TEST DEVICE FOR TESTING A DISTANCE SENSOR THAT OPERATES USING ELECTROMAGNETIC WAVES, AND FREQUENCY DIVIDER ASSEMBLY FOR SUCH A TEST DEVICE

Abstract

A test device for testing a distance sensor that operates using electromagnetic waves, said test device comprising: a receiving element for receiving an electromagnetic free-space wave as a received signal with a reception frequency and a signal bandwidth. An emission element emits an electromagnetic output signal. During a simulation operation, the received signal or a received signal derived from the received signal is converted into a sampled signal by an analog-to-digital converter. The sampled signal is time-delayed using a signal processing unit to form a time-delayed sampled signal. The time-delayed sampled signal is converted into a simulated reflection signal by a digital-to-analog converter. The simulated reflection signal or a simulated reflection signal derived from the simulated reflection signal is emitted as an output signal by the emission element.

Claims

1. A test device to test a distance sensor that operates using electromagnetic waves, the test device comprising: a receiver to receive an electromagnetic free-space wave as a received signal with a reception frequency and a signal bandwidth; an emitter to emit an electromagnetic output signal, wherein, during a simulation operation, the received signal or a received signal derived from the received signal is converted into a sampled signal via an analog-to-digital converter, the sampled signal being time-delayed using a signal processing unit; a digital-to-analog converter to convert the time-delayed sampled signal into a simulated reflection signal, the simulated reflection signal or a reflection signal being derived from the simulated reflection signal is emitted as an output signal by the emitter; a signal splitter to divide the received signal into a first partial received signal and a second partial received signal, at least the second partial received signal containing amplitude information of the received signal; a frequency divider to convert the first partial received signal into a frequency-divided received signal that no longer contains the amplitude information of the received signal; an amplitude detector to obtain amplitude information of the received signal from the second partial received signal; a modulator to generate a frequency-divided received signal with the amplitude information of the received signal by modulating the amplitude information obtained from the second partial received signal onto the frequency-divided received signal without amplitude information and thus generating the received signal derived from the received signal; and a frequency multiplier to convert the simulated reflection signal to the signal derived from the simulated reflection signal.

2. The test device according to claim 1, wherein the signal splitter is a resistive power divider.

3. The test device according to claim 1, wherein the frequency divider is based on digital technology or bistable flip-flops.

4. The test device according to claim 1, wherein the amplitude detector is a rectifier and a downstream low-pass, or a diode as rectifier.

5. The test device according to claim 1, wherein a division factor of the frequency divider is chosen such that the lowest frequency of the frequency-divided received signal is equal to or greater than the signal bandwidth multiplied by half the division factor.

6. The test device according to claim 1, wherein a low-pass filter filters the frequency-divided received signal with the amplitude information so that the harmonic fundamental oscillation of the frequency-divided received signal as a derived received signal.

7. The test device according to claim 6, wherein the cut-off frequency of the low-pass is between two and three times a lowest frequency of the frequency-divided received signal.

8. The test device according to claim 1, wherein a multiplication factor of the frequency multiplier corresponds to a reciprocal of the division factor of the frequency divider.

9. The test device according to claim 1, wherein the frequency multiplier is a semiconductor component with nonlinear transmission behavior for the generation of harmonics, or is a diode or is a transistor.

10. The test device according to claim 1, wherein the received signal is shifted to lower frequencies with a receiving converter, and wherein the output signal of the frequency multiplier is shifted to higher frequencies with an output converter where frequency shifts are equal in magnitude.

11. A frequency divider array for the test device according to claim 1, wherein a received signal is divided into a first partial received signal and a second partial received signal using a signal splitter, wherein at least the second partial received signal contains the amplitude information of the received signal, wherein the first partial received signal is converted by a frequency divider into a frequency-divided received signal no longer containing the amplitude information of the received signal, wherein the amplitude information is obtained from the second partial received signal using an amplitude detector of the received signal, wherein a modulator is used to generate a frequency-divided received signal with the amplitude information of the received signal by modulating the amplitude information obtained from the second partial received signal onto the frequency-divided received signal without amplitude information and thus generating a derived received signal from the received signal.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

[0034] FIG. 1 shows a schematic test device for testing a distance sensor that operates using electromagnetic waves, as known from the prior art,

[0035] FIG. 2 shows a schematic amplitude spectra of the received signal and the received signal derived from the received signal, also as known from the prior art,

[0036] FIG. 3 shows a frequency divider array as it is realized in the reception path of the test device according to the invention,

[0037] FIG. 4 shows a schematic frequency multiplier in the output path of the test device according to an example of the invention,

[0038] FIG. 5 shows a schematic of an example of a frequency divider array of the test device,

[0039] FIG. 6 shows a schematic of an example of a frequency divider array in the test device,

[0040] FIG. 7 shows schematic of a test device with input and output frequency converter, and

[0041] FIG. 8 shows schematic amplitude spectra of different signals when using the frequency divider array in the test device.

