Transmitter location for ultra-wideband, transmitted-reference CDMA communication system

• US 7,269,427 B2
• Filed: 10/09/2001
• Issued: 09/11/2007
• Est. Priority Date: 10/09/2001
• Status: Expired due to Fees

• Current Assignee: General Electric Company
• Original Assignee: General Electric Company
• Inventors: Hershey, John Erik, Van Stralen, Nick Andrew, Hoctor, Ralph Thomas, Tomlinson, Harold Woodruff Jr.
• Primary Examiner(s): ZEWDU, MELESS NMN
• Application Number:
  US09/973,140
• Publication Number:
  US 20030069025A1
• Time in Patent Office: 2,163 Days
• Field of Search: 4554561-4566, 455/452, 455457-458, 455/404, 455/422, 455432-433, 455/435.1, 455440-442, 455/403, 455/404.2, 455/70, 455/524, 455/550.1, 455/556.2, 455560-561, 455/67.16, 455/90.1, 455/91, 455/95, 455/115.1, 340/573.4, 340/572.4, 340/473.3
• US Class Current: 455/456.2
• CPC Class Codes: G01S 5/06 Position of source determined by co-ordinating a plurality of position lines defined by path-difference measurements G01S5/12 takes precedence
• CPC Class Codes: H04B 1/7163 using impulse radio

Abstract

A system and method involve tracking the location of objects within an area of interest using transmitted-reference ultra-wideband (TR-UWB) signals. The system includes at least three base stations communicating with a central processor, at least one mobile device and at least one fixed beacon transmitter of known location. The mobile device is equipped with a transmitter for transmitting a TR-UWB signal to a base station, which then determines a location of the mobile device based on time difference of arrival information between the beacon transmitters and mobile devices measured at all the base stations. Preferably, the area of interest includes a plurality of mobile devices each transmitting a delay-hopped TR-UWB signal according to a code-division multiple access scheme. The mobile devices may be attached to a patient and/or a medical asset within the hospital for tracking purposes. Additionally, patient medical information may be transmitted with the TR-UWB signals to allow patient monitoring to occur simultaneously with asset/patient tracking.

Claims

1. A method for determining a location of an object within an area of interest, comprising:

transmitting an RF signal from the object to at least three receivers;

transmitting a signal from a beacon transmitter to the at least three receivers, said beacon transmitters being at a known location, and having an independent local clock;

calculating, at each of the at least three receivers, a plurality of time differences of arrival data based on the signal from said beacon transmitter and the RF signal transmitted from the object; and

determining a location of the object within said area of interest based on said time differences of arrival data from said at least three receivers.

2. The method of claim 1, wherein said RF signal comprises a ultra-wideband signal.

3. The method of claim 2, wherein said ultra-wideband signal comprises a transmitted-reference ultra-wideband signal.

4. The method of claim 2, wherein said ultra-wideband signal comprises a transmitted-reference, delayed hopped ultra-wideband signal;

and wherein the step of transmitting a transmitted-reference, delayed hopped ultra-wideband signal comprises generating pairs of pulses separated by a time interval D and encoding by relative polarity of pulses of said pairs; and

wherein the step of calculating time difference of arrival information comprises delaying received signals by the time interval D.

5. The method of claim 4, wherein the step of transmitting further comprises generating the pairs of pulses at a pulse repetition rate which is variable in order to shape a spectrum of transmission.

6. The method of claim 4, wherein transmitted-reference, delayed hopped ultra-wideband signals are transmitted from a plurality of objects, each transmitted-reference, delayed hopped ultra-wideband signal having a different time interval D between pulses of said pairs.

7. The method of claim 6, wherein the step of transmitting the ultra-wideband signal further includes transmitting medical information of said patient with the ultra-wideband signal.

8. The method of claim 2, wherein the step of transmitting the ultra-wideband signal is performed by a transmitter carried by a patient, and wherein said area of interest is a medical facility.

9. The method of claim 2, wherein the step of transmitting the ultra-wideband signal is performed by a transmitter attached to medical equipment, and wherein said area of interest is a medical facility.

10. The method of claim 1, wherein the step of determining a location of the object comprises using a maximum likelihood algorithm.

11. The method of claim 1, wherein the step of determining the location of the object comprises using a maximum likelihood algorithm.