SYSTEM AND METHOD TO POSITION REGISTER AND PHASE SYNCHRONIZE A MONITORING NETWORK

• US 20090027272A1
• Filed: 07/25/2007
• Published: 01/29/2009
• Est. Priority Date: 07/25/2007
• Status: Active Grant

• Current Assignee: Information Systems Laboratories, Inc.
• Original Assignee: Information Systems Laboratories, Inc.
• Inventors: Don Carlos, John
• Granted Patent: US 7,663,535 B2
• Time in Patent Office: Days
• US Class Current: 342/442
• CPC Class Codes: G01C 21/206 specially adapted for indoor navigation
• CPC Class Codes: G01S 13/87 Combinations of radar systems, e.g. primary radar and secondary radar
• CPC Class Codes: G01S 5/02213 Receivers arranged in a network for determining the position of a transmitter
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 7/403 in azimuth, i.e. in the horizontal plane
• CPC Class Codes: G01S 7/4034 in elevation, i.e. in the vertical plane
• CPC Class Codes: G01S 7/4082 using externally generated reference signals, e.g. via remote reflector or transponder

Abstract

A system is disclosed for position registration and phase synchronization of monitors in a monitor network. Each monitor includes a transceiver having a transponder circuit with a calibrated transponder delay. To measure a distance between monitors, an oscillator at a first monitor generates a measurement signal which is transponded by a second monitor for receipt by the first monitor. A phase difference between the received signal and the first monitor oscillator is determined and used with the signal velocity and transponder delay to calculate the distance between monitors. The measured distances are combined with other data (e.g. monitor elevations) to calculate monitor locations. A phase delay is then measured by transmitting a signal from the first to the second monitor for comparison with the second monitor oscillator. A phase difference between oscillators (for use in synchronizing the monitors) is then calculated using the phase delay, separation distance and signal velocity.

Claims

1. A system for establishing position registration and pair-wise phase differences for a plurality of monitors in a monitor network, to prepare said monitor network for locating a beacon, said system comprising:

a means at a first said monitor for transmitting a measurement signal from said first monitor to a second said monitor with known phase and signal propagation velocity;

a means at said second monitor for transponding the measurement signal with a pre-identified transponder delay duration for transmission as a return signal from said second monitor to said first monitor;

a means for comparing the return signal with the transmitted signal to establish a phase difference;

a means for determining a separation distance between said first monitor and said second monitor using said established phase difference, said propagation velocity and said pre-identified transponder delay duration to register said first monitor relative to said second monitor; and

a means at one of said first/second monitor for using said separation distance and a measurement signal from said other second/first monitor to determine a pair-wise phase difference for said first and second monitors.

2. A system as recited in claim 1 further comprising a means modifying one of said first and second monitors to eliminate said pair-wise phase difference between said first and second monitors and synchronize said first and second monitors.

3. A system as recited in claim 1 further comprising:

a means for determining separation distances between a third said monitor in said network and said first and second monitors;

a means for determining separation distances between a fourth said monitor in said network and said first, second and third monitors; and

a plurality of elevation measurement instruments, with each elevation measurement instrument being collocated with a respective said monitor in said network to determine an elevation for each said monitor, said monitor elevations for use with said separation distances to register the positions of said monitors in said network.

4. A system as recited in claim 1 further comprising a means collocated with said first monitor for determining an elevation angle to said second monitor, an elevation angle to a third monitor in said network and an azimuthal angle between said second and third monitors, said angles for use in position registering said monitors.

5. A system as recited in claim 4 wherein said means for determining said angles comprises a theodolite.

6. A system as recited in claim 5 wherein said system further comprises a first retroreflector collocated with said second monitor for reflecting signals from said theodolite and a second retroreflector collocated with said third monitor for reflecting signals from said theodolite.

7. A system as recited in claim 1 wherein said measurement signal has a frequency in the range of approximately 1 MHz to approximately 3 MHz.

