Distance measuring device, distance measuring method and distance measuring program

• US 20070013578A1
• Filed: 07/14/2006
• Published: 01/18/2007
• Est. Priority Date: 07/15/2005
• Status: Active Grant

• Current Assignee: Nohken, Inc., University of Tokushima
• Original Assignee: Nohken, Inc., University of Tokushima
• Inventors: Wakabayashi, Kazuhiro, Iritani, Tadamitsu
• Granted Patent: US 7,479,921 B2
• Time in Patent Office: Days
• US Class Current: 342/118
• CPC Class Codes: G01S 13/36 with phase comparison between the received signal and the contemporaneously transmitted signal
• CPC Class Codes: G01S 7/356 involving particularities of FFT processing

Abstract

A transmission unit emits an electromagnetic wave having the same frequency f as an output signal from a sending unit in a direction of a measurement axis. A detecting unit performs synchronous detection on a reflected wave detected by a directional coupler by an in-phase signal and a quadrature signal of the transmission signal, and by extracting DC component from the detection signal, detects the in-phase component and quadrature component of the reflected wave. An analysis signal generating unit mixes the in-phase component and quadrature component of the reflected wave and signals having periodicity corresponding to a prescribed distance, and using only one of the resulting side bands, generates an analysis signal. Fourier transform unit finds distance to the object of measurement from a profile obtained by Fourier transform of the analysis signal.

Claims

1. A distance measuring device measuring a distance to an object of measurement, comprising:

a sending source outputting a transmission signal having a variable frequency;

a transmission unit generating and emitting to said object of measurement an electromagnetic wave of the same frequency as said transmission signal;

a detecting unit detecting a reflected wave of said electromagnetic wave; and

a signal processing unit calculating a distance to said object of measurement by an operation of a relation between said detected reflected wave and the frequency of said transmission signal;

wherein

said detecting unit includes

wave-detecting means for performing synchronous detection of said detected reflected wave with said transmission signal, to extract a phase change component of said reflected wave; and

said signal processing unit includes

frequency converting means for changing variable frequency of said extracted phase change component by a frequency corresponding to a prescribed distance,

analysis signal generating means for taking, as an analysis signal, one of upper and lower side bands obtained by said frequency converting means, and

Fourier transform means for performing Fourier transform on said analysis signal to calculate a profile, and for finding distance to said object of measurement based on a local maximum of said profile and said prescribed distance.

2. The distance measuring device according to claim 1, wherein

said sending source includes

upward sweeping means for sweeping upward a prescribed transmission frequency with a prescribed bandwidth at a prescribed step, and

downward sweeping means for sweeping downward said prescribed transmission frequency with the prescribed bandwidth at the prescribed step;

said signal processing unit includes

means for holding, as first position information, a distance to said object of measurement obtained by said Fourier transform means through said upward sweeping means, and as second position information, a distance to said object of measurement obtained by said Fourier transform means through said downward sweeping means, and

correcting means for averaging said held first position information and second position information to derive true distance to said object of measurement.

3. The distance measuring device according to claim 1, wherein

said wave-detecting means extracts in-phase component of said phase change component by synchronous detection of said reflected wave with said transmission signal, and extracts quadrature component of said phase change component by synchronous detection of said reflected wave with a signal different in phase by π

/2 from said transmission signal.

4. The distance measuring device according to claim 3, wherein

said prescribed distance is variable in accordance with a number of divisions for sweeping a prescribed transmission frequency with a prescribed bandwidth.

5. The distance measuring device according to claim 4, wherein

said prescribed distance is set, at the largest, to be approximately a half of a maximum detectable distance determined by said prescribed bandwidth and said number of divisions.

6. The distance measuring device according to claim 1, wherein

said wave-detecting means extracts the phase change component of said reflected wave by subtracting DC component of said transmission signal from said reflected wave subjected to envelope detection.

7. A distance measuring method of measuring a distance to an object of measurement, comprising the steps of:

outputting a signal having a variable frequency;

generating and emitting to said object of measurement an electromagnetic wave of the same frequency as said signal;

detecting a reflected wave of said electromagnetic wave; and

calculating a distance to said object of measurement by an operation of a relation between said detected reflected wave and the frequency of said signal;

wherein

said step of detecting a reflected wave includes the step of

extracting a phase change component of said reflected wave by synchronous detection of said detected reflected wave with said signal; and

said step of calculating the distance to said object of measurement includes the steps of

changing variable frequency of said extracted phase change component by a frequency corresponding to a prescribed distance,

taking, as an analysis signal, one of upper and lower side bands obtained by said frequency change, and

performing Fourier transform on said analysis signal to calculate a profile, and finding distance to said object of measurement based on a local maximum of said profile and said prescribed distance.

