Position location system and method

• US 6,259,404 B1
• Filed: 03/15/1999
• Issued: 07/10/2001
• Est. Priority Date: 12/15/1995
• Status: Expired due to Fees

• Current Assignee: Signatron Technology Corporation
• Original Assignee: Signatron Technology Corporation
• Inventors: Bussgang, Julian, Zagami, James M., Weitzen, Jay, Parl, Steen A.
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/268,179
• Time in Patent Office: 848 Days
• Field of Search: 342/457, 342/465, 342/463
• US Class Current: 342/457
• CPC Class Codes: G01S 1/045 Receivers
• 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

Abstract

A position location system includes multiple base stations spaced over a region. A remote unit within the region transmits a locating signal which is received by the base stations. The base stations report amplitude, phase and time data related to the locating signal to a control station. The control station includes a processor and memory that combine the data from all of the participating base stations to directly compute an optimal estimate of the location of the portable unit. The control station generates a locator function based upon the probability that the portable unit is located at a particular position. By optimizing the locator function, the error in the computation is minimized to produce an accurate position estimate.

Claims

1. A position location system comprising:

a transmitting unit comprising a transmitter that transmits a locating signal composed of multiple tones;

at least three antennas located at at least two base stations which receive the locating signal;

at least one receiver coupled to each antenna that generates representative complex signals indicative of amplitude and phase of at least two selected tone components of the locating signal as received at the corresponding antenna, the receiver also generating values indicative of the frequencies of received tone components; and

a processor that receives the representative complex signals from the antenna and uses the amplitude and phase information in said representative complex signals and the generated frequency values to define a locator function for the transmitting unit, and determines estimated location coordinates for the transmitting unit that generate a maximum value of the locator function.

2. The position location system of claim 1 wherein the processor uses the received values indicative of the frequencies to eliminate frequency offsets of the transmitting unit to estimate location more accurately.

3. The position location system of claim 1 wherein the processor uses the received values indicative of the frequencies to estimate both motion and velocity of the transmitting unit.