Distance measuring device, water level measurement system, and distance measurement method

Patent metadata

Field	Value
Publication number	US-10725165-B2
Application number	US-201815913979-A
Country	US
Kind code	B2
Filing date	Mar 7, 2018
Priority date	Mar 13, 2017
Publication date	Jul 28, 2020
Grant date	Jul 28, 2020

Abstract

A distance measuring device includes one or more processors configured to: detect a wave formed by synthesizing a frequency-swept electromagnetic wave transmitted to an object with a wave reflected on the object; measure, based on the synthesized wave, a distance to the object; calculate a displacement-caused inclination, caused by the displacement of the object, of a power spectrum of the synthesized wave; and measure the distance based on a signal in which the displacement-caused inclination has been removed from the power spectrum.

First claim

What is claimed is:

1. A distance measuring device comprising:
one or more processors configured to:
transmit a frequency swept electromagnetic wave to an object;
detect a reflected wave reflected on a surface of the object;
obtain a synthesized wave by synthesizing the frequency swept electromagnetic wave and the reflected wave for calculating, based on the synthesized wave, a distance to the object;
calculate a power spectrum inclination of the synthesized electromagnetic wave caused the displacement of the object; and
calculate the distance based on removing the displacement-caused inclination from the power spectrum.

2. The distance measuring device according to claim 1 , wherein the one or more processors is configured to calculate a regression line, corresponding to the displacement-caused inclination, of the power spectrum of the synthesized wave.

3. The distance measuring device according to claim 1 , further comprising:
an orthogonal wave detector configured to separate the synthesized wave into real-part data and imaginary-part data,
wherein the one or more processors is configured to calculate a real-part inclination corresponding to the real-part data and an imaginary-part inclination corresponding to the imaginary-part data.

4. The distance measuring device according to claim 1 ,
wherein the one or more processors are configured to calculate, based on Equation A provided below, a displacement component (V), corresponding to the displacement-caused inclination, of the power spectrum in a real-part region of the synthesized wave and calculate, based on Equation B provided below, a displacement component (V), corresponding to the displacement-caused inclination, of the power spectrum in an imaginary-part region of the synthesized wave, while

V
=

2
⁢

A
2

⁢

sin
⁡

(

4
⁢

⁢
π
⁢

⁢

fd
0

c

-
ϕ

)

·

4
⁢

⁢
π
⁢

⁢

f
0

⁢
B

c

⁢
t

,
and

Equation
⁢

⁢
A

V
=

2
⁢

A
2

⁢

cos
⁡

(

4
⁢

⁢
π
⁢

⁢

fd
0

c

-
ϕ

)

·

4
⁢

⁢
π
⁢

⁢

f
0

⁢
B

c

⁢
t

,

Equation
⁢

⁢
B

where (A) is an amplitude level of the transmitted wave, (f) is the frequency of the transmitted wave, (d 0 ) is a central value of the distance, (c) is the speed of light, (ϕ) is the amount of a change in the phase due to the reflection, (f 0 ) is a central frequency of the transmitted wave, (B) is a velocity coefficient that gives the displacement Δd of the obje

Assignees

• Fujitsu Ltd

Inventors

• Kikuchi Yoshio
• Tsuboi Osamu

Classifications

• G01F23/284 Primary

  Electromagnetic waves · CPC title

• G01F23/804

  containing circuits handling parameters other than liquid level · CPC title

• G01S13/34 Primary

  using transmission of continuous, frequency-modulated waves while heterodyning the received signal, or a signal derived therefrom, with a locally-generated signal related to the contemporaneously transmitted signal · CPC title

• G01S7/4026

  Antenna boresight · CPC title

• G01S13/88

  Radar or analogous systems specially adapted for specific applications (electromagnetic prospecting or detecting of objects, e.g. near-field detection, G01V3/00) · CPC title