JP3898626B2 - Signal processor with fault diagnosis function - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a processing device with a failure diagnosis function capable of performing operation control signal processing in a motion control device such as a vehicle and signal processing for failure diagnosis processing of the operation control device.
[0002]
[Prior art]
The failure diagnosis device for analog circuits in the prior art adds a signal generator for failure diagnosis to the circuit to be diagnosed via an electronic switch or the like, and controls the electronic switch or the like only at the time of diagnosis. The method of diagnosing a failure by disconnecting the connection between the circuit and the circuit to be diagnosed and connecting the signal generator for failure diagnosis to the circuit to be diagnosed has become the mainstream.
[0003]
This is because when a diagnostic signal and a normal processing signal are superimposed on a circuit to be diagnosed, the diagnostic signal is processed as a normal processing signal and the processed signal is output. It is because there is a possibility of damaging.
[0004]
Note that a failure diagnosis apparatus using the above-described method is described in Patent Document 1 and Patent Document 2.
[0005]
[Patent Document 1]
JP 2002-82714 A [Patent Document 2]
Japanese Examined Patent Publication No. 6-9426 [0006]
[Problems to be solved by the invention]
However, in the above prior art, as described above, since it is a method of switching between connecting a normal signal generation unit or a failure diagnosis signal generation unit to a circuit to be diagnosed, as an additional means, A switching element such as an electronic switch and software for controlling the switching timing are required.
[0007]
When switching operations such as those described above are involved, the reliability of the operation of the electronic switch, etc. and the reliability of the software affect the reliability of the entire signal processing device with the fault diagnosis function. Therefore, a high degree of reliability is required, which causes an increase in cost.
[0008]
Furthermore, since normal processing functions are temporarily suspended during diagnosis, adjustment of the timing of diagnosis is necessary to maintain the reliability of normal processing functions such as operation control. The processing function could not be executed and diagnosed.
[0009]
In view of the above problems, the object of the present invention is that there is no need to switch the connection between a normal signal generation unit and a failure diagnosis signal generation unit for a circuit to be diagnosed, and a diagnosis is performed while executing a normal processing function. It is to realize a signal processing apparatus with a fault diagnosis function capable of performing the above.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is configured as follows.
(1) In a signal processing apparatus with a fault diagnosis function, a signal processing unit to which a signal to be processed having a first frequency obtained from an object is supplied, and the signal processing unit superimposed on the first signal to be processed A fault diagnosis signal generator for outputting a fault diagnosis signal of the second frequency supplied to the signal, and a signal processed by the signal processing unit, and the supplied signal is supplied to the first frequency of the first frequency A frequency classification unit that classifies a signal, a signal of the second frequency, a failure diagnosis unit that diagnoses a failure of the signal processing unit based on the signal of the second frequency that is classified by the frequency classification unit; An information processing unit that extracts and processes information about the object based on the signal of the first frequency sorted by the frequency sorting unit.
[0011]
(2) A sensor that outputs an analog signal corresponding to a change in the surrounding environment, an analog circuit that performs signal processing on the output signal from the sensor, an A / D converter that digitally converts the output signal of the analog circuit, In a signal processing apparatus with a fault diagnosis function having a digital circuit for processing a sensor signal converted into a digital value by an A / D converter, a diagnostic signal for diagnosing a fault of the analog circuit is generated, A diagnostic signal generation circuit that superimposes the diagnostic signal and the sensor signal and inputs the signal to the analog circuit, and a digital conversion of the output signal from the analog circuit, and a signal processing to separate the sensor signal and the diagnostic signal And a failure judgment for judging failure of the analog circuit and the A / D converter using the diagnostic signal sorted by the sorting means. And means.
[0012]
(3) Preferably, in (2) above, when it is determined that the sensor signal and the diagnostic signal are within a certain classification range of the classification means and cannot be classified, generation of the diagnostic signal and fault diagnosis Is prohibited.
[0013]
(4) Preferably, in the above (2) and (3), the failure determination means determines a failure by comparing with a value of a diagnostic signal when the analog circuit and the A / D converter are normal. I do.
[0014]
(5) Preferably, in the above (2), (3), and (4), the separation means separates the sensor signal and the diagnostic signal by FFT processing.
