US 6,845,240 B2 · System and method for analog cellular radio geolocation

A method for geolocating a mobile appliance transmitting an FM analog signal which can be received by a plurality of wireless location sensors each including at least one antenna, comprising the steps of:

(a) sending a first geolocation reference signal from each of a plurality of wireless location sensors to a central node, comprising the steps of:
(i) receiving a first FM analog signal on one or more of the at least one antennas;
(ii) digitizing the received signals;
(iii) time-stamping the digitized signals;
(iv) combining the time-stamped signals if received on more than one antenna;
(v) providing a location identification stamp for the combined signal to thereby produce a first location-identified signal;
(vi) frequency demodulating the first location-identified signal;
(vii) transforming the demodulated signal from the time domain to the frequency domain;
(viii) providing the first geolocation reference signal including a select portion of the frequency domain signal;
and
(ix) sending the first geolocation reference signal to a central node;
(b) determining at the central node a primary wireless location sensor including the steps of:
(i) receiving the first geolocation reference signals from each of the plurality of wireless location sensors;
(ii) providing a predetermined quality factor;
(iii) comparing each of the first geolocation reference signals with the predetermined quality factor to thereby determine a primary geolocation reference signal;
(iii) identifying a primary wireless location sensor from the location identification stamp for the primary geolocation reference signal;
and
(iv) sending a control signal to the primary wireless location sensor;
(c) receiving a second FM analog signal at each of the plurality of wireless location sensors, comprising the steps of:
(i) repeating steps (a)(i) through (a)(v) for said second FM analog signal to thereby produce a second location-identified signal;
and
(ii) buffering the second location-identified signal to thereby produce a buffered signal;
(d) sending a reference signal from the primary wireless location sensor to the central node, comprising the steps of:
(i) repeating steps (a)(vi) and (a)(vii) for the second location-identified signal in response to receipt of the control signal from the central node;
(ii) providing the reference signal including a select portion of the frequency domain signal from step (d)(i);
and
(iii) sending the reference signal to the central node;
(e) sending the reference signal from the central node to each one of the plurality of wireless location sensors in response to receipt at the central node of the reference signal from the primary wireless location sensor;
(f) sending a geolocation time of arrival signal from each of the plurality of wireless location sensors to a central node, comprising the steps of:
(i) receiving the reference signal from the central node;
(ii) transforming the reference signal from the frequency domain to the time domain to thereby create a time domain reference signal;
(iii) providing a carrier signal representative of the FM analog signal carrier wave;
(iv) modulating the carrier signal with the time domain reference signal;
(v) comparing the buffered signal with the time domain reference signal to thereby determine the time of arrival of the second FM analog signal at the wireless location sensor;
and
(vi) sending the geolocation time of arrival signal which is representative of the time of arrival of the second FM analog signal to the central node;
(g) receiving the geolocation time of arrival signals from the plurality of wireless location sensors;
(h) determining the geolocation of the mobile appliance at the central node from the geolocation time of arrival signals.

35 more elements

A method for geolocating a mobile appliance transmitting an FM analog signal which can be received by a plurality of wireless location sensors, comprising the steps of:

(a) receiving a first FM analog signal at each of the plurality of wireless location sensors;
(b) sending a first geolocation reference signal from each of the plurality of wireless location sensors to a central node wherein said first geolocation reference signal is a digitized, time and location stamped frequency domain signal including a select portion of the first FM analog signal;
(c) determining at the central node a primary geolocation reference signal by comparing each of the first geolocation reference signals with a predetermined quality factor to thereby determine a primary geolocation reference signal and designating the wireless location sensor that sent the primary geolocation reference signal as the primary wireless location sensor;
(d) sending a control signal to the primary wireless location sensor;
(e) receiving a second FM analog signal at each of the plurality of wireless location sensors and buffering the digitized, time and location stamped second FM analog signal to thereby create a buffered signal;
(f) sending a first reference signal from the primary wireless location sensor to the central node wherein said reference signal comprises a digitized, time and location stamped frequency domain signal including a select portion of the second FM analog signal;
(g) sending the first reference signal from the central node to each one of the plurality of wireless location sensors in response to receipt at the central node of the first reference signal from the primary wireless location sensor;
(h) receiving the first reference signal from the central node at each of the plurality of wireless location sensors;
(i) providing at each of the plurality of wireless location sensors a second reference signal comprising a time domain FM modulated version of the first reference signal;
(j) comparing at each of the plurality of wireless location sensors the buffered signal to the second reference signal to thereby determine the time of arrival of the second FM analog signal at each of the plurality of wireless location sensors;
(k) sending a geolocation time of arrival signal from each of the plurality of wireless location sensors to a central node wherein the geolocation time of arrival signal is representative of the time of arrival of the second FM analog signal;
(l) receiving at the central node the geolocation time of arrival signals from the plurality of wireless location sensors;
(m) determining the geolocation of the mobile appliance at the central node from the geolocation time of arrival signals.

10 more elements

A geolocation system for geolocating a mobile appliance transmitting an FM analog signal which can be received by a plurality of wireless location sensors comprising:

a plurality of wireless location sensors each including at least one antenna comprising:
(a) a receiver for receiving FM analog signals from ones of the at least one antennas;
(b) a first interface circuit for sending signals to a central node and for receiving signals from the central node;
(c) a first signal processing circuit comprising:
(i) a digitizer for digitizing the received FM analog signals;
(ii) time-stamping means for time-stamping the digitized signals;
(iii) a combiner for combining the time-stamped signals;
and
(iv) location identification stamping means for providing a location identification stamp for the combined signal to thereby create a location-identified signal;
(d) a second signal processing circuit for producing a reference signal comprising:
(i) a demodulator for frequency demodulating the location-identified signal;
(ii) first transforming means for transforming the demodulated signal from the time domain to the frequency domain;
and
(iii) selecting means for selecting a portion of the frequency domain signal to thereby produce the reference signal;
(e) a third signal processing circuit for producing a geolocation reference signal comprising:
(i) a buffer for buffering the location-identified signal to thereby produce a buffered signal;
(ii) second transforming means for transforming a reference signal sent by the central node from the frequency domain to the time domain to thereby produce a time domain reference signal;
(iii) first circuit means for providing a carrier signal representative of the FM analog signal carrier wave;
(iv) a modulator for modulating the carrier signal with the time domain reference signal;
(v) a first comparator for comparing the buffered signal with the time domain reference signal to thereby determine the time of arrival of an FM analog signal at said at least one antennas;
and
(vi) second circuit means for producing the geolocation reference signal representative of said time of arrival of an FM analog signal;
a central node comprising:
(a) a second interface circuit for sending signals to the plurality of wireless location sensors and for receiving signals from the wireless location sensors;
(b) second circuit means for providing a predetermined quality factor;
(c) a second comparator for comparing the reference signals from each of the plurality of wireless location sensors with the predetermined quality factor to thereby determine a primary geolocation reference signal;
(d) third circuit means for identifying a primary wireless location sensor from the location identification stamp for the primary geolocation reference signal;
(e) fourth circuit means for producing a control signal to be sent to the primary wireless location sensor;
and
(f) a fourth signal processing circuit for determining the geolocation of the mobile appliance at the central node from the geolocation reference signals.

27 more elements

System and method for analog cellular radio geolocation

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System and method for analog cellular radio geolocation

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Abstract

Claims13