Patent ID: 12259493

DETAILED DESCRIPTION

FIG.1shows a schematic view of a radar target simulator1for generating a simulated radar echo signal with a receiving antenna2for receiving a radar signal in the target simulator1, a low-pass filter3, a computing unit4, and a transmitting antenna5. A radar sensor to be tested6is arranged relative to the radar target simulator1in such a way that radar signals emanating from the radar sensor6can be received by the receiving antenna2of the radar target simulator1. As can be seen fromFIG.1, the transmitting antenna5and the receiving antenna2of the radar target simulator1are designed as individual devices which are separate from each other. Whereas the receiving antenna2of the radar target simulator1is fixed, the transmitting antenna5, as indicated by two arrows, is movable, in a circle approximately 180° around the radar sensor to be tested6. This allows for the simulation of radar signals reflected by fictitious objects that are not only located exactly in front of the radar sensor to be tested6, but also to the side of it.

The low-pass filter3is an anti-aliasing filter with a known filter curve, which, however, has such a cut-off frequency that does not allow the radar signal emitted by the radar sensor to be tested6to be sampled over its entire bandwidth. In the case of the previously described radar target simulator1in a conventional operation, this would in principle lead to the generation of a faulty simulated radar echo signal for the reasons already mentioned above. Therefore, according to an exemplary embodiment of the invention, the following method is for generating a simulated radar echo signal, which has the following method steps and is schematically illustrated inFIG.2:

In a first step S1, a radar signal with known bandwidth is sent from the radar sensor to be tested6to the receiving antenna2of the radar target simulator1. There, the radar signal is received in step S2with the receiving antenna2. In the following step S3, the radar signal is filtered in the radar target simulator1in a known manner by means of the low-pass filter3there in order to avoid or reduce aliasing effects. Up to this point, the presently described method substantially corresponds to the conventional methods for operating a radar target simulator.

In step S4, however, the frequency spectrum of the filtered model signal is determined over the entire bandwidth of the low-pass filter given by the filter curve. A calculation of a corrected frequency spectrum by correcting the previously determined frequency spectrum by means of the filter curve in such a way that, as a corrected frequency spectrum, such a frequency spectrum is obtained which corresponds to the frequency spectrum of the emitted unfiltered radar signal is carried out below in step S5. Then, in step S6, the power of a radar signal corresponding to the corrected frequency spectrum is calculated. Thereafter, in step S7, a scaled radar signal is calculated from the filtered radar signal, wherein the power of the scaled radar signal is equal to the power of the radar signal corresponding to the corrected frequency spectrum in that the amplitude of the filtered radar signal over its entire frequency spectrum is subjected to scalar multiplication equal for all frequencies. On the basis of this scaled radar signal, a radar echo signal is finally calculated in step S8, and the radar echo signal is emitted from the transmitting antenna5of the radar target simulator1to the radar sensor to be tested6. The radar echo signal is calculated as a reflection of the scaled radar signal. The emitted radar echo is therefore an artificially simulated radar echo of the scaled radar signal, not the radar signal received by the receiving antenna2.

The calculation of the corrected frequency spectrum by correcting the previously determined frequency spectrum by means of the filter curve, in such a way that a frequency spectrum is obtained which corresponds to the frequency spectrum of the emitted unfiltered radar signal, is carried out by taking into account the attenuation of the filter known from the filter curve: Since it is known from the filter curve for each frequency how large the attenuation is due to the filter, in this way the unattenuated amplitude of each frequency fraction of the emitted radar signal can be inferred from the attenuated amplitude. In this way, the signal can be manipulated in such a way that, as in the present case, the use of target simulators with a lower bandwidth than the radar sensor also leads to a correct determination of the radar cross section in the radar. Thus, with an otherwise conventional radar target simulator1, which has been upgraded by the previously described method, radar sensors with higher bandwidth can also be tested with regard to determining the radar cross section. The only prerequisite for this is that the filter curve of the target simulator is known and that the transition range of the filter covers a sufficiently large frequency spectrum. Thus, based on the known radar sensor bandwidth, it can be determined how large the lost power share is, so that correspondingly more power can be transmitted from the target simulator1by means of the transmitting antenna5to compensate for the lost power share. Overall, the radar cross section in the radar sensor indirectly determined in this way leads to the desired (correct) result, although the signal in the radar target simulator1has been limited in bandwidth.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.