JP3353765B2 - FMCW radar self-diagnosis system and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an on-vehicle FMCW radar. In particular, the present invention relates to a self-diagnosis system and method for an FMCW (Frequency Modulation Continuous Wave) radar that self-diagnoses whether or not the radar is operating normally.

[0002]

2. Description of the Related Art FIG. 8 shows an inter-vehicle distance to a preceding vehicle during traveling.
FIG. 9 is a diagram for describing an example of measuring a relative speed. As shown in the figure, an FMCW radar mounted on an automobile irradiates a radar beam to a preceding vehicle, receives a reflected wave, and measures an inter-vehicle distance and a relative speed with the preceding vehicle.

In an FMCW radar, a local signal sent from a high-frequency signal oscillator frequency-modulated by a triangular wave is amplified, radiated as a transmission signal to a preceding vehicle, and is reflected by a target of the preceding vehicle. You. The received signal of the reflected wave and the local signal sent from the high-frequency signal oscillator are mixed to form a beat signal, and the beat signal is processed to determine an inter-vehicle distance and a relative speed with a preceding vehicle. In this way, if the laser beam is irradiated and the inter-vehicle distance and the relative speed with respect to the preceding vehicle are obtained, it is possible to confirm that the operation is normal.

[0004]

However, if the vehicle is not running ahead, there is no target for the FMCW radar and there is no reflected wave.
The relative speed cannot be obtained. If this situation continues, there is a problem that anxiety arises that the FMCW radar may be out of order.

For this reason, it is necessary to perform self-diagnosis as to whether the vehicle is operating normally when the preceding vehicle is not running, and to eliminate the fear of failure. When realizing such a self-diagnosis, diagnosis can be performed while driving, so that processing can be performed in a short period of time. Since the FMCW radar is mounted on a car, the installation location is limited, so that the size can be reduced, and the cost increase must be suppressed. There is a problem that must be. Therefore,
The present invention has been made in view of the above-described problems, and is capable of performing processing in a short time, being compact, suppressing an increase in cost, and having high reliability.
It is an object of the present invention to provide an MCW radar self-diagnosis system and method.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention is directed to a self-diagnosis system for an FMCW radar which irradiates a target with a radar beam and receives a reflected wave. A transmission amplifier that amplifies a local signal and serves as a transmission signal, a duplexer that separates an amplified transmission signal and a reception signal amplified by the transmission amplifier, and a local signal that is sent from a high-frequency signal oscillator. A reception mixer that mixes the reception signal to form a beat signal, and a leakage signal and a high-frequency signal of the amplified transmission signal that are separated by the demultiplexer in the reception mixer when the object is not present. When storing the level of a nearby noise signal of the transmission signal formed by mixing with the local signal sent from the oscillator and stopping the operation of the transmission amplifier A data memory for storing the level of the noise signal output from the receiving mixer, and comparing the level of the near-noise signal stored in the data memory with the level of the noise signal to determine whether the FMCW radar has failed A self-diagnosis system for an FMCW radar, comprising: Preferably, the duplexer is a circulator, and more preferably, a semiconductor switch.

By this means, it is possible to make a self-diagnosis as to whether or not the vehicle is operating normally when the preceding vehicle is not running, to eliminate anxiety about failure of the FMCW radar, and to shorten the time. Processing can be performed in a short time, the device can be compact, the increase in cost can be suppressed, and the reliability can be increased.

Preferably, the self-diagnosis unit determines that a difference between the level of the near noise signal and the level of the noise signal is a first difference.
Is determined to be larger than a predetermined value, and if it is larger, self-diagnosis is made that there is no failure. More preferably, the self-diagnosis unit determines whether or not the absolute value of the level of the nearby noise signal is greater than a second predetermined value.

By this means, reliability for a predetermined value can be ensured. Preferably, a coil is provided in the circulator, and a magnetic field is generated in the coil, so that isolation in a reverse direction is reduced and a level of a leakage signal related to a transmission signal of the circulator is increased.
By this means, the level of the leakage signal is increased, the influence of the outside can be eliminated, the erroneous level determination of the leakage signal due to other noise can be prevented, and the reliability with respect to the predetermined value can be ensured.

Preferably, when the object is present, the level of the beat signal of the receiving mixer is stored in the data memory as the level of the near noise signal. By this means, self-diagnosis becomes possible even when there is an object. Preferably, the self-diagnosis unit determines whether or not there is an object based on whether or not the distance to the object and the relative speed are obtained from the beat signal of the receiving mixer.

