Method and apparatus for measuring distance using low clock rate signal

• US 7,518,546 B2
• Filed: 03/08/2006
• Issued: 04/14/2009
• Est. Priority Date: 03/25/2005
• Status: Active Grant

• Current Assignee: Institute of Radio Engineering and Electronics, Samsung Electronics Co. Ltd.
• Original Assignee: Institute of Radio Engineering and Electronics, Samsung Electronics Co. Ltd.
• Inventors: Alexander, Dmitriev S., Yuri, Andreyev V., Kim, Jae-hyon, Kim, Young-hwan, Lee, Seong-soo
• Primary Examiner(s): Tarcza; Thomas H
• Assistant Examiner(s): Barker; Matthew M
• Application Number:
  US11/369,724
• Publication Number:
  US 20060214840A1
• Time in Patent Office: 1,133 Days
• Field of Search: 342/118
• US Class Current: 342/118
• CPC Class Codes: G01S 13/76 wherein pulse-type signals are transmitted

Abstract

Provided is an apparatus and a method of measuring a distance between devices using a low clock frequency signal. The apparatus includes clock frequency generators, counters, a controller and a calculator for determining the distance based on clock signal overlap. Radio waves are transmitted and a number of clocks of a clock signal having a clock frequency b are counted, and if the transmitted radio waves are received again, a number of clocks of a clock signal having a clock frequency a are counted. If the clock signals having the clock frequencies a and b overlap with each other, counting of the numbers of the clocks of the clock signals having the frequencies b and a stops, and the distance is measured using the count values of the clock signals having the clock frequencies a and b. As a result, number of clocks of clock signals having low clock frequencies with a uniform difference can be counted to precisely measure a distance.

Claims

1. A method of measuring a distance, comprising:

transmitting predetermined radio waves;

generating a first clock signal having a clock frequency b and counting N3 a number of clocks of the first clock signal;

generating a second clock signal having a clock frequency a and delaying the second clock signal until the transmitted radio waves are received to generate a delayed second clock signal;

counting N1 a number of clocks of the delayed second clock signal having the clock frequency a; and

measuring the distance using the count values N1, N3 of the clock signals having the clock frequencies a and b,

stopping the counting of N1 and N3 when the first clock signal and the delayed second clock signal overlap,

counting N2 a number of overlaps between the first clock signal and the delayed second clock signal; and

measuring the distance using the counts N1, N2, and N3.

2. The method of claim 1, wherein a clock frequency of the clock signal having the clock frequency b is higher than a clock frequency of the clock signal having the clock frequency a.

3. The method of claim 2, wherein the clock frequencies of both clock frequency a and clock frequency b are greater than the difference between clock frequency a and clock frequency b.

4. The method of claim 1, wherein a time T_xwhen the transmitted radio waves are received again is calculated using Equation as follows:

$T_x=\frac{N<br><br><br><br>3+0.5\times <br><br>N<br><br><br><br>2}{b}-\frac{N<br><br><br><br>1+0.5\times <br><br>N<br><br><br><br>2}{a}.$

5. The method of claim 4, wherein the device calculates the distance S using Equation as follows:

S=0.5c×

(T_x−

τ

₀)

wherein c denotes a light speed, and τ

₀ denotes a time required for re-transmitting the radio waves received by a receiver device.

6. The method of claim 1, wherein overlaps are determined to occur when a combined energy of the first clock signal and the delayed second clock signal exceeds a predetermined value.

7. An apparatus for measuring a distance between devices, comprising:

a clock signal generator that generates a first clock signal having a clock frequency b and a second clock signal having a clock frequency a;

a first counter that transmits radio waves of the first clock signal and counts N3 a number of clocks of the first clock signal;

a delayer that delays a second clock signal having a clock frequency a;

a second counter that counts N1 a number of clocks of the second clock signal delayed by the delayer;

a controller that determines when the transmitted radio waves are received and instructs the second counter to count the clocks of the second clock signal delayed;

a calculator that calculates the distance between devices using count N1 and count N3; and

a third counter that counts N2 a number of overlaps between the first clock signal and the second clock signal delayed by the delayer,

wherein the controller stops the counting of N1 and N3 when the first clock signal and the second clock signal delayed overlap,

wherein the distance is measured using N1, N2, and N3.

8. The apparatus of claim 7, wherein the clock frequency b is higher than the clock frequency a.

9. The apparatus of claim 8, wherein the clock frequencies of both the clock frequency a and the clock frequency b are greater than the difference between the clock frequency a and the clock frequency b.

10. The apparatus of claim 7, wherein the calculator calculates a time T_x when the transmitted radio waves are received again using Equation as follows:

$T_x=\frac{N<br><br><br><br>3+0.5\times <br><br>N<br><br><br><br>2}{b}-\frac{N<br><br><br><br>1+0.5\times <br><br>N<br><br><br><br>2}{a}.$

11. The apparatus of claim 10, wherein the calculator calculates the distance S using Equation as follows:

S=0.5c×

(T_x−

τ

₀)

wherein c denotes a light speed, and τ

₀ denotes a time required for re-transmitting the radio waves received by a receiver device.

12. The apparatus of claim 7, wherein overlaps are determined to occur when a combined energy of the first clock signal and the delayed second clock signal exceeds a predetermined value.