JPH07151852A - Fm-cw radar equipment - Google Patents

Abstract

PURPOSE:To detect data on a steady noise component while detecting an object and also to remove the noise component from data on a beat signal generated for detection of the object. CONSTITUTION:A memory 11 which stores and holds spectral distribution data having a spectral level being equal approximately to a preestimated level of a steady noise component or higher than this level, as initial data, a means 15 which compares spectral distribution data on a beat signal obtained at the time of transmission and reception of an electromagnetic wave with the data of the memory 11 at each unit frequency interval and updates the data of the memory 11, using the lower spectral level as the spectral level of the steady noise component at the frequency, and a means 16 which removes the noise component by deducting the updated noise data from the spectral distribution data on the beat signal, are provided. The relative distance D to an object A is determined on the basis of the spectral distribution data on the beat signal wherefrom the noise component is removed.

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, the 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 using a radar device mounted on the own vehicle. In accordance with this, there has been developed a device that maintains the inter-vehicle distance, controls automatic traveling such as braking, and performs various alarms.In this type of radar device, detection of an object at a relatively short distance is performed. An FM-CW radar device is generally used because it is possible and the system configuration is relatively simple.

The detection of the relative distance of an object by the FM-CW radar device is performed as described below, for example.

That is, for example, as shown in FIG. 2, a signal obtained by temporally modulating the frequency in a triangular wave form between frequencies f _X and f _Y is used as a transmission signal and has the same frequency as the transmission signal. While transmitting electromagnetic waves toward the object,
The reflected wave reflected by the object is received. This time,
The received signal of the reflected wave is frequency-modulated into 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 τ.
Of the transmitted and received signals. Therefore, comparing both of the transmitted and received signals on the same time axis,
A frequency difference f _B proportional to the delay time τ is generated. In this case, since the delay time τ is proportional to the relative distance of the target object, the frequency difference f _B is also proportional to the relative distance of the target object, and when the relative distance of the target object is D, the following equation (1) is established. .

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

Based on such a basic principle, the FM-C
The W radar device mixes the transmitted signal and the received signal.
Therefore, the frequency difference f of both signals_BHave a frequency of
A beat signal is generated and the frequency f of the beat signal is generated._BInspect
Put out. Here, the frequency f of the beat signal_BDetection of an example
For example, the period during which both frequencies of the transmitted / received signal increase (Fig.
Reference numeral T in 2_WAnd the frequency of both
In the period in which both decrease, the generated beat signal is F
Arithmetic processing methods such as FT (Fast Fourier Transform) and multiple methods
Frequency analysis using the bandpass filter of
Spectral distribution of the obtained beat signal spectral distribution
By detecting the frequency at which the bell reaches the maximum value
Done. And of the beat signal detected in this way
Frequency f _BFrom the relative distance D of the object according to the equation (1)
Ask for. The FM-CW radar device uses the electromagnetic waves described above.
Wave transmission / reception is repeated periodically as shown in Fig. 2, for example.
While detecting the relative distance D by transmitting and receiving each electromagnetic wave
The relative distance D of the object is detected momentarily.

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

By the way, in this type of FM-CW radar device, generally, the electromagnetic wave transmitted is sneak (a phenomenon in which the electromagnetic wave transmitted from the antenna is directly received by the antenna) and the beat. Due to the frequency characteristics of the amplifier for amplifying the signal, the beat signal includes a frequency component corresponding to the relative distance of the object as well as a stationary noise component (the temporal variation of frequency and level is small. Noise component) is included. For example, the noise component due to the wraparound of the transmitted electromagnetic wave constantly appears in the low frequency region of the spectral distribution of the beat signal. In addition, an amplifier for amplifying a beat signal often has a large gain in a high frequency region in order to extend a detectable relative distance. When such an amplifier is used,
A stationary noise component appears in the low frequency region of the spectral distribution of the beat signal. In addition, a stationary noise component may appear at a predetermined frequency due to the circuit characteristics of the transmitted signal such as the oscillator.

