Timing systems

• US 6,650,597 B2
• Filed: 01/10/2003
• Issued: 11/18/2003
• Est. Priority Date: 02/16/2000
• Status: Expired due to Fees

• Current Assignee: ROKE Manor Research Limited (Chemring Group PLC)
• Original Assignee: ROKE Manor Research Limited (Chemring Group PLC)
• Inventors: Weedon, Robert John, Stribley, Keith Roland
• Primary Examiner(s): Miska, Vit
• Application Number:
  US10/203,884
• Publication Number:
  US 20030156498A1
• Time in Patent Office: 312 Days
• Field of Search: 368/10, 368/46, 368/47, 342/352, 342/357.06, 342/357.13, 701/213-215
• US Class Current: 368/47
• CPC Class Codes: G01S 19/14 specially adapted for specific applications
• CPC Class Codes: G01S 19/39 the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO

Abstract

A time interval measurement system for the timing between events occurring at two spaced apart locations comprising at each location a dual frequency Global Positioning System (GPS) receiver having operatively associated with it a GPS antenna, wherein both the GPS receiver and the antenna are dual frequency (L1, L2) and the former is capable of both Coarse Acquisition (C/A) Code and carrier phase measurements, an accurate frequency reference source giving local time, a data-logger for logging the GPS data, a Time Interval Counter (TIC) means is used to measure the time of a local event relative to the local time and further comprising a central processor system (CPS) and a communication system via which the logged GPS data and time interval data are received at the CPS from each location, the CPS being arranged to derive a time-offset figure, in accordance with a predetermined algorithm which is indicative of the difference between times as measured in dependence upon the frequency reference sources at the two locations.

Claims

1. A time interval measurement system for the timing between events occurring at two spaced apart locations comprising at each location a dual frequency Global Positioning System (GPS) receiver having operatively associated with it a GPS antenna, wherein both the GPS receiver and the antenna are dual frequency (L1, L2) and the former is capable of both Coarse Acquisition (C/A) Code and carrier phase measurements, an accurate frequency reference source giving local time, a data-logger for logging the GPS data, a Time Interval Counter (TIC) means is used to measure the time of a local event relative to the local time and further comprising a central processor system (CPS) and a communication system via which the logged GPS data and time interval data are received at the CPS from each location, the CPS being arranged to derive a time-offset figure, in accordance with a predetermined algorithm which is indicative of the difference between times as measured in dependence upon the frequency reference sources at the two locations.

2. A system as claimed in claim 1, wherein the frequency reference source is integral with the GPS receiver.

3. A system as claimed in claim 1, wherein the GPS receiver is adapted to receive a clock signal from an external source.

4. A system as claimed in claim 1, wherein the frequency reference comprises a quartz crystal oscillator or a rubidium oscillator.

5. A system as claimed in claim 1, wherein the dual frequency GPS antenna has calibrated group delay characteristics with temperature.

6. A system as claimed in claim 1, wherein the antenna comprises a passive dual-band patch with a short cable run removing the need for amplifiers or filters which might give unpredictable temperature characteristics.

7. A system as claimed in claim 1, the data logger comprises a PC.

8. A system as claimed in claim 1, wherein the CPS is co-located with one of the GPS receivers.

9. A system, as claimed in claim 1, used to measure the time difference between reception of pulses, transmitted from an aircraft and received at several spaced apart locations, from which the height of the aircraft can be established.