Method and apparatus for measuring distance using dual-component radar

• US 7,629,919 B2
• Filed: 11/21/2003
• Issued: 12/08/2009
• Est. Priority Date: 12/11/2002
• Status: Active Grant

• Current Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Wilcox, Martin S.
• Primary Examiner(s): Black; Thomas G
• Assistant Examiner(s): Chen; Shelley
• Application Number:
  US10/537,856
• Publication Number:
  US 20060044181A1
• Time in Patent Office: 2,209 Days
• Field of Search: 342118-146
• US Class Current: 342/118
• CPC Class Codes: G01S 13/765 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/767 Responders; Transponders teaching or practice apparatus for gun-aiming or gun-laying using reflecting targets or active targets F41G3/26
• CPC Class Codes: G01S 13/825 with exchange of information between interrogator and responder
• CPC Class Codes: G01S 13/84 for distance determination by phase measurement

Abstract

A device measures distance using a wireless signal that has two simultaneously transmitted components. Each of the two components includes a respective repeated code, the two codes having different durations. On receipt of the signal, the propagation distance is calculated separately for each code and compared. The calculated distance is considered to be valid only if the two calculations yield the same result. Preferably, the durations of the two codes are proportional to numbers having a relative prime relationship. The signal is generated and transmitted by the same device that performs the distance calculation, with the signal being retransmitted back to the device by a remote device, or may be generated and transmitted by the remote device.

Claims

1. A method of determining a distance between a first device and a second device, comprising,

at the first device,

transmitting a signal comprising simultaneous first and second components, wherein the first component comprises a repeated first code and the second component comprises a repeated second code and the first and second codes are of unequal duration, wherein the first component is frequency or phase modulated onto a carrier forming a direct sequence spread spectrum (DSSS) signal and the second component is amplitude modulated and occupies nulls in the DSSS signal, and

at the second device:

receiving the signal;

detecting the first and second codes;

determining from the detected first and second codes respective first and second indications of the distance;

comparing the first and second indications of the distance;

generating a third indication of the distance in response to the first and second indications of the distance being equal within a predetermined tolerance, and

initiating an alarm if the third indication of the distance is above a predetermined threshold value.

2. The method as claimed in claim 1, wherein the respective durations of the first and second codes are proportional to respective numbers having a relative prime relationship.

3. The method as claimed in claim 1, further comprising transmitting the signal from the second device and at the first device receiving the signal transmitted from the second device, wherein the transmitting at the first device comprises retransmitting the signal received from the second device.

4. The method as claimed in claim 1, wherein at least one of the first and second indications of distance is an indication of time of flight of the signal.

12. The method of claim 1, wherein the repeated first code is generated by a first linear feed-back shift register and has a first length of N1, and the second code is generated by a second linear feed-back shift register and has a second length of N2, and wherein N1=2^M−

1 and N2=2^M+1−

1, M being a number of stages of the first linear feed-back shift register and M+1 being a number of stages of the second linear feed-back shift register.

5. A system for determining distance comprising:

a first device having

means for transmitting a signal comprising simultaneous first and second components, wherein the first component comprises a repeated first code and the second component comprises a repeated second code and the first and second codes are of unequal duration, wherein the first component is frequency or phase modulated onto a carrier forming a direct sequence spread spectrum (DSSS) signal and the second component is amplitude modulated and occupies nulls in the DSSS signal, and

a second device having

means for receiving the signal,

means for detecting the first and second codes, means ror determining from the detected first and second codes respective first and second indications of the distance, means for comparing the first and second indications of the distance, and

means for generating a third indication of the distance in response to the first and second indications of the distance being equal within a predetermined tolerance.

6. The system as claimed in claim 5, wherein the respective durations of the first and second codes are proportional to respective numbers having a relative prime relationship.

7. The system as claimed in claim 5, the second device further comprising means for generating and transmitting the signal, and the first device further comprising means for receiving the signal transmitted by the second device and wherein the means for transmitting is coupled to retransmit the signal received from the second device.

8. The system as claimed in claim 5, wherein at least one of the first and second indications of distance is an indication of time of flight of the signal.

13. The system of claim 5, wherein the repeated first code is generated by a first linear feed-back shift register and has a first length of N1, and the second code is generated by a second linear feed-back shift register and has a second length of N2, and wherein N1=2^M−

1 and N2=2^M+1−

1, M being a number of stages of the first linear feed-back shift register and M+1 being a number of stages of the second linear feed-back shift register.

9. A device for determining distance, comprising:

means for receiving a signal comprising simultaneous first and second components, wherein the first component comprises a repeated first code and the second component comprises a repeated second code and the first and second codes are of unequal duration, wherein the first component is frequency or phase modulated onto a carrier forming a direct sequence spread spectrum (DSSS) signal and the second component is amplitude modulated and occupies nulls in the DSSS signal,

means for detecting the first and second codes,

means for determining from the detected first and second codes respective first and second indications of the propagation distance of the signal,

means for comparing the first and second indications of the propagation distance, and

means for generating a third indication of the propagation distance in response to the first and second indications of the propagation distance being equal within a predetermined tolerance.

10. The device as claimed in claim 9, comprising means for generating and transmitting the signal.

11. The device as claimed in claim 10, wherein the respective durations of the first and second codes are proportional to respective numbers having a relative prime relationship.

14. The device of claim 9, wherein the repeated first code is generated by a first linear feed-back shift register and has a first length of N1, and the second code is generated by a second linear feed-back shift register and has a second length of N2, and wherein N1=2^M−

1 and N2=2^M+1−

1, M being a number of stages of the first linear feed-back shift register and M+1 being a number of stages of the second linear feed-back shift register.