It is unavoidable that such a stationary noise component is superimposed on the beat signal, but the spectral distribution of the beat signal corresponds to the relative distance of the object while the noise component is superimposed. When the frequency to be detected is detected, false detection is likely to occur.

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

That is, the beat signal is generated while transmitting an electromagnetic wave in the direction in which the object does not exist. At this time, since the reflected wave from the object is not received, the generated beat signal is due to a stationary noise component, and by performing frequency analysis on this, the spectral distribution of the stationary noise component can be obtained. Then, when detecting the 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 electromagnetic waves, and thereby the beat signal The stationary noise component is removed from the spectral distribution of. Then, the frequency corresponding to the relative distance of the object is detected from the spectral distribution of the beat signal from which the noise component has been removed in this way.

However, in such a method, until the spectral distribution of the stationary noise component is obtained,
There is an inconvenience that the object cannot be detected and the electromagnetic wave must be transmitted in the direction in which the object does not exist in order to obtain the spectral distribution of the noise component. In particular, immediately after the device is activated, the transmission signal of the electromagnetic wave and the generated beat signal generally become unstable, and it takes time to determine the spectral distribution of the steady noise component. However, the time when the object cannot be detected becomes long. In addition, the frequency and level of steady noise components may fluctuate somewhat due to temperature changes, etc. Therefore, the above processing must be performed at any time, and it is impossible to detect the target object. There is a disadvantage that the number increases.

[0013]

SUMMARY OF THE INVENTION In view of the background described above, the present invention detects a target object, detects stationary noise component data, and generates the noise component for detecting the target object. An object of the present invention is to provide an FM-CW radar device that can be removed from the data of beat signals.

[0014]

In order to achieve the above object, the present invention includes means for repeatedly transmitting an electromagnetic wave whose frequency is temporally modulated, and means for transmitting the electromagnetic wave in the transmitting direction thereof. Means for receiving the reflected wave 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 wave signal of the electromagnetic wave and the received wave signal of the reflected wave; In the FM-CW radar device for detecting the current relative distance of the object from the frequency of the beat signal from which the noise component has been removed. By a frequency analysis of the beat signal generated at the time of transmission of the electromagnetic wave, and a storage means for storing and holding a spectral distribution having a spectral level substantially equal to or higher than the level as the initial data at each unit frequency interval. Frequency analysis means for obtaining a spectral distribution for each unit frequency interval of the beat signal, and the stationary noise component stored and held in the storage means. 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 the data in the storage means with the smaller spectral level as the spectral level of the stationary noise component at the frequency, and the spectral distribution of the stationary noise component updated by the noise data updating means. Noise removing means for obtaining the 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 the 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 To detect 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, the beat signal generated by transmitting / receiving the electromagnetic wave to / from the object includes a frequency component corresponding to the relative distance of the object and a stationary noise component. Although the frequency component corresponding to the frequency and level generally change with the movement of the object,
The frequency and level of stationary noise components 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 means as initial data, and the frequency analysis is performed every time the electromagnetic waves are transmitted and received. The spectrum level at each frequency of the spectrum distribution of the beat signal obtained by the means is compared with the spectrum level of the spectrum of the noise component currently stored and stored in the storage means, and the smaller of the two spectrum levels at each frequency is determined. 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 actual spectrum level of the stationary noise component at the frequency of the stationary noise component is stored in the storage means. Will be stored and stored at, 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,
Finally, the storage means stores and holds the data showing the spectral distribution of the stationary noise component. 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 of the beat signal obtained by transmitting and receiving electromagnetic waves to and from the object. By removing, the spectrum of the stationary noise component is removed from the spectral distribution of the beat signal, and the frequency corresponding to the relative distance of the object is detected based on the spectral distribution of the beat signal from which the noise component has been removed. Then, the relative distance of the object can be obtained from the frequency.

When the counting means is provided,
In the spectral distribution of the beat signal obtained by the frequency analysis means, 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 means, a stationary noise component of the storage means is generated. The data of the spectral distribution of is not updated. This is because when the data in the storage means is updated in such a state,
This is because the data of the spectral distribution of the stationary noise component may be erased.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An example of the present invention will be described with reference to FIGS. 1 is a system configuration diagram of an FM-CW radar device of this 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 for explaining the operation of the radar device of FIG. FIG. 5 is an explanatory diagram for explaining the operation of the radar device of FIG. 1.