By this means, the presence or absence of an object can be easily determined, and self-diagnosis can be automatically performed when there is no object. Further, the present invention provides a method for self-diagnosis of an FMCW radar which irradiates a target with a radar beam and receives a reflected wave, wherein the step of amplifying the transmission signal and the step of demultiplexing the amplified transmission signal and the reception signal are performed. Mixing the local signal sent from the high-frequency signal oscillator with the received signal to form a beat signal; and when the target is absent, the leak signal and the high-frequency signal of the separated amplified transmission signal. The level of a noise signal near the transmission signal formed by mixing with the local signal sent from the signal oscillator is stored, and the noise signal obtained by the mixing process when the operation of amplifying the transmission signal is stopped. Storing a level, and comparing the stored level of the nearby noise signal with the level of the noise signal to determine whether the FMCW radar has failed. Providing a self-diagnostic system for FMCW radar, characterized in that it comprises a step of performing self-diagnosis.

By this means, it is possible to perform self-diagnosis as to whether or not the vehicle is operating normally when the preceding vehicle is not running, as in the above-described invention, and it is possible to eliminate anxiety about failure of the FMCW radar. , And can be processed in a short time.
Reliability can be increased.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a schematic configuration of a self-diagnosis system in an in-vehicle FMCW radar according to the present invention. As shown in this figure, FMC
The W radar is provided with a high-frequency signal oscillator 1, and the high-frequency signal oscillator 1 generates a millimeter-wave high-frequency (RF) signal.

A control circuit 8 is connected to the input of the high-frequency signal oscillator 1.
Is connected, the control circuit 8 causes the high-frequency signal oscillator 1 to perform triangular wave modulation, and causes the high-frequency signal oscillator 1 to oscillate in a frequency sweep. The output of the high-frequency signal oscillator 1 is connected to the transmission amplifier 2 and the reception mixer 3. The transmission amplifier 2 amplifies the oscillation signal of the high-frequency signal oscillator 1 to form a transmission signal.

A circulator 4 is connected to an output of the transmitting amplifier 2 and an input of the receiving mixer 3, and an antenna 4 is connected to the circulator 4. The circulator 4 receives a transmission signal from the transmission amplifier 2 and
, And a received signal (RF) is input from the antenna 5,
The antenna 5 that outputs to the receiving mixer 3 converts the transmission signal input from the circulator 4 into a transmission wave, receives the reflected wave, converts it into a reception signal, and outputs it to the circulator 4.

When a radar beam is radiated from the antenna 5 facing the forward vehicle, the transmitted wave propagates in the air and is reflected by the forward vehicle, which is the target of the radar. The reflected wave propagates through the air again, returns to the antenna 5, and is received by the antenna 5. Note that the local signal of the triangular wave modulation signal of the high-frequency signal oscillator 1 is swept more than the received signal by the propagation time when the radar beam travels from the antenna 5 to the vehicle in front and is reflected by the vehicle in front and returns to the antenna 5. I have. Therefore, a frequency difference occurs between the local signal and the received signal due to the air propagation time of the transmitted wave and the received wave.

The receiving mixer 3 mixes the local signal from the high-frequency signal oscillator 1 and the received signal from the circulator 4 to form a beat signal. The frequency band of the beat signal is up to several hundred KHz. This beat signal is formed by the frequency difference between the local signal and the received signal. A reception signal amplifier 6 is connected to the output of the reception mixer 3, and the reception signal amplifier 6 amplifies the beat signal.

The reception signal amplifier 6 is provided with a signal processing circuit 7, and the signal processing circuit 7 processes the amplified beat signal to determine the inter-vehicle distance and the relative speed with the preceding vehicle. In the processing of the signal processing circuit 7, usually, a beat signal is converted from analog to digital, a fast Fourier transform or the like is performed, a frequency of the beat signal is obtained, and an inter-vehicle distance and a relative speed are obtained in consideration of the Doppler effect. I have.

By the way, when there is no vehicle ahead while traveling, there is no radar object, and there is no received wave with respect to the transmitted wave propagating in the air. In this case, a signal output from the transmission amplifier 2 to the reception system leaks to the reception mixer 3 without partly going to the antenna 5 as isolation loss due to reverse rotation of the circulator 4. When an object is present and a received wave is present, this leakage is ignored because the level is small.

There is a demand for miniaturization, low cost, and the like of FMCW radars for use in vehicles, and from this demand, at present, transmission and reception isolation cannot be expected much. Therefore, in the present invention, a transmission leakage signal that appears due to insufficient isolation between transmission and reception is actively used.