[0015]
(6) Preferably, in the above (2), (3), (4), (5), the sensor transmits a radio wave to the front or rear side of the vehicle and detects a reflected wave from the object. Then, an analog signal corresponding to the detected signal is output.
[0016]
(7) A signal processing unit to which a signal to be processed within a first frequency range obtained from an object is supplied, and a signal processing unit that is superimposed on the signal to be processed and supplied to the signal processing unit and within the first frequency range A signal processing device with a failure diagnosis function, comprising: a failure diagnosis signal generation unit that outputs a failure diagnosis signal of the second frequency; and a computer that performs information processing based on an output signal from the signal processing unit. In the computer operation program, frequency analysis is performed on the output signal from the signal processing unit to determine whether the signal to be processed has a frequency equivalent to the second frequency, and the signal to be processed is the first signal. When having a frequency equivalent to the frequency of 2, the generation of a failure diagnosis signal from the failure diagnosis signal generator is prohibited, and when the signal to be processed does not have a frequency equivalent to the second frequency, late A signal for failure diagnosis is generated from the signal generator for diagnosis, the output signal from the signal processing unit is frequency-analyzed, the signal for failure diagnosis is determined, and the signal processing unit based on the determined signal for failure diagnosis Determine the failure.
[0017]
A part of the first frequency band of the normal processing signal is set as a failure diagnosis signal frequency (second frequency). The failure diagnosis unit, based on the diagnosis signal from the frequency classification unit, detects a failure diagnosis signal from the failure diagnosis signal generation unit when a target peak signal having a frequency near the second frequency is not detected in the normal processing signal. Is superimposed on the normal processing signal.
[0018]
The failure diagnosis unit performs failure diagnosis based on the signal in the vicinity of the second frequency from the frequency sorting unit. When a failure is detected, this is communicated to the host system.
[0019]
With the above configuration, it is not necessary to switch the connection between the normal signal generation unit and the failure diagnosis signal generation unit for the signal processing unit (circuit to be diagnosed) and perform diagnosis while executing normal processing functions. It is possible to realize a signal processing device with a failure diagnosis function that can be performed.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
In addition, the example demonstrated below is an example of the millimeter wave radar apparatus using the analog signal processing circuit of 2 frequency CW (Continuous Wave) type millimeter wave radar.
[0021]
First, an outline of a general millimeter wave radar apparatus will be described with reference to FIG.
The millimeter wave radar device 1 is attached in front of the host vehicle 15. The millimeter wave radar 1 includes a transmission control unit 3, and a modulation signal for switching two frequencies is generated and output from the transmission control unit 3.
[0022]
The modulation signal output from the transmission control unit 3 is supplied to the oscillator 4. The oscillator 4 generates an electromagnetic wave in the millimeter wave band based on the supplied modulation signal, and the own vehicle 15 via the transmission antenna 5. Send ahead of.
[0023]
When the millimeter wave band electromagnetic wave transmitted from the transmission antenna 5 is reflected by a preceding vehicle, a roadside object, or the like (hereinafter referred to as a target 6), it is received by the reception antenna 7. The reflected wave received by the receiving antenna 7 is mixed with the transmission wave in the mixer 8, thereby converting the frequency from the millimeter wave band frequency to IF (Intermediate Frequency).
[0024]
The sensor includes the transmission control unit 3, the oscillator 4, the antennas 5 and 7, and the mixer 8.
[0025]
A beat signal (sensor signal, signal to be processed of the first frequency) is extracted by mixing of the mixer 8, and the beat signal is amplified by the analog signal processing unit 9. The beat signal amplified by the analog signal processing unit 9 is converted into a digital signal by the A / D converter 10 and subjected to FFT processing in an FFT (Fast Fourier Transform) processing unit 11 to obtain a target peak. . The detailed processing contents of the analog signal processing unit (analog circuit) 9, the A / D converter 10, and the FFT processing unit 11 will be described later.
[0026]
The analog signal processing unit 9 and the A / D converter 10 correspond to a signal processing unit to which a signal to be processed is supplied.
[0027]
The target peak obtained by the FFT processing unit 11 is signal-processed by a target processing unit (information processing unit) 12 to calculate a relative speed, a distance, and an azimuth angle (hereinafter referred to as target information).
