Patent ID: 9645003
Date: 2017-05-09
CPC Classifications: G01F,G01S

Claim:
1. A method for determining distance to a surface of a medium or to another radar target in a pipe by means of a radar measurement apparatus, which works according to the principle of FMCW radar, wherein the method comprises: a) transmitting within the pipe a radar transmission signal frequency modulated according to the FMCW principle; b) receiving a radar received signal reflected on the surface of the medium or on the other radar target in the pipe back to the radar measurement apparatus; c) mixing the radar received signal with the radar transmission signal or a signal derived therefrom and producing an intermediate signal; d) determining a frequency spectrum of the intermediate signal or a signal derived therefrom by means of fast Fourier transformation and detecting the position of the frequency peak in the frequency spectrum; e) determining a dispersion correction for removing, respectively lessening, dispersion effects, applying the dispersion correction to the intermediate frequency signal or to a signal derived therefrom and producing a dispersion corrected signal; and f) determining the position of the frequency peak in the frequency spectrum of the dispersion corrected signal anew by: f1) introducing a number of frequency support points in the region of the frequency peak detected in step d); f2) determining the respective frequency amplitudes selectively at the newly introduced frequency support points by means of discrete Fourier transformation or by means of the Goertzel algorithm; and f3) ascertaining the position of the frequency peak in the frequency spectrum of the dispersion corrected signal using the frequency amplitudes at the newly introduced frequency support points and deriving the distance to the surface of the medium or to the other radar target in the pipe from the position of the frequency peak in the frequency spectrum.