When there is no received wave, the leakage signal from the circulator 4 and the local signal of the high-frequency signal oscillator 1 are signals having substantially the same frequency. Only the nearby noise signal of the transmission signal remains and is formed as an output signal of the reception mixer 3. FIG. 2 is a diagram illustrating waveforms of a transmission signal, a reception signal, a beat signal, and a leakage signal.

As shown in FIG. 2A, the transmission signal is a triangular wave modulation signal, and the local signal of the high-frequency signal oscillator 1 is transmitted only during the time when the radar beam is irradiated, reflected by the object, and propagated in the air. The frequency sweeps more than the received signal. As shown in FIG. 2B, when a received wave is present, a beat signal between the local signal of the high-frequency signal oscillator 1 and the received signal is present at the output of the receiving mixer 3. As shown by the dotted line in FIG. 3C, when no received wave is present, no beat signal between the local signal of the high-frequency signal oscillator 1 and the received signal is present in the output of the receiving mixer 3, and the DC component is not present. And a nearby noise signal of the transmission signal.

The signal processing circuit 7 is provided with a self-diagnosis unit 7A. The self-diagnosis unit 7A inputs a DC component signal of the reception mixer 3 via the reception signal amplifier 6 and performs a self-diagnosis process. . Further, the transmission amplifier 2 has a switch 2A.
The switch 2A is controlled by the self-diagnosis unit 7A, and temporarily stops the supply of the power supply voltage of the transmission amplifier 2.

Further, a data memory 9 is provided in the signal processing circuit 7, and the data memory 9 stores the signal level of the DC component from the receiving mixer 3 under the control of the self-diagnosis unit 7A. First, in the data memory 9, the signal level La of the DC component due to the leakage signal when the object does not exist and the received wave does not exist is stored as the noise level.

Next, the data memory 9 stores the signal level Lb of a signal in which the switch 2A of the transmitting amplifier 2 is temporarily disconnected and no leakage signal exists. The level Lb of this signal is a noise level caused by thermal noise of the reception mixer 3 and the like. This noise is processed as a noise level via the reception signal amplifier 6. The self-diagnosis unit 7A compares these La and Lb. If the level difference is larger than a predetermined value (Δ1), the self-diagnosis unit 7A diagnoses that the receiving system is operating normally, and determines that the level difference is the predetermined value. If smaller, it is diagnosed that one of the receiving system and the transmitting system is not operating normally.

If one of the receiving system and the transmitting system does not operate, no signal leaks to the receiving system and the level difference becomes small. FIG. 3 is a diagram for explaining a series of operations relating to the self-diagnosis system of the FMCW radar. As shown in the figure, in step S101, it is confirmed that the high-frequency signal oscillator 1 is operating.

In step S102, it is confirmed that the receiving mixer 3, the receiving signal amplifier 6, and the signal processing circuit 7 are operating and in a receiving state. In step S103, it is confirmed that the transmission amplifier 2 is operating by closing the switch 2A. In this case, the high-frequency signal amplified by the transmission amplifier 2 is sent to the antenna 5 via the circulator 4.

Therefore, a transmission wave is radiated from the antenna 5 into the air. Normally, a radar beam emitted into the air is directed at a radar object and returns as a reflected wave.

When there is no received wave in the air that is a reflected wave from the object, the signal output from the transmitting amplifier 2 is output to the receiving system as an isolation loss due to the reverse rotation of the circulator 4. Leak to mixer 3.

In the FMCW radar shown in FIG. 1, the leaked transmission signal substantially appears as a DC voltage and a noise signal near the transmission signal as shown in FIG. This appears quantitatively when transmission and reception are performed by the same antenna because transmission and reception isolation exist at a certain level. In step S104, the level of the nearby noise signal of the transmission signal is processed by the next-stage reception signal amplifier 6 and the self-diagnosis unit 7A of the signal processing circuit 7, and is determined as the noise level La when there is no object.

In step S105, the noise level La is stored in the data memory 9, and the process proceeds to step S109.
Send to In step S106, the self-diagnosis unit 7A disconnects the switch 2A to temporarily stop the operation of the transmission amplifier 2. In this case, since there is no signal leakage from the transmission system, the output of the receiving mixer 3 has a noise level such as thermal noise of the mixer itself.

In step S107, this noise level is also processed by the next-stage reception signal amplifier 6 and the self-diagnosis unit 7A of the signal processing circuit 7, and the noise level L of only the reception system is obtained.
b is determined. In step S108, the noise level Lb is stored in the data memory 9 and sent to step S109.