Referring to FIG. 1, the FM-CW radar device of the present embodiment is mounted on, for example, an automobile, 1 is an oscillator for generating a transmission signal of an electromagnetic wave, and 2 is a transmitter for generating by the oscillator 1. A modulation control circuit 3 that temporally modulates and controls the frequency of the wave signal is identical to the wave transmission signal in accordance with the wave transmission signal applied from the oscillator 1 through the isolator 4, the directional coupler 5 and the circulator 6. It transmits electromagnetic waves of frequency,
An antenna for receiving the reflected wave of the transmitted electromagnetic wave, 7 is a part of the transmitted signal distributed / input through the directional coupler 5 and the received signal input from the antenna 3 through the circulator 6. And 8 are mixers for generating beat signals having a frequency corresponding to the temporal frequency difference between the two signals, 8 is an amplifier for amplifying the beat signals generated by the mixer 7, and 9 is a beat signal amplified by the amplifier 8. A / D converter for A / D converting 10 is an A / D converter 9
A memory (hereinafter, referred to as a beat signal memory) that stores and holds the beat signal A / D converted by the time series,
Is a memory (storage means, hereinafter referred to as noise memory) for storing and holding the spectral distribution data of stationary noise components included in the beat signal, and 12 is data for the beat signal stored and held in the beat signal memory 10 and the noise memory 11. A signal processing device for detecting the relative distance of the object while detecting the stationary noise component from the stored and held spectral distribution data of the stationary noise component, 13 is an A / D converter 9
The memory 10 and the modulation control circuit 2 respectively provide a timing signal that defines the timing of storing and holding the beat signal A / D converted by the It is a timing signal generation circuit to be given to. still,
The antenna 3 has directivity and transmits an electromagnetic wave toward an object A such as another vehicle in front of the own vehicle. Further, the noise memory 11 includes two storage units 11a and 11b configured by RAM and the like.

The signal processing device 12 is composed of an electronic circuit including a microcomputer, a RAM, a ROM and the like, and the frequency analysis means 1 has a functional structure.
4, noise data updating means 15, noise removing means 16,
The object frequency detection means 17, the distance detection means 18, and the counting means 19 are provided.

Next, the operation of the FM-CW radar device of this embodiment will be described together with a detailed description of each part thereof.

The FM-CW radar system of this embodiment starts its operation by turning on a power source (not shown).
The oscillator 1 generates an electromagnetic wave transmission signal. 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 wave as shown by the solid line in FIG. 2, and the modulation control is output from the timing signal generation circuit 13. According to the timing signal
It is repeated periodically. Then, the transmission signal whose frequency is thus modulated is used as the isolator 4 and the directional coupler 5.
And applied to the antenna 3 via the circulator 6,
As a result, an electromagnetic wave having the same frequency as the transmitted signal and frequency-modulated into a triangular wave is periodically transmitted from the antenna 3 toward the object 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 through the directional coupler 6, and the mixer 7 mixes the transmission signal and the reception signal. To do. As a result, 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 a frequency characteristic such that the gain increases in the high frequency range of the beat signal,
By providing such a frequency characteristic, it is possible to obtain a beat signal having an amplitude level necessary for detecting the relative distance D even when the object A is present at a relatively long distance.

The beat signal amplified by the amplifier 8 is
A / D converter 9 sets A at a predetermined sampling time.
The amplitude data of the beat signal which has been D / D converted and digitized is stored and held in the beat signal memory 10 in time series. In this case, the beat signal memory 10 receives the beat signal within a predetermined period at the time of transmission / reception, every time the transmission / reception of the electromagnetic wave frequency-modulated in the triangular wave is performed according to the timing signal output from the timing signal generation circuit 13. The amplitude data of is stored and held. In this embodiment,
For example, as shown in FIG. 2, the amplitude data of the beat signal is stored and held in the beat signal memory 10 during the period T _W in which both frequencies of the transmitted / received signal increase.

