Distance measurement
Provided in accordance with the invention is a method for measuring the distance of an object in which a transmitted signal (S) with a pulse train having a prescribed pulse repetition frequency (fw) is generated such that the transmitted signal has a frequency comb in the frequency domain, the transmitted signal is directed onto the object, and a reflected signal (R) reflected from the object is received, the phase difference (φ MESS,1 ) between the transmitted signal and the reflected signal is determined for a prescribed spectral line of the frequency comb, and the distance is determined with the aid of the phase difference.
1. A method for measuring the distance of an object, comprising the steps of:
generating a transmitted signal (S) with a pulse train having prescribed pulse repetition frequency (fw) such that the transmitted signal has a frequency comb in the frequency domain,
directing the transmitted signal onto the object, and a reflected signal (R) reflected from the object is received,
wherein the phase difference (φ MESS,1 ) between the transmitted signal and the reflected signal is determined for a prescribed spectral line of the frequency comb, and the distance is determined with the aid of the phase difference;
wherein
the phase difference (φ MESS,2 ) between the transmitted signal and the reflected signal is determined for a second spectral line of the frequency comb, and
both the phase difference (φ MESS,1 ) between the transmitted signal and the reflected signal for the first spectral line, and the phase difference (φ MESS,2 ) between the transmitted signal and the reflected signal for the second spectral line are used in determining the distance.
2. The method as claimed in claim 1 , wherein
a test is made as to whether the phase difference (φ MESS,1 ) for the first spectral line is greater or less than the phase difference (φ MESS,2 ) for the second spectral line, and
the distance is determined as a function of the test result.
3. The method as claimed in claim 1 , wherein the second spectral line has a higher frequency than the first spectral line, and a distance value A is determined in accordance with
A
=
c
*
φ
MESS
,
2
-
φ
MESS
,
1
2
·
π
·
fw
if
it
holds
that
φ
MESS
,
1
<
φ
MESS
,
2
and
A
=
c
*
φ
MESS
,
1
-
φ
MESS
,
2
+
2
·
π
2
·
π
·
fw
if
it
holds
that
φ
MESS
,
1
>
φ
MESS
,
2
c denoting the propagation rate of the transmitted signal to the object, φ MESS,1 denoting the phase difference between transmitted signal and reflected signal for the first spectral line, φ MESS,2 denoting the phase difference between transmitted signal and reflected signal for the second spectral line and fw denoting the pulse repetition frequency.
4. The method as claimed in claim 1 , wherein two spectral lines of the frequency comb that are adjacent in the frequency spectrum are evaluated as first and second spectral lines.
5. The method as claimed in claim 1 wherein
the first and the second spectral lines of the transmitted signal and of the reflected signal are respectively downmixed to the same intermediate frequency, and
the phase difference (φ MESS,1 ) between the transmitted signal and the reflected signal for the first spectral line, and the phase difference (φ MESS,2 ) between the transmitted signal and the reflected signal for the second spectral line are determined with the aid of the downmixed signals.
6. The method as claimed in claim 5 , wherein an oscillator frequency that lies in the frequency band asymmetrically between two adjacent spectral lines of the frequency comb is used for the downmixing.
7. The method as claimed in claim 6 , wherein
the transmitted signal and the reflected signal for the first and the second spectral lines are respectively downmixed to an intermediate frequency between 1 kHz and 20 MHz, preferably to 10.7 MHz.
8. An arrangement for measuring the distance (A) of an object, comprising
a transmitter for generating a transmitted signal (S) that has a pulse train with a prescribed pulse repetition frequency (fw) in the time domain, and a frequency comb in the frequency domain,
a receiver for receiving a reflected signal (R) reflected by the object, and an evaluation device that uses the phase difference (φ MESS,1 ) between the transmitted signal and the reflected signal for a prescribed spectral line of the frequency comb in order to determine the distance;
wherein the evaluation device determines the phase difference between the transmitted signal and the reflected signal for two different spectral lines of the frequency comb, and uses the two phase differences in order to determine the distance.
9. The arrangement as claimed in claim 8 , wherein
the evaluation device is configured in such a way that it tests whether the phase difference (φ MESS,1 ) for the first spectral line is greater or less than the phase difference (φ MESS,2 ) for the second spectral line, and determines the distance as a function of the test result.
10. The arrangement as claimed in claim 8 , wherein
the arrangement has at least one switchable oscillator and at least two mixers connected to the oscillator,
the two mixers optionally downmixing the first or the second spectral line of the transmitted signal and of the reflected signal to the same intermediate frequency.
11. The arrangement as claimed in claim 10 , wherein
the oscillator frequency of the oscillator lies in the frequency band asymmetrically between two adjacent spectral lines of the frequency comb of the transmitted or reflected signal.