In step S109, step S1
05, the noise levels La and Lb stored in the data memory 9 in step S108 are taken out, and a noise level difference is obtained in order to compare these noise levels. In step S110, it is determined whether the noise level difference is equal to or greater than a predetermined level.

In step S111, if the noise level difference is equal to or more than a predetermined level, it is diagnosed that transmission and reception are operating normally. In step S112,
If the noise level difference is less than a predetermined level, the transmission system,
Diagnose that one or both of the receiving systems are not operating.
Further, even if there is a reflected object of the radar during the self-diagnosis operation, it is merely stored in the data memory 9 as the value of the reception level during the transmission operation, and the level is higher than the noise level. Diagnosis is possible. Therefore, self-diagnosis can be performed without selecting a measurement place.

Therefore, according to the present invention, the self-diagnosis of the FMCW radar is instantaneous (several milliseconds) by comparing the reception noise level when the transmission system is operating and when it is not operating.
In addition, it is possible with a simple configuration, without requiring an extra installation place and without choosing a measurement place.

In the above description, the circulator 4 is used as a splitter of the antenna 5, but the present invention is not limited to this, and a similar effect can be obtained by using a semiconductor switch. This is because transmission and reception interference can be used. Further, in the above description, the magnitude of the noise level difference between ON / OFF of the switch 2A of the transmission amplifier 2 is used as a criterion for the self-diagnosis. However, when the switch 2A of the transmission amplifier 2 is ON, the absolute value of the noise level becomes Even if the self-diagnosis is performed based on whether the value is larger than the predetermined value (Δ2), the same operation and effect can be obtained.

Next, the self-diagnosis was performed based on the leakage signal of the transmission signal due to the isolation loss of the circulator 4 in the reverse direction. However, if the reception level fluctuates due to the entry of an external disturbance, the self-diagnosis is not performed. Become stable. Therefore, the reliability of the determination is improved as described below.

FIG. 4 is a diagram showing a modification of FIG. As shown in the figure, the circulator 4 is provided with a coil 4A, the coil 4A is provided with a switch 4B, and the switch 4B for driving the coil 4A is opened and closed as compared with FIG. It is controlled by the self-diagnosis unit 7A. The coil 4A is located either above or below the circulator 4, and generates a magnetic field to reduce the reverse isolation of the circulator 4 and increase the level of the leakage signal of the transmission signal. For this reason, the noise level increases, and the reliability of the self-diagnosis can be increased as the determination value.

FIG. 5 shows the circulator 4 and the coil 4 shown in FIG.
FIG. 6 is an assembled perspective view showing the relationship with A, and FIG. 6 is a cross-sectional view showing the relationship between the circulator 4 and the coil 4A in FIG. As shown in FIGS. 5 and 6, the magnetic field of the radio wave input to one terminal of the circulator 4 is perpendicular to the traveling direction of the strip line 41, and when passing through the ferrite 43, the polarization plane rotates due to the Faraday effect. .

The coil 4A temporarily applies a DC magnetic field H0 opposite to the magnetic field formed by the ferrite 43 from the outside to temporarily weaken the magnetic field of the ferrite 43. FIG. 7 is a diagram for explaining reduction of isolation in the reverse direction in the circulator 4. As shown in the figure, due to the DC magnetic field H0 of the coil 4A, the transmission loss of the transmission signal in the direction toward the antenna 5 increases, and the isolation of the transmission signal in the reverse direction to the receiving mixer is reduced. As a result, the near noise signal of the transmission signal actively leaks to the receiving mixer 3 more, and is sent to the receiving mixer 3 as a leaked signal.

In this way, the level of the nearby noise signal of the transmission signal can be increased as shown by the solid line in FIG.
This makes it possible to avoid erroneous determination of the level determination relating to the noise that is the output of, and to secure the stability of the self-diagnosis determination and improve the reliability. When the circulator 4 is sufficiently isolated, the level of the nearby noise signal fluctuates due to external influence as shown by the dotted line in FIG.

[0042]

As described above, according to the present invention,
Self-diagnosis can be performed by comparing the noise level of the reception system due to the operation of the transmission system and the non-operation of the FMCW radar, and the target that is the original operation of the radar is irradiated with the radar beam to check the normal operation. Self-diagnosis is now easier than performing diagnostic work.

Further, since the self-diagnosis is performed when the object is not required, it is possible to eliminate anxiety that a failure has occurred when data on the following distance and the relative speed are not processed. In addition, in a short time, compactly and at low cost,
The self-diagnosis can be performed with high reliability, and the self-diagnosis can be performed even during the time of actual operation, and the self-diagnosis can be performed regardless of a measurement place.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of a self-diagnosis system in an on-vehicle FMCW radar according to the present invention.