[0028]
The target information obtained by the target processing unit 12 is transmitted to a host system 14 such as an ACC (Adaptive Cruise Control) control unit or an inter-vehicle distance alarm unit via a communication driver 13, and is used for vehicle control and driver alarm control. Used.
[0029]
Next, detailed processing contents of the analog signal processing unit 9, the A / D converter 10, and the FFT processing unit 11 will be described with reference to FIGS.
[0030]
FIG. 2 is an internal configuration diagram of the analog signal processing unit 9.
In FIG. 2, the analog signal processing unit 9 includes a preamplifier unit 16, a DC servo unit 17, a demodulation unit 19, an S / H (Sample & Hold) unit 20, and a secondary amplifier unit 21.
[0031]
The beat signal input from the mixer 8 to the analog processing unit 9 is amplified by the preamplifier unit 16. The DC servo unit 17 feeds back the output signal of the preamplifier unit 16 to the input end of the preamble 16 and functions to cancel the DC offset of the beat signal.
[0032]
The signals amplified by the preamplifier unit 16 are superimposed with beat signals (F1, F2) having different phases corresponding to the two transmission frequencies (CF1, CF2) modulated during transmission from the transmission antenna 5. Therefore, the signal amplified by the preamplifier unit 16 is demodulated by the demodulator 19.
[0033]
The two types of beat signals (F1, F2) demodulated by the demodulator 19 are sampled and held by the S / H unit 20, amplified again by the secondary amplifier unit 21, and then A / D converter 10 Is output.
[0034]
FIG. 3 is a waveform diagram for explaining the operations of the A / D converter 10 and the FFT processing unit 11.
FIG. 3A shows the waveform of the beat signal 22 amplified by the secondary amplifier unit 21, where the vertical axis represents signal intensity and the horizontal axis represents time. The beat signal 22 is sampled by the A / D converter 10 at an A / D sampling frequency Fs [Hz] (A / D sampling period T [s] = 1 / Fs), as shown in FIG. Sample data 23 is obtained (in FIG. 3B, the vertical axis represents the signal intensity and the horizontal axis represents the time, as in FIG. 3A).
[0035]
The data sampled by the A / D converter 10 is subjected to FFT processing by the FFT processing unit 11 with the FFT sample point number N as one frame, so that Fs / 2 [Hz as shown in FIG. ] Is obtained as a frequency spectrum 24 of the beat signal with the upper limit of the frequency. In FIG. 3C, the vertical axis represents signal intensity and the horizontal axis represents frequency.
[0036]
One embodiment of the present invention is an example when applied to the above-described millimeter-wave radar device, and this millimeter-wave radar device should be added by paying attention to the fact that the FFT processing unit 11 is provided in advance. A signal processing apparatus with a fault diagnosis function is realized with a minimum number of attached parts.
[0037]
Next, an embodiment of a signal processing apparatus with a fault diagnosis function of the present invention will be described.
FIG. 4 is a schematic configuration diagram of an embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the part same as the part shown in FIG. 1, and the detailed description is abbreviate | omitted.
[0038]
In FIG. 4, the test tone device 2 includes a test tone signal generation unit (second frequency failure diagnosis signal generation unit or diagnosis signal generation circuit) 25 and a test tone peak determination unit 26. FIG. 5 is a diagram illustrating a waveform of the test tone signal output from the test tone signal generation unit 25 and a signal waveform output from the FFT processing unit (frequency separation unit) 11.
The test tone signal generator 25 generates a rectangular wave test tone signal 27 having a frequency Ftt [Hz], a signal intensity A [V], and a duty ratio of 50% shown in FIG. To supply. The analog signal processing unit 9 is also supplied with a beat signal (normal processing signal) output from the mixer 8.
[0039]
In this example, when the total gain of the analog signal processing unit 9 is G and the upper limit signal level of the FFT processing unit 11 is Sth, Ftt <Fs / 2 and G × A <Sth are set. Shall.
[0040]
The test tone signal 27 is superimposed on the beat signal on the input of the preamplifier unit 16 of the analog signal processing unit 9, and the preamplifier unit 16, the demodulator 19, the S / H unit 20, the secondary amplifier unit 21, and the A / D converter 10. To the FFT processing unit 11.
