JP2793487B2 - FM-CW radar device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an FM-CW radar device.

[0002]

2. Description of the Related Art In recent years, for example, in an automobile, a relative distance of an object such as another vehicle existing in front of or behind the own vehicle with respect to the own vehicle is detected by using a radar device mounted on the own vehicle. In response to this, automatic cruise control such as maintaining the inter-vehicle distance, braking, etc., and various alarms have been developed, and in this type of radar device, detection of an object at a relatively short distance has been developed. FM-CW radar devices are generally used because they are possible and the system configuration is relatively simple.

[0003] The detection of the relative distance and the like of an object by the FM-CW radar apparatus is performed, for example, as described below.

That is, as shown in FIG. 2, for example, a signal obtained by temporally modulating the frequency between a frequency f _X and a frequency f _{Y in} a triangular waveform is used as a transmission signal and has the same frequency as the transmission signal. While transmitting electromagnetic waves toward the object,
A reflected wave reflected by the object is received. At this time,
The received signal of the reflected wave is frequency-modulated in the form of a triangular wave like the transmitted signal, but the time τ required to reciprocate between the antenna transmitting and receiving the electromagnetic wave and the object is
Is generated with respect to the transmitted signal, and therefore, when the transmitted and received signals are compared on the same time axis, there is a delay between the two signals.
Resulting in the frequency difference f _B which is proportional to the delay time tau. In this case, since the delay time τ is proportional to the relative distance of the object, the frequency difference f _B is also proportional to the relative distance of the object, and if the relative distance of the object is D, the following equation (1) holds. .

D = k · f _B (1) In the equation (1), k is the propagation speed (light speed) of the electromagnetic wave;
This is a constant determined by the temporal change rate of the frequency of the transmitted / received signal.

[0006] Based on such a basic principle, FM-C
The W radar device mixes a transmitted signal and a received signal.
Thus, the frequency difference f between the two signals is obtained._BHaving a frequency of
Generate a beat signal and generate a frequency f of the beat signal._BDetect
Put out. Here, the frequency f of the beat signal_BDetection is an example
For example, the period during which both frequencies of the transmitted and received signals increase (see
2, reference symbol T_WAnd the frequency of both are
In the period in which both are reduced, the generated beat signal is
Arithmetic processing methods such as FT (fast Fourier transform method)
Frequency analysis using the band pass filter of
Spectrum of the obtained beat signal
By detecting the frequency at which the bell has a maximum value,
Done. And the beat signal detected in this way
Frequency f _BFrom the above equation (1), the relative distance D of the object is
Ask for. The FM-CW radar device uses the electromagnetic
Wave transmission / reception is periodically repeated as shown in FIG. 2, for example.
Of relative distance D by transmission and reception of each electromagnetic wave
And the relative distance D of the object is detected every moment.

Since the relative speed of the object is obtained by temporally differentiating the relative distance D of the object, the temporal change rate of the relative distance D detected for each transmission / reception of the electromagnetic wave is calculated as described above. If determined, the relative speed of the object can be detected.

By the way, in this type of FM-CW radar device, in general, the electromagnetic wave transmitted (the phenomenon that the electromagnetic wave transmitted from the antenna is directly received by the antenna) or the beat Due to the frequency characteristics of the amplifier for amplifying the signal, the beat signal includes not only a frequency component corresponding to the relative distance of the target object but also a stationary noise component (frequency and level temporal fluctuations are small. Noise component). For example, a noise component due to the wraparound of the transmitted electromagnetic wave constantly appears in the low frequency region of the spectrum distribution of the beat signal. In addition, an amplifier for amplifying a beat signal often increases the gain in a high-frequency region in order to extend a detectable relative distance, and when such an amplifier is used,
A stationary noise component appears in the low frequency region of the spectrum distribution of the beat signal. In addition, a stationary noise component may appear at a predetermined frequency due to circuit characteristics such as an oscillator of a transmission signal.

It is inevitable that such a stationary noise component is superimposed on the beat signal. However, with such a noise component superimposed on the beat signal, the noise component corresponding to the relative distance of the object can be obtained from the spectral distribution of the beat signal. When a frequency is detected, erroneous detection is likely to occur.

For this reason, it is preferable to remove a stationary noise component from the beat signal by some method. For example, the following method can be considered.

