Short range radio locator system

• US 5,589,838 A
• Filed: 08/03/1995
• Issued: 12/31/1996
• Est. Priority Date: 09/06/1994
• Status: Expired due to Term

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Regents of the University of California (University of California)
• Inventors: McEwan, Thomas E.
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): PHAN, DAO LINDA
• Application Number:
  US08/510,979
• Time in Patent Office: 516 Days
• Field of Search: 342/457, 342/465, 342/463, 342/387
• US Class Current: 342/387
• CPC Class Codes: G01F 23/284 Electromagnetic waves
• CPC Class Codes: G01S 1/045 Receivers
• CPC Class Codes: G01S 11/02 using radio waves G01S19/00 takes precedence
• CPC Class Codes: G01S 13/003 Bistatic radar systems; Multistatic radar systems
• CPC Class Codes: G01S 13/0209 Systems with very large relative bandwidth, i.e. larger than 10 %, e.g. baseband, pulse, carrier-free, ultrawideband
• CPC Class Codes: G01S 13/0218 Very long range radars, e.g. surface wave radar, over-the-horizon or ionospheric propagation systems for meteorological use G01S13/95
• CPC Class Codes: G01S 13/04 Systems determining presence of a target based on relative movement of target G01S13/56
• CPC Class Codes: G01S 13/103 particularities of the measurement of the distance G01S13/12, G01S13/14, G01S13/16, G01S13/18 and G01S13/20 take precedence
• CPC Class Codes: G01S 13/106 using transmission of pulses having some particular characteristics G01S13/12, G01S13/22, G01S13/24, G01S13/26, G01S13/28 and G01S13/30 take precedence
• CPC Class Codes: G01S 13/18 wherein range gates are used
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 2013/9314 Parking operations
• CPC Class Codes: G01S 2013/9321 Velocity regulation, e.g. cruise control
• 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: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01S 7/285 Receivers
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• CPC Class Codes: G08G 1/04 using optical or ultrasonic detectors
• CPC Class Codes: H04B 1/7163 using impulse radio

Abstract

A radio location system comprises a wireless transmitter that outputs two megahertz period bursts of two gigahertz radar carrier signals. A receiver system determines the position of the transmitter by the relative arrival of the radar bursts at several component receivers set up to have a favorable geometry and each one having a known location. One receiver provides a synchronizing gating pulse to itself and all the other receivers to sample the ether for the radar pulse. The rate of the synchronizing gating pulse is slightly offset from the rate of the radar bursts themselves, so that each sample collects one finely-detailed piece of information about the time-of-flight of the radar pulse to each receiver each pulse period. Thousands of sequential pulse periods provide corresponding thousand of pieces of information about the time-of-flight of the radar pulse to each receiver, in expanded, not real time. Therefore the signal processing can be done with relatively low-frequency, inexpensive components. A conventional microcomputer is then used to find the position of the transmitter by geometric triangulation based on the relative time-of-flight information.

Claims

1. A radio location system, comprising:

a roving transmitter with an unknown position and providing for periodic bursts of wireless radio frequency (RF) carrier transmissions at a first repetition rate;

a plurality of receivers with known locations and providing for the reception of said bursts of RF carrier transmissions according to a sample gate input for each;

local oscillator generation means connected to provide a single sample gate signal to each of said sample gate inputs at a second repetition rate that is different than said first repetition rate, wherein said first and second repetition rates are in phase once each "n" cycles of said first repetition rate;

digital output means connected to each of the receivers for binary signaling TRUE/FALSE of whether the reception of one of said bursts of said RF carrier transmissions arrived simultaneously with one of said sample gate signals; and

computer means for storing representations which of the plurality of receivers and what particular cycles "0 . . . n" of said first repetition rate provided a TRUE binary signal connected from the digital output means, and for computing a relative difference in the time-of-flight of said RF carrier transmissions to each of the plurality of receivers from said stored representations, and for computing a position estimate of the roving transmitter from said relative difference and said known positions of each of the plurality of receivers.

2. The system of claim 1, wherein:

the roving transmitter comprises a crystal oscillator that modulates a microwave radio frequency output stage.

3. The system of claim 1, further comprising:

local oscillator generation means connected to provide a single sample gate signal to each of said sample gate inputs at a second repetition rate that is different than said first repetition rate, wherein said first and second repetition rates are in phase once each "n" cycles of said first repetition rate.

4. The system of claim 1, further comprising:

digital output means connected to each of the receivers for binary signaling TRUE/FALSE of whether the reception of one of said bursts of said RF carrier transmissions arrived simultaneously with one of said sample gate signals.

5. The system of claim 1, further comprising:

computer means for storing representations which of the plurality of receivers and what particular cycles "0 . . . n" of said first repetition rate provided a TRUE binary signal connected from the digital output means, and for computing a relative difference in the time-of-flight of said RF carrier transmissions to each of the plurality of receivers from said stored representations, and for computing a position estimate of the roving transmitter from said relative difference and said known positions of each of the plurality of receivers.