FIG. 2 is a diagram illustrating waveforms of a transmission signal, a reception signal, a beat signal, and a leakage signal.

FIG. 3 is a diagram illustrating a series of operations related to a self-diagnosis system of the FMCW radar.

FIG. 4 is a diagram showing a modification of FIG. 1;

FIG. 5 is an assembled perspective view showing a relationship between the circulator 4 and a coil 4A in FIG. 4;

FIG. 6 is a sectional view showing a relationship between the circulator 4 and a coil 4A in FIG.

FIG. 7 is a diagram illustrating reduction of isolation in the reverse direction in the circulator 4.

FIG. 8 is a diagram for explaining an example of measuring an inter-vehicle distance and a relative speed with a preceding vehicle during traveling.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 high-frequency signal oscillator 2 transmission amplifier 2A, 4B switch 3 reception mixer 4 circulator 4A coil 5 antenna 6 reception signal amplifier 7 signal processing circuit 7A self-diagnosis unit 8 control circuit 9 Data memory 41 ... Strip line 42 ... Substrate 43 ... Ferrite 44 ... Ground plate

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (9)

(57) [Claims] An FMCW radar self-diagnosis system for irradiating a target with a radar beam and receiving a reflected wave, comprising: a transmission amplifier that amplifies a local signal sent from a high-frequency signal oscillator and uses it as a transmission signal; A duplexer for splitting an amplified transmission signal and a reception signal amplified by a transmission amplifier; and a reception mixer for forming a beat signal by mixing a local signal sent from a high-frequency signal oscillator and the reception signal. And transmission formed by mixing the leakage signal of the amplified transmission signal split by the splitter and the local signal sent from the high-frequency signal oscillator in the reception mixer when the object is not present. A level of a noise signal output from the reception mixer when the operation of the transmission amplifier is stopped is stored. And a self-diagnosis unit that compares the level of the noise signal and the level of the noise signal stored in the data memory and performs self-diagnosis of whether or not the FMCW radar has failed. A self-diagnosis system for FMCW radar. 2. The self-diagnosis system for an FMCW radar according to claim 1, wherein the duplexer is a circulator. 3. The self-diagnosis system for an FMCW radar according to claim 1, wherein the duplexer is a semiconductor switch. 4. The self-diagnosis unit determines whether a difference between the level of the nearby noise signal and the level of the noise signal is greater than a first predetermined value, or determines whether a difference between the level of the first predetermined value and Judge whether the level is within the predetermined value of
The self-diagnosis system for an FMCW radar according to claim 1, wherein the self-diagnosis is performed when there is no failure when the value is within a predetermined value. 5. The self-diagnosis unit determines whether or not the absolute value of the level of the nearby noise signal is larger than a second predetermined value, and if the absolute value is larger, performs a self-diagnosis that there is no failure. The self-diagnosis system for an FMCW radar according to claim 1, wherein 6. A circulator is provided with a coil, and a magnetic field is generated in the coil, so that isolation in a reverse direction is reduced and a level of a leakage signal related to a transmission signal of the circulator is increased. The self-diagnosis system of the FMCW radar according to claim 2. 7. The data processing apparatus according to claim 1, wherein a level of a beat signal of a receiving mixer is stored in the data memory as the level of the near noise signal when the object is present.
4. A self-diagnosis system for an FMCW radar according to 4. 8. The self-diagnosis unit determines whether or not there is an object based on whether or not a distance to the object and a relative speed are obtained from a beat signal of a receiving mixer.
The FMCW radar self-diagnosis system according to claim 1. 9. A self-diagnosis method for an FMCW radar, which irradiates a target with a radar beam and receives a reflected wave, comprising the steps of: amplifying a local signal sent from a high-frequency signal oscillator to obtain a transmission signal; A step of demultiplexing the amplified transmission signal and the reception signal; a step of mixing the local signal sent from the high-frequency signal oscillator with the reception signal to form a beat signal; The level of a nearby noise signal of a transmission signal formed by mixing a leak signal of a filtered amplified transmission signal and a local signal sent from a high-frequency signal oscillator is stored, and the operation of amplifying the transmission signal is temporarily performed. Storing the level of the noise signal obtained by the mixing process when the operation is stopped, and the stored level of the near noise signal and the level of the noise signal. Self-diagnosis method of FMCW radar, characterized in that it comprises a step of comparing the bell performs self-diagnosis of whether the FMCW radar is faulty.