That is, the beat signal is generated while transmitting an electromagnetic wave in a direction in which no object exists. At this time, since the reflected wave from the target is not received, the generated beat signal is due to a stationary noise component, and a frequency distribution of the generated beat signal provides a stationary noise component spectrum distribution. When detecting an object, as described above, the spectrum level of the stationary noise component is subtracted from the spectrum level at each frequency of the spectrum distribution of the beat signal obtained by transmitting and receiving the electromagnetic wave, thereby obtaining the beat signal. Stationary noise components are removed from the spectral distribution of. Then, the frequency corresponding to the relative distance of the target is detected from the spectrum distribution of the beat signal from which the noise component has been removed.

However, in such a method, until a steady noise component spectrum distribution is obtained,
There is an inconvenience that an object cannot be detected and that an electromagnetic wave must be transmitted in a direction in which the object does not exist in order to obtain a spectral distribution of the noise component. In particular, immediately after the start-up of the apparatus, generally, the transmission signal of the electromagnetic wave and the generated beat signal become unstable, and it takes time to determine the spectrum distribution of the steady noise component. Therefore, the time during which the detection of the target object cannot be performed becomes long. In addition, the frequency and level of the stationary noise component may fluctuate slightly due to temperature changes and the like. Therefore, the above-described processing must be performed at any time, and the object cannot be detected. However, there is an inconvenience that the number increases.

[0013]

SUMMARY OF THE INVENTION In view of this background, the present invention detects stationary noise component data while detecting an object and generates the noise component for object detection. It is an object of the present invention to provide an FM-CW radar device that can remove from beat signal data.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a means for repeatedly transmitting an electromagnetic wave whose frequency has been modulated in time, and an electromagnetic wave which exists in the transmitting direction when the electromagnetic wave is transmitted. Means for receiving reflected waves from the object,
Means for generating a beat signal having a frequency corresponding to the current relative distance of the object by mixing a part of the transmitted signal of the electromagnetic wave and the received signal of the reflected wave; Means for removing a static noise component, wherein the FM-CW radar apparatus detects the current relative distance of the object from the frequency of the beat signal from which the noise component has been removed. Storage means for storing and maintaining a spectrum distribution having a spectrum level substantially equal to or higher than the level to be performed at each unit frequency interval as initial data, and frequency-analyzing the beat signal generated at the time of transmitting the electromagnetic wave, Frequency analysis means for obtaining a spectrum distribution of the beat signal for each unit frequency interval; The spectrum level in each frequency spectrum distribution as compared with the spectrum level of the spectral distribution of the beat signal obtained by the frequency analyzing means, out of the two spectra level at each frequency,
Noise data updating means for updating data in the storage means with a smaller spectrum level as a spectrum level of a stationary noise component at the frequency; and a spectrum distribution of the stationary noise component updated by the noise data updating means. Noise removing means for obtaining a spectral distribution of the beat signal from which the noise component has been removed by subtracting the spectral level at each frequency from the spectral level at each frequency of the spectral distribution of the beat signal obtained by the frequency analyzing means, Object frequency detecting means for detecting a frequency corresponding to the relative distance of the object based on the spectral distribution of the beat signal obtained by the noise removing means, and from the frequency detected by the object frequency detecting means Detecting the relative distance of the object. And butterflies.

Further, there is provided counting means for comparing the spectrum level at each frequency of the spectrum distribution of the beat signal obtained by the frequency analysis means with 0 level, and counting the number of frequencies at which the spectrum level becomes 0 level. The noise data updating means does not update the data in the storage means when the number counted by the counting means is a predetermined number or more.

[0016]

According to the present invention, a beat signal generated by transmitting and receiving an electromagnetic wave to and from the object includes a stationary noise component together with a frequency component corresponding to the relative distance of the object. Although the frequency component corresponding to generally changes its frequency and level with the movement of the object, etc.,
The frequency and level of the stationary noise component do not change much. Therefore, a spectrum distribution having a spectrum level substantially equal to or higher than the actual level of the stationary noise component is stored and held in the storage unit as initial data, and the frequency analysis is performed every time the electromagnetic wave is transmitted and received. The spectrum level at each frequency of the spectral distribution of the beat signal obtained by the means is compared with the spectral level of the spectral distribution of the noise component currently stored in the storage means, and the smaller one of the two spectral levels at each frequency is obtained. When the data in the storage means is updated with the spectrum level as the spectrum level of the stationary noise component at the frequency, the spectrum level of the actual stationary noise component is stored at the frequency of the stationary noise component. At other frequencies, and at other frequencies Although temporarily there is the spectral level of the frequency components corresponding to the relative distance of the object remains, eventually becomes substantially 0 level, thereby,
Eventually, the storage means stores and holds data indicating a steady noise component spectrum distribution. Then, the spectrum level at each frequency of the spectrum distribution of the stationary noise component of the storage means obtained by such updating is subtracted from the spectrum level of the spectrum distribution of the beat signal obtained by transmitting and receiving electromagnetic waves to and from the object. As a result, the spectrum of the stationary noise component is removed from the spectrum distribution of the beat signal, and the frequency corresponding to the relative distance of the object is detected based on the spectrum distribution of the beat signal from which the noise component has been removed. Thus, the relative distance of the object can be obtained from the frequency.

