Device for distance measurement and method for functionally checking a device for distance measurement

A method for functionally checking a device for distance measurement, the device including at least one signal generator for generating an electromagnetic measurement signal, at least one transmitting antenna for transmitting the measurement signal, at least one receiving antenna for receiving a received signal, wherein the signal generator is connected at least to the transmitting antenna, at least a first mixer, wherein a first input of the first mixer is connected to the signal generator and wherein a second input of the first mixer is connected at least to the receiving antenna, so that, during operation, the first mixer mixes at least the measurement signal generated by the signal generator and the received signal received by the receiving antenna, an evaluation unit;

• and an integrated diagnostic unit having at least one diagnostic line, wherein the signal generator is connected to the diagnostic line in such a way that, during operation, the measurement signal generated by the signal generator is at least partially coupled into the diagnostic line, wherein the diagnostic line has at least one delay element, wherein the measurement signal is formed as a diagnostic signal after at least one pass through the delay element during operation, wherein the diagnostic line is connected to the first mixer or to a second mixer, so that, during operation, the diagnostic signal is mixed with the measurement signal in the first mixer or in the second mixer to form a diagnostic mixed signal, and wherein the output of the first mixer, and if present the output of the second mixer, is or are connected to the evaluation unit, and that the evaluation unit is designed to use the diagnostic mixed signal to check the functionality of the signal generator and/or of the evaluation algorithm, the method comprising:
• emitting an electromagnetic measurement signal by the signal generator, wherein a part of the measurement signal is fed into the first mixer and wherein a part of the measurement signal couples into the diagnostic line so that the measurement signal passes through the delay element at least once and thus becomes the diagnostic signal, and feeding the measurement signal into a second mixer;
• mixing the diagnostic signal with the measurement signal in the first mixer or in the second mixer and generating a diagnostic mixed signal;
• detecting and evaluating the diagnostic mixed signal by the evaluation unit;
• and
• wherein the evaluation unit determines the frequency of the diagnostic mixed signal for evaluation and compares the frequency with a reference value and/or wherein the distance corresponding to the delay element is determined from the diagnostic mixed signal and compared with a reference value.