8. A system as recited in claim 1 wherein said transmitting means comprises an oscillator.

9. A system for registering the positions of oscillators in a network of common frequency oscillators and determining pair-wise phase differences between pairs of oscillators in said network to prepare said network for use in locating a beacon, said system comprising:

a means collocated with a first said oscillator in said network for transmitting measurement signals, said measurement signals being transmitted substantially in phase with said first oscillator, said transmitted signal having a signal propagation velocity;

a means collocated with said second oscillator for transponding a said measurement signal, said transponding means having a pre-identified transponder delay duration;

a means collocated with said first oscillator for receiving said transponded signal and comparing said received transponded signal with said first oscillator to establish a first phase delay;

a means for determining a separation distance between said first oscillator and said second oscillator using said established first phase delay, said propagation velocity and said pre-identified transponder delay duration, said separation distance for position registering said first oscillator relative to said second oscillator;

a means collocated with said second oscillator for receiving a said measurement signal and comparing said received signal with said second oscillator to establish a second phase delay; and

a means for determining a pair-wise phase difference between said first and second oscillators using said second phase delay, said propagation velocity and said separation distance.

10. A system as recited in claim 9 further comprising a means for modifying one of said first and second oscillators to eliminate said pair-wise phase difference between said first and second oscillators and synchronize said first and second oscillators.

11. A system as recited in claim 9 further comprising a plurality of elevation measurement instruments, with each elevation measurement instrument being collocated with a respective said oscillator in said network to determine an elevation for each said oscillator, said oscillator elevation for use in registering the positions of said oscillators in said network.

12. A system as recited in claim 9 further comprising a means collocated with said first oscillator for determining an azimuthal angle and an elevation angle to said second oscillator and an azimuthal angle and an elevation angle to a third oscillator in said network, said angle for use in position registering said oscillators.

13. A system as recited in claim 12 wherein said means for determining said angles comprises a theodolite and wherein said system further comprises a first retroreflector collocated with said second oscillator for reflecting signals from said theodolite and a second retroreflector collocated with said third oscillator for reflecting signals from said theodolite.

14. A system as recited in claim 9 wherein said measurement signal has a frequency in the range of approximately 1 MHz to approximately 3 MHz.

15. A method for registering the positions of oscillators in a network of common frequency oscillators and determining pair-wise phase differences between pairs of oscillators in said network to prepare said network for use in locating a beacon, said method comprising the steps of:

transmitting a first measurement signal from the position of a first said oscillator, said first measurement signal being transmitted substantially in phase with said first oscillator and having a signal propagation velocity;

transponding said first measurement signal at the position of a second said oscillator with a pre-identified transponder delay duration;

receiving said transponded signal at the position of said first oscillator and comparing said received transponded signal with said first oscillator to establish a first phase delay;

determining a separation distance between said first oscillator and said second oscillator using said established first phase delay, said propagation velocity of said first measurement signal and said pre-identified transponder delay. duration, said separation distance for position registering said first oscillator relative to said second oscillator;

transmitting a second measurement signal from the position of a first said oscillator, said second measurement signal being transmitted substantially in phase with said first oscillator and having a signal propagation velocity;

receiving said second measurement signal at the position of said second oscillator;

comparing said received signal with said second oscillator to establish a second phase delay; and

determining a pair-wise phase difference between said first and second oscillators using said second phase delay, said propagation velocity of said second measurement signal and said separation distance.

16. A method as recited in claim 15 further comprising the step of modifying one of said first and second oscillators to eliminate said pair-wise phase difference between said first and second oscillators and synchronize said first and second oscillators.

17. A method as recited in claim 15 further comprising the steps of:

providing a plurality of elevation measurement instruments;

collocating a said elevation measurement instrument with each said oscillator in said network; and

using each said elevation measurement instrument to determine an elevation for each said oscillator, said oscillator elevations for use in registering the positions of said oscillators in said network.

18. A method as recited in claim 15 further comprising the steps of:

measuring a first elevation angle from said first oscillator to said second oscillator;

measuring a first azimuth angle, said first azimuth angle measured from said first oscillator between a reference line and said second oscillator;

measuring a second elevation angle from said first oscillator to a third oscillator in said network;

measuring a second azimuth angle, said second azimuth angle measured from said first oscillator between said reference line and said third oscillator; and

using said first and second elevation angles and said first and second azimuth angles with said separation distance to position register said oscillators.

19. A method as recited in claim 15 wherein said measuring steps are accomplished using a theodolite.

20. A method as recited in claim 15 wherein said first measurement signal has a frequency in the range of approximately 1 MHz to approximately 3 MHz and said second measurement signal has a frequency in the range of approximately 1 MHz to approximately 3 MHz.