842
Filing Date: 2000-10-24
Classification: G01S

Abstract:
A system for determining the time difference of arrival of a signal between two separate locations, comprising:a first receiver located at a first site for generating first signal samples representing an FSK signal in response to receiving the FSK signal at time T.sub.A ;a second receiver located at a second site for generating second signal samples representing the FSK signal in response to receiving the FSK signal at time T.sub.B, where T.sub.A .noteq.T.sub.B ;a first computer for estimating a first set of frequency shift times of the FSK signal in response to receiving the first signal samples and a time reference signal, and for generating a first output signal representing the first set of frequency shift times; anda second computer for estimating a second set of frequency shift times of the FSK signal using the second signal samples and time reference signal, and for determining the time difference of arrival of the FSK signal between the first and second receivers using the first output signal, and the second set of frequency shift times in accordance with the relation:TDOA={[t.sub.2 (1)-t.sub.1 (1)]+[t.sub.2 (2)-t.sub.1 (2)]+[t.sub.2 (3)-t.sub.1 (3)] . . . +[t.sub.2 (K)-t.sub.1 (K)]}/(K),where {t.sub.1 (1), t.sub.1 (2), t.sub.1 (3), . . . t.sub.1 (K)} represent a K number of first frequency shift times within an N number of the first signal samples, {t.sub.2 (1), t.sub.2 (2), t.sub.2 (3), . . . t.sub.2 (K)} represent a K number of second frequency shifts times within an N number of the second signal samples, and where K and N are positive integers.