Frequency coherence within a location network

• US 20070041427A1
• Filed: 08/16/2006
• Published: 02/22/2007
• Est. Priority Date: 11/02/2001
• Status: Active Grant

• Current Assignee: David Small
• Original Assignee: David Small
• Inventors: Small, David
• Granted Patent: US 7,848,397 B2
• Time in Patent Office: Days
• US Class Current: 375/145
• CPC Class Codes: G01S 1/24 the synchronised signals being pulses or equivalent modulations on carrier waves and the transit times being compared by measuring the difference in arrival time of a significant part of the modulations , e.g. LORAN systems
• CPC Class Codes: G01S 19/10 providing dedicated supplementary positioning signals
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/256 relating to timing, e.g. time of week, code phase, timing offset
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 5/0081 Transmission between base stations
• CPC Class Codes: G01S 5/021 Calibration, monitoring or correction G01S5/0252 takes precedence
• CPC Class Codes: G01S 5/0226 Transmitters
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location
• CPC Class Codes: G01S 5/145 Using a supplementary range measurement, e.g. based on pseudo-range measurements
• CPC Class Codes: H04W 56/0015 one node acting as a reference for the others
• CPC Class Codes: H04W 56/0065 using measurement of signal travel time

Abstract

The present invention discloses a system and method of generating frequency coherence between a received reference positioning signal transmitted by at least one reference transmitter and a unique positioning signal generated by a positioning-unit device. A positioning-unit device is a specialized transceiver capable of receiving and interpreting reference positioning signals from the reference transmitter, another positioning-unit device or both. The positioning-unit device receives a reference positioning signal and measures a frequency offset in the received reference positioning signal relative to a common oscillator. Once a frequency offset is measured, the positioning-unit device adjusts a frequency steerable clock by an amount derived from the measured frequency offset. The positioning-unit device then generates a unique positioning signal, which is aligned with the frequency steerable clock. Furthermore, the positioning-unit device continuously adjusts said unique positioning signal by applying the measured frequency offset to the frequency steerable clock, which is referenced to the common oscillator. Subsequently, the frequency of the adjusted unique positioning signal is aligned with the frequency of the received reference positioning signal.

Claims

1. A method of generating frequency coherence between a received reference positioning signal transmitted by at least one reference transmitter and a unique positioning signal generated by a positioning-unit device, said method comprising the steps of:

a) receiving said reference positioning signal;

b) measuring the frequency offset of said received reference positioning signal relative to a common oscillator;

c) adjusting a frequency steerable clock by an amount derived from said measured frequency offset (b);

d) generating said unique positioning signal, wherein said unique positioning signal is aligned with said frequency steerable clock;

e) continuously adjusting said unique positioning signal by applying said measured frequency offset (b) to said frequency steerable clock, said frequency steerable clock referenced to said common oscillator;

such that the frequency of said adjusted unique positioning signal is aligned with the frequency of said reference positioning signal.

2. A method of generating frequency coherence according to claim 1, wherein said frequency steerable clock is adjusted in step (c) by an amount equivalent to said measured frequency offset (b).

3. A method of generating frequency coherence according to claim 1, wherein said adjusted positioning unique signal is transmitted.

4. A method according to claim 1, wherein said adjusted unique positioning signal (e) functions as a reference positioning signal for other positioning-unit devices.

5. A method of generating frequency coherence according to claim 1, wherein said method further comprises the step of adjusting said frequency steerable clock by applying an additional frequency offset for a predetermined time period to time slew said unique positioning signal.

6. A method according to claim 1, wherein said at least one reference transmitter includes positioning-unit devices, Wide Area Augmentation System satellites, Global Navigation Satellite System satellites, Pseudolites, or any other devices that incorporate timing information.

7. A positioning-unit device for generating frequency coherence between a received reference positioning signal transmitted by at least one reference transmitter and a unique positioning signal generated by said positioning-unit device, said positioning-unit device comprising:

a) means for receiving said reference positioning signal;

b) means for measuring a frequency offset in said received reference positioning signal relative to a common oscillator;

c) means for adjusting a frequency steerable clock by an amount derived from said measured frequency offset (b);

d) means for generating said unique positioning signal, wherein said unique positioning signal is aligned with said frequency steerable clock;

e) means for continuously adjusting said unique positioning signal by applying said measured frequency offset (b) to said frequency steerable clock, said frequency steerable clock referenced to said common oscillator;

such that the frequency of said adjusted unique positioning signal is aligned with the frequency of said reference positioning signal.

8. A positioning-unit device according to claim 7, wherein said frequency steerable clock is adjusted in step (c) by an amount equivalent to said measured frequency offset (b).

9. A positioning-unit device according to claim 7, wherein said adjusted unique positioning signal is transmitted.

10. A positioning-unit device according to claim 7, wherein said adjusted unique positioning signal (e) functions as a reference positioning signal for other positioning-unit devices.

11. A positioning-unit device according to claim 7, wherein said frequency steerable clock further comprises means for adjusting said frequency steerable clock by applying an additional frequency offset for a predetermined time period to time slew said unique positioning signal.

12. A positioning-unit device according to claim 7, wherein said at least one reference transmitter includes positioning-unit devices, Wide Area Augmentation System satellites, Global Navigation Satellite System satellites, Pseudolites, or any other devices that incorporate timing information.