When the counting means is provided,
In the spectrum distribution of the beat signal obtained by the frequency analysis unit, when the number of frequencies at which the spectrum level becomes 0 level becomes a predetermined number or more due to an abnormality of the frequency analysis unit or the like, a steady noise component of the storage unit. Is not updated. This is because when updating the data in the storage means in such a state,
This is because there is a possibility that data of the spectrum distribution of the stationary noise component is erased.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One example of the present invention will be described with reference to FIGS. 1 is a system configuration diagram of the FM-CW radar device according to the present embodiment, FIG. 2 is an explanatory diagram for explaining the operation of the radar device of FIG. 1, and FIGS. 3 and 4 are diagrams illustrating the operation of the radar device of FIG. FIG. 5 is an explanatory diagram for explaining the operation of the radar apparatus of FIG.

Referring to FIG. 1, the FM-CW radar apparatus according to the present embodiment is mounted on, for example, an automobile. Reference numeral 1 denotes an oscillator for generating a transmission signal of an electromagnetic wave, and reference numeral 2 denotes a transmission generated by the oscillator 1. The modulation control circuit 3 modulates and controls the frequency of the wave signal with time, and the modulation control circuit 3 uses the same transmission signal according to the transmission signal provided from the oscillator 1 via the isolator 4, the directional coupler 5, and the circulator 6. Transmits electromagnetic waves of frequency,
An antenna 7 receives the reflected wave of the transmitted electromagnetic wave, and 7 is a part of the transmission signal distributed and input via the directional coupler 5 and a reception signal input from the antenna 3 via the circulator 6. And a mixer for generating a beat signal having a frequency corresponding to the temporal frequency difference between the two signals, an amplifier for amplifying the beat signal generated by the mixer, and a beat signal amplified by the amplifier A / D converter for A / D conversion of A / D converter 10 is an A / D converter 9
(Hereinafter referred to as a beat signal memory) for storing and holding the beat signal A / D converted in time series
Is a memory (storage means, hereinafter referred to as a noise memory) for storing and holding the spectrum distribution data of the stationary noise component included in the beat signal, and 12 is a memory for the beat signal stored in the beat signal memory 10 and the noise memory 11. A signal processing device 13 for detecting the relative distance of the target object while detecting the stationary noise component from the spectral distribution data of the stationary noise component stored and held; 13 is an A / D converter 9
And a modulation control circuit 2 that respectively specify a timing signal for defining the timing of storing and storing the beat signal A / D-converted in the beat signal memory 10 and a timing signal for defining the transmission timing of the frequency-modulated electromagnetic wave. Is a timing signal generation circuit to be added to the timing signal. still,
The antenna 3 has directivity, and transmits an electromagnetic wave toward an object A such as another vehicle existing in front of the own vehicle, for example. Further, the noise memory 11 includes two storage units 11a and 11b each configured by a RAM or the like.

The signal processing device 12 is composed of an electronic circuit including a microcomputer, a RAM, a ROM, and the like.
4, noise data updating means 15, noise removing means 16,
An object frequency detecting unit 17, a distance detecting unit 18 and a counting unit 19 are provided.

Next, the operation of the FM-CW radar apparatus according to the present embodiment will be described together with the detailed description of each part thereof.

The FM-CW radar apparatus of this embodiment starts operation by turning on a power source (not shown).
The oscillator 1 generates a transmission signal of an electromagnetic wave. At this time, the frequency of the transmission signal generated by the oscillator 1 is modulated by the modulation control circuit 2 into a triangular waveform as shown by the solid line in FIG. According to the timing signal
It is repeated periodically. The transmission signal whose frequency has been modulated in this way is supplied to the isolator 4 and the directional coupler 5.
And provided to the antenna 3 via the circulator 6,
Thereby, the electromagnetic wave having the same frequency as the transmission signal and frequency-modulated in a triangular wave shape is periodically transmitted from the antenna 3 toward the target A existing in front of the vehicle.

