Method and apparatus for measuring distance

• US 7,808,424 B2
• Filed: 10/13/2009
• Issued: 10/05/2010
• 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:
  US12/577,796
• Publication Number:
  US 20100026557A1
• Time in Patent Office: 357 Days
• Field of Search: 342/118
• 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. The durations of the two codes may be 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 device suitable for use in use in a system for measuring distance, comprising means for generating and 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, and 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.

2. The device 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 device as claimed in claim 1, wherein the means for generating and transmitting the signal comprising simultaneous first and second components further comprises means for multiplying the first component by an in-phase local oscillator signal, means for multiplying the second component by a quadrature-phase local oscillator signal, and means for summing the resulting products.

4. The device 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.