Radar fill level measurement device
A radar based fill level measurement device for measuring the fill level of a material in a container, comprising an electronics unit, wherein the electronics unit serves to generate a transmission signal, and serves to process a received signal. The received signal containing a reflected portion of the transmission signal, and the reflected portion being reflected from a surface of the material whose distance is to be measured. The electronics unit comprises a signal generator to generate a frequency modulated transmission signal, wherein the electronics unit comprises a processor to process the received signal using phase information comprised in the received signal, and wherein the radar device comprises a coaxial waveguide probe arranged in the container, wherein said coaxial waveguide probe serves for guiding the transmission signal (TX) and the received signal (RX).
1. A radar based fill level measurement device for measuring the fill level of a material in a container, comprising:
an electronics unit, which serves to generate a transmission signal, and serves to process a received signal, said received signal containing a reflected portion of the transmission signal, said reflected portion being reflected from a surface of the material whose distance is to be measured; and
a coaxial waveguide probe, wherein:
said electronics unit comprises a signal generator to generate a frequency modulated transmission signal,
said electronics unit comprises a processor to process the received signal using phase information comprised in the received signal;
said processor calculates an expected phase response of the received signal (RX) as a function of the distance of the surface of the material;
said processor determines the phase of the received signal (RX) at a frequency peak (X) of the received signal; wherein said frequency peak (X) corresponds to said distance, and
said processor compares said determined phase with the expected phase response at said distance; and
said coaxial waveguide probe serves for guiding the transmission signal and the received signal.
2. The radar based fill level measurement device according to claim 1 , wherein:
a wave impedence of said coaxial waveguide probe corresponds to an output impedence of said electronics unit.
3. The radar based fill level measurement device according to claim 2 , wherein:
said wave impedence is adjusted through an adjustment of the inner diameter of an outer conductor of said coaxial waveguide probe.
4. The radar based fill level measurement device according to claim 1 , wherein:
said processor determines the placement of the frequency peak (X) in a frequency spectrum of an intermediate frequency signal (IF) by interspersing additional frequency points in between and/or adjacent to sampled frequencies obtained by a fast fourier transform of the intermediate frequency signal (IF) sampled by an analog to digital converter of said electronics unit; and
said sampled frequencies comprise respective spectral amplitudes that are greater than a predetermined amplitude threshold.
5. Radar based fill level measurement device according to claim 4 , wherein:
said processor performs a discrete fourier transform at the sampled frequencies and additional frequency points.
6. Radar based fill level measurement device according to claim 4 , wherein:
said processor applies a generalized goertzel algorithm at the sampled frequencies and additional frequency points.
7. Radar based fill level measurement device according to claim 1 , wherein:
said processor determines the phase of the frequency peak (X) by applying a generalized goertzel algorithm at an additional frequency point or a sampled frequency in the frequency peak (X); and
said frequency point or said sampled frequency comprises a greater spectral amplitude than any adjacent frequency point or sampled frequency.