At the time of transmitting such an electromagnetic wave, the reflected wave from the object A is received by the antenna 3, and the received signal is input to the mixer 7 via the circulator 6. At this time, a part of the transmission signal output from the oscillator 1 is distributed and input to the mixer 7 via the directional coupler 6, and the mixer 7 mixes the transmission signal and the reception signal. I do. Thereby, as described above, basically, a beat signal having a frequency corresponding to the relative distance D of the object A to the own vehicle is generated.

The beat signal generated by the mixer 7 is amplified by the amplifier 8 to a required amplitude level. In this case, the amplifier 8 has frequency characteristics such that the gain increases in the high frequency range of the beat signal.
By providing such frequency characteristics, even if the object A is relatively distant, a beat signal having an amplitude level necessary for detecting the relative distance D can be obtained.

The beat signal amplified by the amplifier 8 is
The A / D converter 9 sets the A at every predetermined sampling time.
The / D-converted and digitized amplitude data of the beat signal is stored in the beat signal memory 10 in time series. In this case, each time the transmission and reception of the triangular-wave-frequency-modulated electromagnetic wave is performed in accordance with the timing signal output from the timing signal generation circuit 13, the beat signal memory 10 stores the beat signal within a predetermined period during the transmission and reception. Is stored. In this embodiment,
For example the frequency of both the transmitting and receiving wave signals are both stores and holds the amplitude data of the beat signal to the beat signal memory 10 during the period T _W is increased as shown in FIG.

Based on the beat signal data stored and held in the beat signal memory 10 as described above, the signal processing device 12
As a result, a process of detecting the relative distance D of the target A is performed as described below.

That is, referring to the flowchart of FIG. 3, first, the frequency analysis means 14 of the signal processing device 12 analyzes the frequency of the beat signal data stored and held in the beat signal memory 10, and obtains the spectrum distribution. (Step 1 in FIG. 3). This frequency analysis is performed using, for example, FFT (Fast Fourier Transform method), which is an arithmetic processing method of frequency analysis. By such a frequency analysis, for example, as shown in FIG. 5 (a ₁ ), a spectrum distribution for each unit frequency interval Δf is obtained. In this case, in the figure, for example, spectra S _{1 to} S ₄ appear at intervals from the low frequency side to the high frequency side, and among these spectra S _{1 to} S ₄ , the spectrum S ₃ is the object A. It corresponds to the received signal of the reflected wave from
The spectrum S ₃ are spectrum level peaks at the position of the frequency f _P corresponding to the relative distance D of the object A (maximum value)
Appears in such a way that Further, the spectrum S ₁ on the lowest frequency side shows a stationary noise component which appears due to the fact that the electromagnetic wave transmitted from the antenna 3 is received by the antenna 3 as it is due to the wraparound.
Further, the spectrum S ₂ shows a stationary noise component appearing due to the circuit characteristics such as the oscillator 1 and the modulation control circuit 2. Also, the spectrum S ₄ on the highest frequency side
Indicates a stationary noise component appearing due to the frequency characteristic of the gain of the amplifier 8 (a characteristic in which the gain increases in a high frequency range) as described above. The unit frequency interval Δf corresponds to the frequency resolution of the beat signal in the device of the present embodiment.

Next, the storage unit 11a of the noise memory 11
The stationary noise component spectrum distribution data (which will be described later) currently stored and held in the storage unit 1
After the data is written in 1b (STEP 2 in FIG. 3), the noise removal means 16 of the signal processing device 12 subtracts the spectrum distribution data of the stationary noise component stored and held in the storage unit 11b from the spectrum distribution data of the beat signal. As a result, a spectral distribution of the beat signal from which a stationary noise component has been removed is obtained (STEP 3 in FIG. 3).
In this subtraction processing, the spectrum level of the stationary noise component at that frequency is subtracted from the spectrum level of each frequency of the spectrum distribution data of the beat signal (however, if the subtraction results in a negative value, the level becomes “0” level). To do).