[0041]
In the FFT processing unit 11, a test tone signal having a frequency Ftt superimposed on a signal having a frequency included in the beat signal is obtained. That is, as shown in FIG. 5B, the test tone peak 28 superimposed on the beat signal is obtained.
[0042]
The test tone peak determination unit (failure diagnosis unit) 26 receives the values of the frequency Ftt and the signal strength Stt of the test tone peak 28 from the FFT processing unit 11, and determines whether these values are within a predetermined range. . If the values of the frequency Ftt and the signal strength Stt are not within the predetermined ranges, it is assumed that there is some failure in the analog signal processing unit 9 and that information is transmitted to the host system 14 through the communication driver 13.
[0043]
However, failure determination need not always be performed, and therefore failure determination is performed intermittently with Tt [s] as the failure determination period and Dt [s] as the interval. Further, in order to prevent the target peak from overlapping with the test tone frequency Ftt, it is determined whether or not the frequency Ft of the target peak signal exists within Ft = Fth ± ΔFth1 (within a certain separation range). The test tone peak determination unit 26 does not instruct the test tone signal generation unit 25 to start outputting the test tone signal 27 and does not determine the failure.
Here, Ft is a target frequency, Fth is a reference frequency of the test tone signal, and ΔFth1 is a mixed frequency threshold value.
[0044]
Further, when the noise floor Ntt of the FFT spectrum rises for some reason, the test tone peak is buried in the noise floor Ntt, and even when there is no failure in the analog signal processing unit 9, it may be determined as a failure.
[0045]
In order to avoid this, the test tone peak determination unit 26 does not perform the failure determination when the noise floor Ntt is higher than a certain threshold value Nth.
[0046]
FIG. 6 is an operation flowchart of the test tone apparatus 2. The detailed processing operation of the test tone device 2 will be described based on the operation flowchart shown in FIG.
[0047]
In FIG. 6, first, timers T1 and T2 for managing the failure determination interval Dt and the period Tt are initialized, and measurement of T1 is started (step 601). Next, it waits until T1 becomes Dt (step 602).
[0048]
Next, the target peak and the noise floor are determined (steps 603 and 604). If either of the steps 603 and 604 satisfies the condition for not making a failure determination, that is, if a target peak exists at Ftt ± ΔFth1, or if Ntt> Nth, the process returns to step 601.
[0049]
In steps 603 and 604, if both steps are normal, that is, if the target peak does not exist at Fth ± ΔFth1, and Ntt> Nth is not satisfied, the test tone peak determination unit 26 performs the test. The tone signal generator 25 is instructed to start signal output, starts a timer, starts a timer T2 for monitoring the time from signal output, and starts measuring T2 (step 605).
[0050]
In step 606, it is determined whether or not the measured value of the timer T2 is greater than the failure diagnosis period Tt. If not, the process proceeds to step 607.
[0051]
Next, in step 607, the test tone peak determination unit 26 determines that the measured test tone frequency Ftt and signal strength Stt of the test tone peak 28 are the failure determination criteria (analog signal processing unit 9, A / D converter 10 and Whether or not (a range of values of the diagnostic signal when normal) is satisfied (step 607).
[0052]
If it is determined in step 607 that the failure determination criterion is not satisfied, that is, it can be determined that no failure has occurred (Ftt = Fth ± ΔFth2, Stt = Sth ± ΔSth (dB)), the process returns to step 606. Here, Sth is an allowable reference value of the signal strength Stt, and ± ΔSth is an allowable fluctuation range of the signal strength Stt.
[0053]
In step 606, when the measured value of the timer T2 is larger than the failure diagnosis period Tt, the process proceeds to step 609, the test tone error flag is cleared, and the process returns to step 601. At this time, the generation of the test tone signal from the test tone signal generator 25 is stopped.
[0054]
In step 607, if the failure determination criteria are satisfied, it is determined that a failure has occurred, a test tone error flag is output in step 608, the failure information is transmitted to the host system 14, and the process returns to 601. At this time, the generation of the test tone signal from the test tone signal generator 25 is stopped.
