Method for measuring distance by appropriate fourier transform and radar system for implementing the method

Patent metadata

Field	Value
Publication number	US-11604270-B2
Application number	US-201916712864-A
Country	US
Kind code	B2
Filing date	Dec 12, 2019
Priority date	Dec 20, 2018
Publication date	Mar 14, 2023
Grant date	Mar 14, 2023

Abstract

A radar system configured to determine radar-ground distance measurements. The radar system includes transmission and reception means configured to transmit two radiofrequency signals towards the ground and to receive the signals obtained by the reflection of the two transmitted signals by the ground and computation means configured to determine the frequential representations of the transmitted signals and of the received signals and determine a frequential quantity as a function of the frequential representations. The radar system is wherein the computation means are configured to sample the frequential quantity over a determined number of samples, which provides a sampled signal; determine a number of frequency measurements as a function of a constant distance measurement accuracy value; determine frequency measurements by applying to the sampled signal a spectral decomposition by fast Fourier transform using a decimation of the sampled signal in a ratio dependent on the distance measurement accuracy value, and determine a distance measurement corresponding to each frequency measurement.

First claim

The invention claimed is:

1. A radar system configured to determine radar-ground distance measurements, the radar system comprising:
transmission and reception means configured to transmit two radiofrequency signals towards the ground and to receive the signals obtained by the reflection of the two transmitted signals by the ground;
computation means configured to:
determine the frequential representations of the transmitted signals and of the received signals;
determine a frequential quantity as a function of said frequential representations;
the radar system being wherein the computation means are configured to:
sample said frequential quantity over a determined number of samples, which provides a sampled signal;
determine a number of frequency measurements as a function of a constant distance measurement accuracy value;
determine frequency measurements by applying to the sampled signal a spectral decomposition by fast Fourier transform over said number of measurements, the Fourier transform using a decimation of the sampled signal in a ratio dependent on said distance measurement accuracy value, and
determine a distance measurement corresponding to each frequency measurement.

2. The radar system according to claim 1 , wherein the transmitted signals are composed of a first transmitted radiofrequency signal and of a second transmitted radiofrequency signal, the received signals being composed of a first received signal and of a second received signal, the first received signal corresponding to the signal obtained by the reflection of said first transmitted signal by the ground, the second received signal corresponding to the signal obtained by the reflection of said second transmitted signal by the ground, the computation means being configured to determine said frequential quantity by calculating the difference between a first frequential signal and a second frequential signal, said first frequential signal corresponding to the difference between the frequential representation of the first received signal and the frequential representation of the first transmitted signal, the second frequential signal corresponding to the difference between the frequential representation of the second received signal and the frequential representation of the second transmitted signal.

3. The radar system according to claim 1 , wherein the computation means are configured to sample said frequential quantity according to a sampling period, the computation means being configured to determine a minimum sampling period as a function of a maximum frequency value and to determine a number of samples of the sampled signal as a function of a minimum frequency value and of said minimum sampling period.

4. The radar system according to claim 1 , wherein the computation means are configured to determine an intermediate parameter as a function of said distance measurement accuracy value, said intermediate parameter being calculated by dividing a first value by a second value, said first value being calculated by adding said measurement accuracy value to the value two, said second value being calculated by subtracting said distance measurement accuracy value from the value two, the computation means being configured to determine said number of frequency measurements as a function of a minimum frequency value, of a maximum frequency value and of said intermediate parameter.

5. The radar system according to claim 4 , wherein the computation means are configured to determine the number of frequency measurements by the division of a first logarithmic function by a second logarithmic function, the first logarithmic function corresponding to the Napierian logarithm of the ratio between the maximum frequency value and the minimum frequency value, the second logarithmic function corresponding to the Napierian logarithm of said intermediate parameter.

6. A method for determining radar-ground distance measurements comprising:
the transmission of two radiofrequency signals towards the ground and the reception of the signals obtained by the reflection of the two transmitted signals by the ground;
the determination of frequential representations of the transmitted signals and of the received signals;
the determination of a frequential quantity as a function of said frequential representations;
the method being wherein it comprises the steps comprising:
the sampling of said frequential quantity over a determined number of samples, which provides a sampled signal;
the determination of a number of frequency measurements as a function of a constant distance measurement accuracy value;
the determination of frequency measurements by applying to the sampled signal a spectral decomposition by fast Fourier transform over said number of measurements, the Fourier transform using a decimation of the sampled signal in a ratio dependent on said distance measurement accuracy value, and
the determination of a distance measurement corresponding to each frequency measurement.

Assignees

• Thales Sa

Inventors

• Mazeau Thierry
• Garrec Patrick

Classifications

• G01S13/08

  Systems for measuring distance only (indirect measurement G01S13/46) · CPC title

• G06F17/142

  Fast Fourier transforms, e.g. using a Cooley-Tukey type algorithm · CPC title

• G06F7/556

  Logarithmic or exponential functions · CPC title

• G01S13/345 Primary

  using triangular modulation · CPC title

• G01S7/356

  involving particularities of FFT processing · CPC title