[0029] Here, at the time of startup of the device of the present embodiment, the noise in the storage unit 11a of the memory 11, the unit frequency interval spectrum distribution data as shown in advance for example FIG. 5 (b ₁₎ is as initial data It is stored and held for each Δf. The spectral distribution of the initial data is set so that its spectral level is equal to or higher than the level at which the stationary noise component is predicted. The initial data is stored in the storage unit 11b before the withdrawal processing is performed.
Is written to.

Therefore, when the above-mentioned withdrawal processing is performed,
As shown in FIG. 5 (c ₁ ), all the stationary noise components are removed from the beat signal spectral distribution data, and the level of the initial data of the stationary noise component spectral distribution is set appropriately. it is, it is possible to leave the peak portions of the spectrum S ₃ corresponding to the reflected wave from the object a.

Next, based on the spectral distribution of the beat signal obtained by removing the stationary noise component as described above, the object frequency detecting means 17 of the signal processing device 12 detects the relative distance D of the object A. Object frequency f _P corresponding to
(See FIG. 5 (c ₁ )) is detected (STEP in FIG. 3).
4). This detection is performed by detecting a frequency at which the spectrum level changes from an increasing tendency to a phenomenon tendency, that is, a frequency at which the spectrum level has a maximum value, in a spectrum distribution of a beat signal obtained by removing a stationary noise component. Done.

[0032] Then, the signal processing device 12 the distance detecting means 18 calculates the relative distance D of the object A according to the equation from the detected object frequency f _p (1) as described above, not shown this The information is output to an automatic traveling control device, an alarm device, and the like (STEP 5 in FIG. 3).

On the other hand, in parallel with the process of detecting the relative distance D of the object A, as described above, after the data of the storage unit 11a of the noise memory 11 is written to the storage unit 11b, as shown in FIG. Using the spectral distribution data of the beat signal obtained in STEP 1 of FIG.
2 by the noise data updating means 15
3 is updated (STE in FIG. 3).
P8). Prior to this, in the spectrum distribution data of the beat signal, it is determined whether or not the frequency at which the spectrum level becomes 0 level is equal to or more than a predetermined number (STEPs 6 and 7 in FIG. 3). Will be described later.

Updating of data in the storage section 11a of the noise memory 11 is performed as follows.

That is, FIGS. 4 and 5 (a ₁ ),
With reference to (b ₁ ), the spectrum distribution data of the beat signal obtained by the frequency analysis means 14 and the spectrum distribution data of the stationary noise component written in the storage unit 11b of the noise memory 11 are the same. From the lowest frequency f ₀ to the highest frequency f _{end of the} spectrum distribution data
And the respective spectral levels L _B (f) and L _N (f) at each frequency for each unit frequency interval Δf
Is compared with the spectrum level L _B (f) of the beat signal.
Is smaller than the spectrum level L _N (f) of the noise component currently stored and held in the storage unit 11a, the spectrum level L _B (f) of the beat signal is used as the spectrum level of the noise component at that frequency.
The data of 1a is updated. And if not (L
_{For B} (f) ≧ L _N (f)), the data in the storage unit 11a at that frequency is not updated, but remains as it is.

By the updating process, FIG. 5 (a ₁ ),
From the spectrum distribution data of (b ₁ ), spectrum distribution data of the noise component as shown in FIG. ₂ (b ₂ ) is obtained, and this is newly stored and held in the storage unit 11 a. That is, the spectra S ₁ , S ₂ , and S ₄ corresponding to stationary noise components are stored and held in the storage unit 11a. Incidentally, the spectral distribution of FIG. 5 (b ₂₎ is 5
_{(A 1), (b 1} ) for obtained from the spectral distribution data, not the original steady noise component at the location of the frequency corresponding to the spectrum S ₃ corresponding to the object A in FIG. 5 (a ₁₎ so that the spectrum S ₅ remains, but such spectral S ₅ is disappear soon as will be described later.

In the FM-CW radar apparatus of the present embodiment, basically, the above-described operation is performed every time new beat signal data is stored in the beat signal memory 10 (for each transmission and reception of electromagnetic waves). 2), and the process of detecting the relative distance D of the object A and the process of constantly updating the spectral distribution data of the noise component are repeated in parallel. By repeating the above-described noise data update processing, the storage unit 11a of the noise memory 11 eventually stores only the actual steady-state noise component spectrum distribution data.