[0055]
As described above, according to one embodiment of the present invention, a part of the frequency Ftt in the frequency band 0 to Fs / 2 of a normal processing signal is used as a signal frequency for failure diagnosis, and the signal for failure diagnosis is It is superimposed on the processing signal. Then, the normal processing signal and the failure diagnosis signal that have passed through the analog processing unit 9 that is the circuit to be diagnosed are supplied to the FFT processing unit 11 via the A / D converter 10 to obtain the frequency spectrum, and for failure diagnosis. The signal is separated from the signal for normal processing. Failure diagnosis is performed based on the sorted failure diagnosis signals. The determination of failure can be made by comparing with the value of the diagnostic signal when the analog signal processing unit 9 and the A / D converter 10 are normal.
[0056]
Further, when the failure diagnosis signal is superimposed on the normal processing signal, the normal processing signal may be in the vicinity of the frequency of the failure diagnosis signal (Fth ± ΔFth1). In this case, the failure diagnosis signal is not generated. It is avoided that the function of processing the normal processing signal is impaired.
[0057]
Therefore, it is not necessary to switch the connection between the normal signal generator and the failure diagnosis signal generator for the circuit to be diagnosed, and the circuit to be diagnosed (analog signal processor 9, It is possible to realize a signal processing device with a fault diagnosis function capable of diagnosing the A / D converter 10).
[0058]
That is, in FIG. 4, whether the signal from the mixer 8 or the signal from the test tone signal generator 25 is input to the analog signal processor 9 between the mixer 8 and the analog signal processor 9. Switching means is unnecessary, and software for controlling the switching operation timing of the switching means is also unnecessary.
[0059]
Since the normal processing signal and the failure diagnosis signal can be superimposed, diagnosis can be performed while executing the normal processing function.
[0060]
In addition, this invention is not limited to the said embodiment, A various change or deformation | transformation can be performed within the scope of the present invention.
[0061]
For example, in the above-described embodiment, FFT processing is used as the signal separation means, but other signal processing means may be used as long as the signal during normal operation and the diagnostic signal can be distinguished.
[0062]
In the above embodiment, the present invention is applied to the millimeter wave radar. However, as long as the elements necessary for the present invention are prepared, the present invention can be applied to other products as well as the radar.
[0063]
For example, the present invention can be applied to failure diagnosis of a device that monitors the flow of products in a factory production line.
[0064]
Other embodiments of the present invention include the following.
The signal from the analog signal processing unit 9 is supplied not only to the A / D converter 10 but also to a band filter (Fth ± (ΔFth + α)) provided separately, and then A / D converted to the test tone peak determination unit 26. Supply. Further, the signal from the A / D converter 10 is supplied not only to the FFT processing unit 11 but also to the test tone peak determination unit 26.
[0065]
Then, based on the signal from the A / D converter 10, the test tone peak determination unit 26 determines whether the frequency Ft of the target peak signal exists at Ft = Fth ± ΔFth1, and whether the noise floor is equal to or less than a predetermined value. Determine whether. When Ft does not exist in Fth ± ΔFth1, a test tone signal is generated, and failure diagnosis is performed based on the diagnostic signal from the separately provided bandpass filter.
[0066]
In this case, the signal from the FFT processing unit 11 need not be supplied to the test tone peak determining unit 26.
[0067]
In FIG. 4, the FFT processing unit 11, the target processing unit 12, and the test tone peak determination unit 26 can be configured by a microprocessor (computer (digital circuit)).
[0068]
In this case, an operation program for operating the computer can be considered. That is, a signal processing unit 9 to which a signal to be processed within a first frequency range obtained from an object is supplied, and a signal processing unit 9 that is superimposed on the signal to be processed and supplied to the signal processing unit 9 and within the first frequency range. A signal processing device with a failure diagnosis function, comprising a failure diagnosis signal generation unit 25 that outputs a failure diagnosis signal of a second frequency and a computer that performs information processing based on an output signal from the signal processing unit 9 It is a computer operating program.
[0069]
This operation program analyzes the frequency of the output signal from the signal processing unit 9, determines whether or not the signal to be processed (output signal from the mixer 8) has a frequency equivalent to the second frequency, When the signal has a frequency equivalent to the second frequency, the generation of the failure diagnosis signal from the failure diagnosis signal generator 25 is prohibited.