DETAILED DESCRIPTION

[0042] FIG. 1 shows a test device 1 known from the state of the art for testing a distance sensor 2 that operates using electromagnetic waves. The distance sensor 2, for example, is a radar distance sensor as used in the automotive sector. The distance sensor 2 emits a free-space wave that is reflected off a reflection object and receives the reflection signal. From the time delay, a frequency shift and, if applicable, the signal intensity of the reflection signal, the distance sensor can infer the distance from the reflection object, radial velocity components of the reflection object and, if applicable, the size, reflection properties, etc. of the reflection object; this depends on the design of the distance sensor 2. The test device 1 simulates an actual reflection object to the distance sensor 2 to be tested.

[0043] The test device 1 has a receiving element 3 for receiving the electric free-space wave emitted by a distance sensor 2 as a received signal S.sub.RX. The S.sub.RX received signal has a reception frequency f.sub.RX and a signal bandwidth B. Furthermore, the test device 1 has an emission element 4 for the emission of an electromagnetic output signal S.sub.TX.

[0044] In a simulation operation, the received signal S.sub.RX or a received signal S.sub.RX derived from the received signal S.sub.RX is converted into a sampled signal by means of an analog-to-digital converter 5, the sampled signal is converted into a time-delayed sampled signal with a signal processing unit 6, and the time-delayed sampled signal is converted into a simulated reflection signal S.sub.sim by means of a digital-to-analog converter 7. The simulated reflection signal S.sub.sim or a simulated reflection signal S.sub.sim derived from the simulated reflection signal S.sub.sim is then emitted as an output signal S.sub.TX via the emission element 4.

[0045] With the signal processing unit 6, the necessary measures are implemented to provide the simulated reflection signal with all essential signal properties, i.e., a desired signal delay, a desired frequency shift (or even several, differently frequency-shifted signal components) and, if necessary, also the desired amplitude of the simulated reflection signal S.sub.sim.

[0046] In addition, as indicated in FIG. 1, there may be signal processing 8a upstream on the input side and also signal processing 8b downstream on the output side to the signal processing of the signal processing unit 6. For example, it is known to use an input mixer to downmix the received signal S.sub.RX to a lower frequency range while preserving the bandwidth of the signal.

[0047] This results in the received signal S.sub.RX derived from the received signal S.sub.RX. This situation is shown in FIG. 2 by an amplitude spectrum. The received signal S.sub.RX has a bandwidth B of 4 GHz with a reception frequency f.sub.RX of 79 GHz. The signal bandwidth B therefore extends from 77 GHz to 81 GHz. By using a mixer, which is part of the signal processing 8a upstream on the input side, the received signal S.sub.RS is downmixed to an intermediate frequency of 4 GHz using a frequency of 75 GHz of a local oscillator, whereas the signal bandwidth B is retained. In this example, the received signal S.sub.RX derived from the received signal S.sub.RX is created.

[0048] It is not explicitly shown that the signal processing 8b downstream on the output side uses a corresponding mixer with which the low-frequency simulated reflection signal S.sub.sim is mixed up again into the range of the reception frequency f.sub.RX and then emitted as a derived simulated reflection signal S.sub.sim. Since the bandwidth B of the received signal S.sub.RX remains unchanged, the requirements dependent on the signal bandwidth B with regard to the sampling of the signal remain the same and remain high.

[0049] FIGS. 3 to 8 describe various aspects of a test device 1 according to the invention for testing the distance sensor 2 that operates using electromagnetic waves as well as a frequency divider array 9 according to the invention, which is part of the test device 1.

[0050] In FIG. 3, a frequency divider array 9 is first shown, which is part of the signal processing upstream on the input side. It can be seen that the received signal S.sub.RX is divided into a first partial received signal S.sub.1 and a second partial received signal S.sub.2 with a signal splitter 10, wherein at least the second partial received signal S.sub.2 has the amplitude information A of the received signal S.sub.RX. In the present case, the signal splitter 10 is a resistive power divider, so that the first partial received signal S.sub.1 also basically has the amplitude information A of the received signal S.sub.RX. The first partial received signal S.sub.1 is converted with a frequency divider 11 into a frequency-divided received signal S.sub.1f that no longer has the amplitude information A of the received signal S.sub.RX. The frequency-divided received signal S.sub.1f does not have the amplitude information A because the frequency divider 11 outputs a digital output signal that still has the frequency information but no longer contains the amplitude information of the frequency-divided input signal.

[0051] From the second partial received signal S.sub.2, the amplitude information A of the received signal S.sub.RX is obtained with an amplitude detector 12. In the present case, the envelope of the second partial received signal S.sub.2 is detected.