That is, the updating process of the noise data is repeated.
In the process of returning, FIG._Two), As shown in
Spectrum S that is not a normal noise component_FiveIs a noise memo
What may be stored and held in the storage unit 11a of the file 11
Of such a spectrum S _FiveRepeats the above update process
By returning, it will be eventually removed.

More specifically, the spectrum S_FiveThe figure
5 (a₁) Spectrum distribution of the first beat signal shown in)
Spectrum S corresponding to object A in the data_ThreeWhen,
FIG.₁The first of the spectral distributions of the noise components shown in
Period data, but in general,
A corresponds to the target A because it moves with respect to the own vehicle
Spectrum S_ThreeAppearing in FIG. 5 (a)
_Two), (A_Three). For this reason,
Spectrum S not noise component_FiveFrequency f _FiveSmell
5 (a).
_Two), As shown in FIG.
Performing the noise data update process as described
The space newly stored in the storage unit 11a of the memory 11 is stored.
Fig. 5 (b)_Three) As shown above
Wave number f_FiveData that is 0 level at the position
As a result, the storage unit 11a of the noise memory 11
Is only the spectral distribution data of the stationary noise component
It will be stored. And then the noise
Component spectrum S₁, S_Two, S_FourFrequencies other than
In the number, the spectrum other than the noise component is stored in the storage unit 1.
1a is not stored and held in the noise memory 11
The data stored in the storage unit 11a is stored in the storage device of this embodiment.
Shows the spectrum distribution of stationary noise components
Will be determined. In addition, FIG._Two),
(C_Three) Respectively correspond to FIG._Two), (A_Three) Beat
From the spectrum distribution data of the signal, FIG._Two),
(B_Three) Subtract the noise component spectrum distribution data
The spectrum distribution data obtained from
From the spectral distribution data, the target frequency is
It is detected and a relative distance is obtained.

When the noise data is updated as described above, the spectrum distribution data of the beat signal cannot be normally obtained due to an abnormality of the mixer 7 or the like. For example, the spectrums S ₁ and S _{2 of} stationary noise components are not obtained. , the spectrum level is 0 level in the frequency range in which S ₄ appears inherently situation that the spectral distribution data for stationary noise component that has been stored and held in the storage unit 11a of the noise memory 11 is erased occurs.

Therefore, in the FM-CW radar apparatus of the present embodiment, in order to avoid such a situation, before performing the above-described noise data update processing, first, the signal processing apparatus 1
In the spectral distribution data of the beat signal, the count level 19 compares the spectrum level with the 0 level at each unit frequency interval Δf, and counts the number N of frequencies at which the spectrum level becomes the 0 level (FIG. 3).
STEP6). Then, when the number N of frequencies at which the spectrum level becomes 0 level is equal to or greater than a predetermined number (YES in STEP7 of FIG. 3),
The above-described noise data update processing (STEP 8 in FIG. 3) is not performed, and the data currently stored and held in the storage unit 11a of the noise memory 11 is left as it is. By doing so, the above inconvenience is avoided. still,
When the number N of frequencies at which the spectrum level becomes the 0 level is less than the predetermined number (in STEP 7 of FIG.
O) As described above, the noise data updating process is performed.

As described above, the FM-C of this embodiment
In the W radar device, the detection of the relative distance D of the target A and the detection processing of the spectrum distribution data of the stationary noise component can be efficiently performed in parallel. Is basically performed by removing a beat signal or a stationary noise component, so that the relative distance D
Can be accurately detected.

In this embodiment, the initial data of the spectral distribution of the noise component at the time of starting the apparatus is shown in FIG.
Although set as shown in (b ₁ ), a spectral distribution that more closely approximates the spectral distribution of the predicted noise component may be set as the initial data. In such a case, the spectrum distribution data of the noise component stored in the storage unit 11a of the noise memory 11 is set as the initial data at the time of the next startup of the apparatus immediately before the operation of the apparatus is stopped this time. Is also good. This makes it possible to detect the relative distance of the target object with relatively accurate removal of the stationary noise component immediately after the apparatus is started, except for the first time the apparatus is started. It is also possible to set, as initial data, the spectrum distribution data of the beat signal obtained the first time immediately after the activation of the device.