Based on the beat signal data stored and held in the beat signal memory 10 in this way, the signal processing device 12
Thus, the detection process of the relative distance D of the object A and the like are 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 frequency-analyzes the beat signal data stored and held in the beat signal memory 10 to obtain the spectrum distribution thereof. (STEP 1 in FIG. 3). This frequency analysis is performed using, for example, FFT (Fast Fourier Transform method) which is a calculation processing method of frequency analysis. By such frequency analysis, for example, as shown in FIG. 5 (a ₁ ), a spectrum distribution for each unit frequency interval Δf can be obtained. In this case, in the figure, for example, the spectra S _{1 to} S ₄ appear at intervals from the low frequency side to the high frequency side. Of 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 has a peak spectrum level (maximum value) at a frequency f _P corresponding to the relative distance D of the object A.
Appears in the form The spectrum S ₁ on the lowest frequency side shows a steady noise component that appears due to the electromagnetic wave transmitted from the antenna 3 being received by the antenna 3 as it is due to wraparound.
The spectrum S ₂ shows a stationary noise component that appears due to the circuit characteristics of the oscillator 1 and the modulation control circuit 2. In addition, the spectrum S ₄ on the highest frequency side
Shows a stationary noise component that appears due to the frequency characteristics of the gain of the amplifier 8 (characteristic in which the gain increases in the high frequency range) as described above. The unit frequency interval Δf corresponds to the frequency resolution of the beat signal in the device of this embodiment.

Next, the storage section 11a of the noise memory 11
The spectral distribution data of the stationary noise component currently stored and stored in the storage unit 1 (which will be described later) is stored in the storage unit 1.
After being written in 1b (STEP 2 in FIG. 3), the noise removal means 16 of the signal processing device 12 subtracts the spectral distribution data of the stationary noise component stored and held in the storage unit 11b from the spectral distribution data of the beat signal. Then, the spectral distribution of the beat signal from which the stationary noise component is removed is obtained (STEP 3 in FIG. 3).
This subtraction processing subtracts the spectrum level of the stationary noise component at each frequency from the spectrum level of each frequency of the spectrum distribution data of the beat signal (however, when the subtraction result becomes a negative value, it is regarded as "0" level). Be done).

Here, when the apparatus of this embodiment is started, the spectrum distribution data as shown in FIG. 5 (b ₁ ) is previously stored in the storage section 11a of the noise memory 11 as the initial data in the unit frequency interval. It is stored and held for each Δf. The spectrum distribution of the initial data is set so that the spectrum level becomes equal to or higher than the level at which a steady noise component is predicted. The initial data is stored in the storage unit 11b before the removal process is performed.
Written in.

Therefore, when the above-mentioned removal processing is performed,
As shown in FIG. 5 (c ₁ ), all stationary noise components are removed from the beat signal spectral distribution data, and the level of initial data of the stationary noise component spectral distribution is set appropriately. Thus, the peak portion of the spectrum S ₃ corresponding to the reflected wave from the object A can be left.

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 causes the relative distance D of the object A to be detected. Object frequency f _P corresponding to
(See FIG. 5 (c ₁ )) is detected (STEP of FIG. 3)
4). This detection is performed by detecting the 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 the spectrum distribution of the beat signal obtained by removing the stationary noise component. Done.

Then, the signal processing device 12 obtains the relative distance D of the object A by the distance detecting means 18 from the object frequency f _p detected as described above according to the equation (1), and this is not shown. It is output to the automatic traveling control device, the alarm device, etc. (STEP 5 in FIG. 3).

On the other hand, in parallel with the processing for detecting the relative distance D of the object A as described above, after the data in the storage section 11a of the noise memory 11 is written in the storage section 11b as described above, the above-mentioned FIG. Using the spectral distribution data of the beat signal obtained in STEP 1 of
By the noise data updating means 15 of No. 2, the noise memory 1
The data of the storage unit 11a of No. 1 is updated (STE of FIG. 3).
P8). Prior to this, in the spectrum distribution data of the beat signal, a determination process is performed as to whether or not there are a predetermined number or more of frequencies at which the spectrum level becomes 0 level (STEPs 6 and 7 in FIG. 3). Will be described later.