[0052] Finally, a frequency-divided received signal S.sub.fA with the amplitude information A of the received signal S.sub.RX is generated with a modulator 13 by modulating the amplitude information A obtained from the second partial received signal S.sub.2 onto the frequency-divided received signal without amplitude information S.sub.1f. In this way, the received signal S.sub.RX derived from the received signal S.sub.RX is generated. With the described frequency divider array 9, it is possible to compensate for the loss of the amplitude information A when using a frequency divider 11 in a clever way by recovering the amplitude information A in a separate signal path and modulating the frequency-divided received signal S.sub.1f that no longer has the amplitude information A again.

[0053] The use of the frequency divider 11 has the advantage that the reception frequency f.sub.RX, i.e., the center frequency of the received signal S.sub.RX, is not only reduced by the division factor 1/x of the frequency divider 11, but also that the signal bandwidth B of the received signal S.sub.RX is reduced by the same factor, so that the requirements for further signal processing are correspondingly lower.

[0054] FIG. 4 shows a further aspect of the test device 1, namely that the simulated reflection signal S.sub.sim is converted to the signal S.sub.sim derived from the simulated reflection signal S.sub.sim with a frequency multiplier 14. In the present case, the multiplication factor y of the frequency multiplier 14 is equal to the reciprocal of the division factor 1/x of the frequency divider 11.

[0055] This accurately cancels out the effects of the frequency divider 11 (lowering the center frequency and reducing bandwidth).

[0056] In the examples shown, the frequency divider 11 is implemented using digital technology, namely on the basis of fast bistable flip-flops.

[0057] In the examples shown, the amplitude detector 12 is realized with a rectifier and a downstream low-pass, namely with a diode as a rectifier.

[0058] FIG. 5 shows that the frequency divider 11 is followed by a low-pass filter 18, which only allows the harmonic fundamental oscillation of the frequency-divided received signal to pass through without amplitude information S.sub.1f. In this way, the square-wave signal resulting from the frequency division can be easily converted into a clean sinusoidal oscillation.

[0059] FIG. 6 shows an alternative implementation of the test device 1 or the frequency divider array 9, in which the low-pass filter 18 filters the frequency-divided received signal with the amplitude information S.sub.fA in such a way that only the harmonic fundamental oscillation of the frequency-divided received signal S.sub.fA results as a derived received signal S.sub.RX.

[0060] In both of the above-mentioned examples according to FIGS. 5 and 6, the low-pass 18 is designed in such a way that its cut-off frequency is between twice and three times the lowest frequency of the frequency-divided received signal S.sub.1f, S.sub.fA.

[0061] The examples also have in common that the multiplication factor y of the frequency multiplier 14 corresponds to the reciprocal of the division factor x of the frequency divider 11, which cancels out the frequency shifts as well as the bandwidth reduction and bandwidth expansion on the input and output sides.

[0062] The test devices 1 in the examples have in common that the frequency multiplier 14 is realized using a diode for the generation of harmonics. To filter a harmonic, in this case the one with four times the fundamental frequency, a bandpass is downstream.

[0063] FIG. 7 shows a test device 1 in which the received signal S.sub.RX is shifted towards low frequencies with a receiver converter 15 and in which the output signal of the frequency multiplier 14 is shifted to higher frequencies with an output converter 16, wherein the frequency shifts here are equal in magnitude. The receiving converter 15 and the output converter 16 are mixers to which a local oscillator 17 applies a harmonic signal with a corresponding frequency for increasing and decreasing the respective frequency of the input signal. The received signal S.sub.RX is already frequency-shifted here before it is further processed by the frequency divider array 9 in the manner described. In order not to have to use other identifiers, it is referred to as the received signal S.sub.RX.

[0064] FIG. 8 shows the amplitude spectrum of various signals that result from the use of the frequency divider array 9 in the test device 1 according to FIG. 7. Here, too, the received signal S.sub.RX has a bandwidth B of 4 GHz with a center frequency of 79 GHz. The receiver converter 15 is fed by the local oscillator 17 with a mixing frequency of 75 GHz, so that the reduced received signal S.sub.RX with the unchanged bandwidth B of 4 GHz results in the range of 2 to 6 GHz. This signal is used to feed the frequency divider array 9, wherein the frequency divider 11 used has a division factor 1/x=. The bandwidth B is therefore reduced by a factor of 4, i.e., to 1 GHz. The limiting frequencies are also reduced by a factor of 4 and are now 0.5 GHz and 1.5 GHz. When choosing the division factor 1/x, care was taken to ensure that the lowest frequency of the frequency-divided received signal S.sub.1f is equal to or greater than the signal bandwidth B of the received signal multiplied by half the division factor 1/x, i.e., multiplied by 1/(2x).

[0065] The bandwidth-reduced (B/x) received signal S.sub.RX, derived from the received signal S.sub.RX, is easier to handle by the following digital signal processing than a signal with the original, larger bandwidth B. Therefore, it is possible to use less fast power electronic components, which enables the use of less sophisticated and thus often cheaper hardware components.

[0066] 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.