Method for measuring a distance running time
A method for ascertaining the distance on the basis of the travel-time of high-frequency measuring signals, wherein at least one periodic, pulsed, transmission signal having a pulse repetition frequency is transmitted and at least one reflected measuring signal is received. The transmission signal and the reflected measuring signal are transformed by means of a sampling signal produced with a sampling frequency into a time-expanded, intermediate-frequency signal having an intermediate-frequency. The time-expanded, intermediate-frequency signal is filtered by means of at least one filter and a filtered, intermediate-frequency signal is produced, wherein the intermediate-frequency is matched to a limit frequency and/or a center frequency of the filter. The matching of the filter to the intermediate-frequency of the time-expanded measuring signal results, reducing production costs.
1 - 10 . (canceled)
11 . A method for ascertaining the distance on the basis of travel-time of high-frequency measuring signals, comprising the steps of:
transmitting at least one periodic, pulsed transmission-signal of pulse repetition frequency;
receiving at least one reflected measuring signal;
transforming the transmission signal and the reflected measuring signal by means of a sampling signal having a sampling frequency into a time-expanded, intermediate-frequency signal having an intermediate-frequency;
filtering the time-expanded, intermediate-frequency signal by means of at least one filter and producing a filtered intermediate-frequency signal; and
matching the intermediate-frequency to a limit frequency and/or a center frequency of the filter.
12 . The travel-time measuring method as claimed in claim 11 , wherein:
the intermediate-frequency is matched by so varying the pulse repetition frequency and/or the sampling frequency, that the frequency difference between the pulse repetition frequency and the sampling frequency is changed.
13 . The travel-time measuring method as claimed in claim 12 , wherein:
the intermediate-frequency is matched by varying the pulse repetition frequency and/or the sampling frequency according to an iterative method.
14 . The travel-time measuring method as claimed in claim 11 , wherein:
the matching of the intermediate-frequency is checked by evaluating the signal strength of the filtered intermediate-frequency signal.
15 . The travel-time measuring method as claimed in claim 11 , further comprising the step of:
periodically introducing a control process or under event-control for the matching of the intermediate-frequency.
16 . The travel-time measuring method as claimed in claim 14 , wherein:
the signal strength of the filtered intermediate-frequency signal is determined by an algorithm from the filtered intermediate-frequency signal, by ascertaining amplitude of a fill level echo and/or by ascertaining an integral over all data points of the filtered intermediate-frequency signal.
17 . The travel-time measuring method as claimed in claim 12 , wherein:
a transformation factor, which corresponds to a time-expansion ratio, is ascertained from a pulse repetition frequency to frequency difference ratio.
18 . The travel-time measuring method as claimed in claim 17 , wherein:
the transformation factor is transmitted for further evaluation and processing of the filtered, time-expanded, intermediate-frequency signal.
19 . The travel-time measuring method as claimed in claim 11 , wherein:
mirror frequencies of the intermediate-frequency and/or the sampling sum signal are masked out of the time-expanded, intermediate-frequency signal by a lowpass.
20 . The travel-time measuring method as claimed in claim 11 , wherein:
disturbance signals, especially noise, are masked out of the time-expanded, intermediate-frequency signal by a bandpass.