[0070]
When the signal to be processed does not have a frequency equivalent to the second frequency, a failure diagnosis signal is generated from the failure diagnosis signal generator 25, and the output signal from the signal processor 9 is frequency-analyzed, Determine the fault diagnosis signal. A failure of the signal processing unit 9 is determined based on the determined failure diagnosis signal.
[0071]
【The invention's effect】
According to the present invention, it is not necessary to switch the connection between the normal signal generation unit and the failure diagnosis signal generation unit for the circuit to be diagnosed, and the diagnosis can be performed while executing the normal processing function. A signal processing apparatus with a fault diagnosis function can be realized.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of a general millimeter wave radar device.
FIG. 2 is a configuration diagram of an analog signal processing unit of the millimeter wave radar device.
FIG. 3 is a waveform diagram for explaining operations of an A / D converter and an FFT processing unit.
FIG. 4 is a schematic configuration diagram of a signal processing apparatus with a fault diagnosis function according to an embodiment of the present invention.
FIG. 5 is a diagram illustrating waveforms of a test tone signal and a test tone peak signal.
FIG. 6 is a signal processing operation flowchart according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Millimeter wave radar apparatus 2 Test tone apparatus 3 Transmission control part 4 Oscillator 5, 7 Antenna 6 Target 8 Mixer 9 Analog signal processing part 10 A / D converter 11 FFT processing part 12 Target processing part 13 Communication driver 14 Host system 15 Self Vehicle 16 Preamplifier unit 17 DC servo unit 19 Demodulation unit 20 S / H unit 21 Secondary amplifier unit 25 Test tone signal generation unit 26 Test tone peak determination unit

Claims (6)

An intermediate frequency signal generated based on a transmission signal and a reception signal received by reflecting the transmission signal on an object is input, and a signal processing unit that generates a frequency spectrum based on the intermediate frequency signal;
The frequency spectrum is input from the signal processing unit, a target processing unit for detecting the object based on a peak appearing in the frequency spectrum,
A diagnostic signal generator for superimposing a predetermined diagnostic signal on the intermediate frequency signal;
When the frequency spectrum is input from the signal processing unit, and there is no peak in the frequency spectrum near the frequency of the diagnostic signal, a diagnostic signal peak determination unit that instructs the diagnostic signal generation unit to superimpose the diagnostic signal When,
A failure determination unit that diagnoses a failure of the signal processing unit based on a peak in the vicinity of the frequency with respect to the diagnostic signal of the frequency spectrum when the diagnostic signal is superimposed on the intermediate frequency signal;
A radar apparatus comprising: A transmission antenna that radiates a transmission signal; and
A receiving antenna that receives a received signal reflected from the object by the transmitted signal;
A mixer that generates an intermediate frequency signal based on the transmission signal and the reception signal;
An analog circuit for processing and outputting the intermediate frequency signal ;
An A / D converter for digitally converting an output signal of said analog circuit,
A digital circuit that performs FFT processing on the intermediate frequency signal converted into a digital value, to generate a frequency spectrum by the A / D converter,
Wherein generating a diagnostic signal for diagnosing the failure of the analog circuit, by superimposing the the diagnostic signal and the intermediate frequency signal, and the diagnostic signal generation circuit for inputting the analog circuit,
When the frequency spectrum is input from the digital circuit and there is no peak in the frequency spectrum near the frequency of the diagnostic signal, a diagnostic signal peak determination unit that instructs the diagnostic signal generation unit to superimpose the diagnostic signal; ,
Wherein when it is superposed to the diagnostic signal into a frequency signal, the frequency spectrum of the diagnostic signal the analog circuit based on a peak frequency near that corresponding to said A / D converter failure determination section determines a failure of equipment When,
A radar apparatus comprising: According to claim 2, wherein the failure determination section, a radar device, characterized in that said analog circuit and the A / D converter performs the failure determination compared with the value of the diagnosis signal when normal. The radar apparatus according to claim 1, wherein the signal processing unit performs an FFT process on the intermediate frequency signal to generate the frequency spectrum. 4. The radar apparatus according to claim 1 , wherein the radar apparatus transmits a radio wave to a front side or a rear side of the vehicle . 6. The radar apparatus according to claim 1, wherein the failure diagnosis is stopped when the noise floor of the spectrum is higher than a predetermined threshold value.

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