Also, in this embodiment, after the spectrum distribution data of the stationary noise component is almost fixed in one operation of the apparatus, the spectrum distribution data of the noise component is not changed unless the spectrum level of the noise component decreases. Is rarely updated. However, even during a single operation of the device, the periodical or oscillator 1
Storage unit 11a of the noise memory 11 according to the temperature change of the
May be rewritten to, for example, initial data at the time of startup. In this way, even if the spectrum distribution of the stationary noise component changes due to the temperature change of the oscillator 1 or the like, the spectrum distribution data of the changed noise component can be obtained.

In this embodiment, when the spectral distribution data of the noise component is subtracted from the spectral distribution data of the beat signal, the spectral distribution data of the noise component obtained at the time of the previous transmission and reception of the electromagnetic wave is used. However, the above-described subtraction processing may be performed after updating the spectral distribution data of the noise component.

[0046]

As is apparent from the above description, according to the present invention, the spectrum level at each frequency of the steady noise component spectrum distribution stored and stored in the storage means is obtained by the beat obtained when the electromagnetic wave is transmitted and received. The data is compared with the spectrum level of the spectrum distribution of the signal, and the smaller of the two spectrum levels at each frequency is updated as the spectrum level of the stationary noise component at the frequency, and the data in the storage unit is updated. Detecting the object by subtracting the spectral distribution data of the noise component stored in the means from the spectral distribution data of the beat signal and obtaining the relative distance of the object from the spectral distribution of the beat signal from which the noise component has been removed. While detecting stationary noise component data The noise component can be removed from the data of the beat signal generated for the detection of the target object, and the stationary noise component detection process and the relative distance detection process of the target object are efficiently performed in parallel. In addition, the object can be accurately detected.

The noise data is not updated at the time of occurrence of an abnormality in which the frequency at which the spectrum level becomes 0 level or more occurs in the spectrum distribution of the beat signal. A situation in which distribution data is deleted from the storage means can be avoided.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of an example of an FM-CW radar device of the present invention.

FIG. 2 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

FIG. 3 is a flowchart for explaining the operation of the radar device of FIG. 1;

FIG. 4 is a flowchart for explaining the operation of the radar device of FIG. 1;

FIG. 5 is an explanatory diagram for explaining the operation of the radar device of FIG. 1;

[Explanation of symbols]

11 ... storage means, 14 ... frequency analysis means, 15 ... noise data update means, 16 ... noise removal means, 17 ... object frequency detection means, 19 ... count means.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G01S 13/34 G01S 7/292

Claims (2)

(57) [Claims] A means for repeatedly transmitting an electromagnetic wave whose frequency is temporally modulated; a means for receiving a reflected wave from an object existing in a transmitting direction of the electromagnetic wave when the electromagnetic wave is transmitted; Means for generating a beat signal having a frequency corresponding to the current relative distance of the object by mixing a part of the transmitted signal of the reflected wave and the received signal of the reflected wave; Means for removing a noise component,
In an FM-CW radar device for detecting a current relative distance of the object from a frequency of a beat signal from which the noise component has been removed, a spectrum level substantially equal to or higher than an expected level of the stationary noise component Storage means for storing and holding the spectrum distribution having the following at each unit frequency interval as initial data, and frequency analysis of the beat signal generated at the time of transmission of the electromagnetic wave to obtain a spectrum distribution of the beat signal at each unit frequency interval. Frequency analysis means for obtaining, and comparing the spectrum level at each frequency of the spectrum distribution of the stationary noise component stored and held in the storage means with the spectrum level of the spectrum distribution of the beat signal obtained by the frequency analysis means. , The smaller of the two spectral levels at each frequency Noise data updating means for updating the data of the storage means as a level of a spectrum level of a stationary noise component at the frequency; and at each frequency of the spectrum distribution of the stationary noise component updated by the noise data updating means. Noise removing means for obtaining a spectral distribution of a beat signal from which the noise component has been removed by subtracting a spectral level from a spectral level at each frequency of a spectral distribution of the beat signal obtained by the frequency analyzing means; Object frequency detection means for detecting a frequency corresponding to the relative distance of the object based on the spectral distribution of the beat signal obtained by the, the frequency of the object from the frequency detected by the object frequency detection means FM-C characterized by detecting relative distance Radar device. 2. The method according to claim 1, wherein a spectrum level at each frequency of a spectrum distribution of said beat signal obtained by said frequency analysis means is compared with 0 level,
Counting means for counting the number of frequencies that become levels, wherein the noise data updating means does not update the data in the storage means when the number counted by the counting means is equal to or greater than a predetermined number. The FM-CW radar device according to claim 1, wherein