The data in the storage section 11a of the noise memory 11 is updated as follows.

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

[0036] With this updating process, FIG. 5 (a _1),
From the spectrum distribution data of (b ₁ ), the spectrum distribution data of the noise component as shown in (b ₂ ) of the same figure is obtained, and this is newly stored and held in the storage unit 11 a. That is, the spectra S ₁ , S ₂ , S ₄ corresponding to stationary noise components are stored and held in the storage unit 11a. The spectral distribution of FIG. 5 (b ₂ ) is shown in FIG.
Since it is obtained from the spectral distribution data of (a ₁ ) and (b ₁ ), it is not the original stationary noise component at the frequency position corresponding to the spectrum S ₃ corresponding to the object A of FIG. 5 (a ₁ ). The spectrum S ₅ remains, but such a spectrum S ₅ disappears as will be described later.

In the FM-CW radar device of this embodiment, basically, the operation described above is performed every time new beat signal data is stored and held in the beat signal memory 10 (each transmission / reception of an electromagnetic wave). 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. Then, by repeating the updating process of the noise data as described above, only the actual spectrum distribution data of the stationary noise component will be stored and held in the storage unit 11a of the noise memory 11 in due course.

That is, the noise data update process is repeated.
In the process of returning,₂)
Spectrum S that is not a normal noise component_FiveIs a noise memo
Items that may be stored and held in the storage unit 11a of the memory 11
Such a spectrum S _FiveRepeat the above update process
By returning it, it will be removed eventually.

More specifically, the spectrum S_FiveIs a figure
5 (a₁) Spectral distribution of the first beat signal shown in
Spectrum S corresponding to object A in the data₃When,
Figure 5 (b₁) Of the noise component spectral distribution shown in
Although it was obtained from the
A corresponds to the object A because it moves with respect to the own vehicle
Spectrum S₃The frequency at which the
₂), (A₃) It changes as shown in. For this reason,
Spectrum S that is not a noise component_FiveFrequency f _FiveOke
The spectral level of the beat signal is
₂), It becomes 0 level,
When updating the noise data as described above,
The space newly stored in the storage unit 11a of the memory 11 is held.
The cuttle distribution data is shown in Fig. 5 (b).₃) As shown above
Wave number f_FiveData that becomes 0 level at the position
As a result, in the storage unit 11a of the noise memory 11,
Is only the spectral distribution data of stationary noise component
It will be held in memory. And after that, noise
Component spectrum S₁, S₂, S_FourFrequencies other than
In terms of numbers, 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 and held in the storage unit 11a is the data of the embodiment.
Shows the spectral distribution of stationary noise components in
It will be decided as a thing. In addition, FIG.₂),
(C₃) Are respectively shown in FIG.₂), (A₃) Beat
From the spectrum distribution data of the signal, FIG.₂),
(B₃) The spectral distribution data of the noise component of
Spectral distribution data obtained by
As mentioned above, the object frequency is
It is detected and the relative distance is determined.

By the way, as described above, when updating the noise data, 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 steady noise component spectra S ₁ and S _{2 are obtained.} , S ₄ when the spectrum level becomes 0 level in the frequency range in which they originally appear, a situation occurs in which the stationary noise component spectrum distribution data stored and held in the storage unit 11a of the noise memory 11 is erased.

Therefore, in order to avoid such a situation in the FM-CW radar device of this embodiment, first, the signal processing device 1 is performed before the above-mentioned noise data updating process.
In the spectrum distribution data of the beat signal, the second counting means 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 0 level (FIG. 3).
STEP 6). Then, when the number N of frequencies at which the spectrum level becomes 0 level is equal to or more than a predetermined number (YES in STEP 7 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 can be avoided. still,
When the number N of frequencies at which the spectrum level becomes 0 level is less than the predetermined number (N in STEP 7 of FIG.
O), the noise data update process is performed as described above.

