High-resolution, active reflector radio frequency ranging system

• US 9,250,321 B2
• Filed: 04/29/2014
• Issued: 02/02/2016
• Est. Priority Date: 04/30/2009
• Status: Active Grant

• Current Assignee: Alps Alpine Co., Ltd.
• Original Assignee: Greina Technologies, Inc. (Alps Alpine Co., Ltd.)
• Inventors: Lee, Daniel Joseph
• Primary Examiner(s): Sotomayor, John B
• Application Number:
  US14/265,072
• Publication Number:
  US 20140232588A1
• Time in Patent Office: 644 Days
• Field of Search: 342/125, 342/98, 342/100, 342/102, 342/103, 342/175, 342/194
• US Class Current: 1/1
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement
• CPC Class Codes: G01S 5/0289 of multiple transceivers, e.g. in ad hoc networks
• CPC Class Codes: H04B 2201/70715 with application-specific features

Abstract

A radio frequency ranging system is grounded in establishing and maintaining phase and frequency coherency of signals received by a slave unit from a master unit and retransmitted to the master unit by the slave unit. For a preferred embodiment of the invention, coherency is established through the use of a delta-sigma phase-lock loop, and maintained through the use, on both master and slave units, of thermally-insulated reference oscillators, which are highly stable over the short periods of time during which communications occur. A phase relationship counter is employed to keep track of the fractional time frames of the phase-lock loop as a function of the reference oscillator, thereby providing absolute phase information for an incoming burst on any channel, thereby enabling the system to almost instantaneously establish or reestablish the phase relationship of the local oscillator so that it synchronized with the reference oscillator.

Claims

1. A ranging system for determining a ranging measurement, the ranging system comprising:

a first unit that transmits at least one signal on at least one carrier asking for the ranging measurement, the at least one signal including at least one read range data packet;

a second unit that receives the at least one signal, wherein the second unit achieves commonality of three frequencies and phase coherence with the at least one signal, the second unit including;

a first oscillator used in receiving the at least one signal and transmitting at least one second signal back to the second unit;

a reference oscillator that controls the first oscillator, wherein the at least one read range data packet is used to achieve the commonality of three frequencies and phase coherence in the reference oscillator; and

a phase coherency counter, wherein the phase coherency counter enables the second unit to transmit the at least one second signal back to the first unit with a predictable phase; and

wherein the first unit receives the at least one second signal and determines the ranging measurement between the first unit and the second unit.

2. The ranging system of claim 1, wherein the first unit comprises:

a first oscillator used in transmitting the at least one signal and receiving the at least one second signal;

a reference oscillator that provides three frequencies and phase for the ranging measurement; and

a phase coherency counter to switch the first unit between transmit and receive with a predictable phase, wherein the phase coherency counter provides phase information relationships of the first oscillator of the first unit.

3. The ranging system of claim 1, wherein the phase coherency counter of the second unit provides phase information relationships of all frequencies of the first oscillator.

4. The ranging system of claim 3, wherein the phase coherency counter comprises:

a single phase lock loop that combines input from a phase relationship counter and a frequency setting of the first oscillator to generate the predictable phase in the first oscillator.

5. The ranging system of claim 4, wherein the first unit measures a phase difference of the at least one second signal from the predictable phase in determining the ranging measurement.

6. The ranging system of claim 1, wherein the reference oscillator comprises a thermally-insulated reference oscillator.

7. The ranging system of claim 1, wherein each signal included in the at least one signal are transmitted at different times.

8. The ranging system of claim 7, wherein the at least one signal includes a first signal at a first frequency, a second signal at a second frequency, and a third signal at a third frequency to initially determine the ranging measurement, wherein at least one of the first unit and the second unit hops between the first, second, and third frequency to determine an absolute distance between the first unit and the second unit.

9. The ranging system of claim 8, wherein the first unit uses phase relationships among the first, second, and third signal to identify a multi-path data, wherein the first unit eliminates the multi-path data using at least one signal at a different frequency.

10. The ranging system of claim 8, wherein the first, second, and third frequencies are selected to avoid ambiguous ranging measurements.

11. The ranging system of claim 1, wherein the predictable phase identifies a phase relationship at the second unit between the at least one signal received by the second unit and the at least one second signal transmitted by the second unit.

12. The ranging system of claim 11, wherein the at least one signal transmitted by the first unit and the at least one second signal transmitted by the second unit have one of:

the same frequencies, different frequencies, or some of the same frequencies.

13. The ranging system of claim 11, wherein at least some of the at least one signal and the at least one second signal can be transmitted at random times.

14. A method for determining a ranging measurement, the method comprising:

transmitting at least one signal from a first unit to a second unit, the at least one signal including read range data packets;

extracting three frequencies and phase information of the at least one signal from the read range data packets;

setting a reference oscillator to match the three frequencies and phase information of the at least one signal;

generating at least one second signal having a predictable phase using the reference oscillator;

transmitting the at least one second signal back to the first unit from the second unit; and

determining the ranging measurement between the first unit and the second unit by a difference between the predictable phase of the at least one second signal at the second unit and a measured phase of the at least one second signal at the first unit.

15. The method of claim 14, wherein transmitting at least one signal further comprises transmitting a first signal at a first frequency, a second signal at a second frequency, and a third signal at a third frequency, wherein the first, second, and third signals are selected to determine an absolute distance of multiple wavelengths.

16. The method of claim 14, wherein multi-path data is identified by transmitting at least three signals at different frequencies, the at least three signals included in the at least one signal.

17. The method of claim 14, wherein extracting frequency and phase information further comprises measuring a phase of the at least one signal.

18. The method of claim 14, wherein setting a reference oscillator further comprises setting the reference oscillator using a processor.

19. The method of claim 14, wherein transmitting at least one signal further comprises hopping between multiple frequencies, wherein each of the at least one signals are transmitted at different times and wherein each of the at least one second signals are transmitted at different times.

20. The method of claim 14, further comprising using the reference oscillator to provide predictable phase relationships between all frequencies of a first oscillator included in the second unit.