US 2003/0117319 A1 · Method and apparatus for locating the source of unknown signal

Abstract

A method of locating the source of an unknown signal of varying frequency received by receive antennas (16, 18) via relay satellites (12, 14) involves downconversion of received signals to a first intermediate frequency (IF) and band-limiting the downconverted signals. The band-limited signals are constrained to lie within a prearranged acquisition signal bandwidth by adjustment of local oscillator (LO) downconversion frequency to counteract frequency change in the unknown signal. Downconverted signals are offset in time relative to one another using trial values of differential time offset and their correlation is determined for each trial value to provide actual time offset. Compensation is provided for change in correlation phase angle, which results from signals being downconverted experiencing different LO frequencies during the time interval of the trial offset.

Claims8

Dependent claims

A method of locating the source of an unknown signal of varying frequency received by a plurality of signal relays, the method including the steps of:—

a) arranging for a plurality of receivers to receive the unknown signal via respective signal relays;
b) using a local oscillator (LO) signal to downconvert signals received by respective receivers to an intermediate frequency (IF);
c) introducing trial values of differential time offset (DTO) between received signals;
characterised in that the method also includes the steps of:—
d) constraining the downconverted signals to lie within a prearranged bandwidth by adjusting the LO signal frequency to counteract frequency change in the unknown signal;
and
e) counteracting changes in correlation phase angle of correlated signals relatively offset from one another in time and associated with differing LO frequencies by virtue of the offset and the LO signal frequency adjustment.

4 more elements

Apparatus for locating the source of an unknown signal of varying frequency received by a plurality of signal relays, the apparatus including:—

a) a plurality of receivers for receiving the unknown signal via respective signal relays;
b) a signal generator for providing a local oscillator (LO) signal to downconvert signals received by respective receivers to an intermediate frequency (IF);
c) a correlation processor for introducing trial values of differential time offset (DTO) between received signals;
characterised in that the apparatus also includes:—
d) processing means for:—
i) constraining the downconverted signals to lie within a prearranged bandwidth by adjusting the LO signal frequency to counteract frequency change in the unknown signal;
and
ii) counteracting changes in correlation phase angle of correlated signals relatively offset from one another in time and associated with differing LO frequencies by virtue of the offset and the LO signal frequency adjustment.

5 more elements

Dependencies are inferred from the claim text.

Method and apparatus for locating the source of unknown signal

Life of this patent

Method and apparatus for locating the source of unknown signal

Life of this patent

Abstract

Claims8