As described above, the FM-C of this embodiment
In the W radar device, the detection of the relative distance D of the object A and the detection processing of the spectral distribution data of the stationary noise component can be efficiently performed in parallel, and the relative distance D of the object A can be detected. Is basically detected by removing the beat signal or the stationary noise component, 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 device is shown in FIG.
Although it is set as shown in (b ₁ ), a spectral distribution that more closely approximates the predicted spectral distribution of the noise component may be set as the initial data. Then, in such a case, the spectrum distribution data of the noise component stored and held in the storage unit 11a of the noise memory 11 immediately before the operation of the present device is stopped is set as the initial data when the device is started next time. Good. With this configuration, it is possible to detect the relative distance of the object by removing the stationary noise component with relatively high accuracy immediately after the device is started except when the device is first started. It is also possible to set the spectrum distribution data of the beat signal obtained at the first time immediately after the device is activated as the initial data.

Further, in the present embodiment, after the steady spectral distribution data of the noise component is almost determined in one operation of the device, the spectral distribution data of the noise component is not reduced unless the spectral level of the noise component is lowered. Is almost never updated, but even when the device is operated once, the oscillator 1
Storage unit 11a of the noise memory 11 according to the temperature change of the
May be rewritten to the initial data at the time of startup. In this way, even if the spectral distribution of the stationary noise component may change due to the temperature change of the oscillator 1 or the like, the spectral distribution data of the changed noise component can be obtained.

Further, in the present 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 previous transmission / reception of the electromagnetic wave is used. However, the subtraction process 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 spectral level at each frequency of the spectral distribution of the stationary noise component stored and held in the storage means is the beat obtained when transmitting and receiving the electromagnetic wave. Comparing with the spectrum level of the spectrum distribution of the signal, the smaller spectrum level of the two spectrum levels at each frequency is used as the spectrum level of the stationary noise component at the frequency, and the data in the storage means is updated and stored. Detection of the target object by subtracting the spectral distribution data of the noise component stored and held in the means from the spectral distribution data of the beat signal and determining the relative distance of the target object from the spectral distribution of the beat signal from which the noise component has been removed While detecting the stationary noise component data, The noise component can be removed from the data of the beat signal generated for detecting 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. It is possible to detect the target object with high accuracy.

In the spectral distribution of the beat signal, the noise data is not updated at the time of abnormality such that the frequency at which the spectral level becomes 0 level exceeds a predetermined number, so that the steady spectrum of the noise component is obtained. It is possible to avoid a situation where the distribution data is deleted from the storage means.

[Brief description of 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.

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

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

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

[Explanation of symbols]

11 ... Storage means, 14 ... Frequency analysis means, 15 ... Noise data updating means, 16 ... Noise removing means, 17 ... Object frequency detecting means, 19 ... Counting means.

Claims (2)

[Claims] 1. 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 the transmitting direction when the electromagnetic wave is transmitted, and the electromagnetic wave. 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 wave and the received signal of the reflected wave; And means for removing noise components,
In an FM-CW radar device that detects the current relative distance of the object from the frequency of the beat signal from which the noise component has been removed, a spectral level that is approximately equal to or higher than the expected level of the stationary noise component. A storage unit that stores and holds the spectral distribution having the following as initial data at each unit frequency interval, and performs a frequency analysis on the beat signal generated at the time of transmitting the electromagnetic wave to obtain a spectral distribution for each unit frequency interval of the beat signal. And a spectrum level at each frequency of the spectrum distribution of the stationary noise component stored and held in the storage means and a 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 in the storage means by setting the level to the spectral level of the stationary noise component at the frequency, and at each frequency of the spectral distribution of the stationary noise component updated by the noise data updating means. Noise removing means for obtaining the spectral distribution of the beat signal from which the noise component has been removed by subtracting the spectral level from the spectral level at each frequency of the spectral distribution of the beat signal obtained by the frequency analyzing means, and the noise removing 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 object from the frequency detected by the object frequency detection means FM-C characterized by detecting relative distance Radar device. 2. The spectrum level at each frequency of the spectrum distribution of the beat signal obtained by the frequency analysis means is compared with 0 level, and the spectrum level is 0.
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 more than a predetermined number. The FM-CW radar device according to claim 1.