8. The distance measuring method according to claim 7, wherein

said step of outputting a signal having variable frequency includes the steps of

sweeping upward a prescribed transmission frequency with a prescribed bandwidth at a prescribed step, and

sweeping downward said prescribed transmission frequency with the prescribed bandwidth at the prescribed step;

said step of calculating the distance to said object of measurement further includes the steps of

holding, as first position information, a distance to said object of measurement obtained by said Fourier transform through said upward sweeping, and as second position information, a distance to said object of measurement obtained by said Fourier transform through said downward sweeping, and

averaging said held first position information and second position information to derive true distance to said object of measurement.

9. The distance measuring method according to claim 7, wherein

in said step of extracting phase change component of said reflected wave,

in-phase component of said phase change component is extracted by synchronous detection of said reflected wave with said signal, and quadrature component of said phase change component is extracted by synchronous detection of said reflected wave with a signal different in phase by π

/2 from said signal.

10. The distance measuring method according to claim 9, wherein

said prescribed distance is variable in accordance with a number of divisions for sweeping a prescribed transmission frequency with a prescribed bandwidth.

11. The distance measuring method according to claim 10, wherein

said prescribed distance is set, at the largest, to be approximately a half of a maximum detectable distance determined by said prescribed bandwidth and said number of divisions.

12. The distance measuring method according to claim 7, wherein

in said step of extracting the phase change component of said reflected wave, the phase change component of said reflected wave is extracted by subtracting DC component of said signal from said reflected wave subjected to envelope detection.

13. A distance measuring program for measuring a distance to an object of measurement, causing a computer to execute the steps of:

outputting a signal having a variable frequency;

generating and emitting to said object of measurement an electromagnetic wave of the same frequency as said signal;

detecting a reflected wave of said electromagnetic wave; and

calculating a distance to said object of measurement by an operation of a relation between said detected reflected wave and the frequency of said signal;

wherein

said step of detecting a reflected wave includes the step of

extracting a phase change component of said reflected wave by synchronous detection of said detected reflected wave with said signal; and

said step of calculating the distance to said object of measurement includes the steps of

changing variable frequency of said extracted phase change component by a frequency corresponding to a prescribed distance,

taking, as an analysis signal, one of upper and lower side bands obtained by said frequency change, and

performing Fourier transform on said analysis signal to calculate a profile, and finding distance to said object of measurement based on a local maximum of said profile and said prescribed distance.

14. The distance measuring program according to claim 13, wherein

said step of outputting a signal having variable frequency includes the steps of

sweeping upward a prescribed transmission frequency with a prescribed bandwidth at a prescribed step, and

sweeping downward said prescribed transmission frequency with the prescribed bandwidth at the prescribed step;

said step of calculating the distance to said object of measurement further includes the steps of

holding, as first position information, a distance to said object of measurement obtained by said Fourier transform through said upward sweeping, and as second position information, a distance to said object of measurement obtained by said Fourier transform through said downward sweeping, and

averaging said held first position information and second position information to derive true distance to said object of measurement.

15. The distance measuring program according to claim 13, wherein

in said step of extracting phase change component of said reflected wave,

in-phase component of said phase change component is extracted by synchronous detection of said reflected wave with said signal, and quadrature component of said phase change component is extracted by synchronous detection of said reflected wave with a signal different in phase by π

/2 from said signal.

16. The distance measuring program according to claim 15, wherein

said prescribed distance is variable in accordance with a number of divisions for sweeping a prescribed transmission frequency with a prescribed bandwidth.

17. The distance measuring program according to claim 16, wherein

said prescribed distance is set, at the largest, to be approximately a half of a maximum detectable distance determined by said prescribed bandwidth and said number of divisions.

18. The distance measuring program according to claim 13, wherein

in said step of extracting the phase change component of said reflected wave, the phase change component of said reflected wave is extracted by subtracting DC component of said signal from said reflected wave subjected to envelope detection.