JPH0643236A - Input abnormality protective circuit for on-vehicle radar equipment - Google Patents

Abstract

(57) [Abstract] [Purpose] An input abnormality protection circuit for an in-vehicle radar device that protects the in-vehicle radar device against excessive input or under-input, and protects the FET used in a low noise amplifier from deterioration or destruction. Or to inform the driver of an abnormality in the on-vehicle radar device. [Configuration] When the abnormal input determination means 2 determines an excessive input, the protection means 3 takes measures to protect the in-vehicle radar device. Specifically, by the drain voltage reducing means 3a,
The drain voltage of the FET is reduced to reduce the gain of the FET, or the transmission output reduction means 3b reduces the transmission-side output of the vehicle-mounted radar device. Further, when the abnormal input discriminating means 2 discriminates the excessive input, the notifying means 4
Informs the driver of the abnormality of the on-vehicle radar device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input abnormality protection circuit for an on-vehicle radar device, and more particularly to an input abnormality protection circuit for an on-vehicle radar device which takes measures such as protection of the on-vehicle radar device against excessive input or under-input.

In recent years, as a collision prevention radar for automobiles,
In-vehicle radar devices using radio waves such as millimeter waves have been developed. With this device, a frequency-modulated signal such as a millimeter wave is emitted to a vehicle ahead or a stationary object in the vicinity, and based on the reflected wave that is reflected and returned, the relative speed or distance of the vehicle with respect to the vehicle ahead or the vehicle itself. Calculate the speed of the car and the distance to a stationary object,
When it senses a danger, it alerts the driver or controls the braking of the vehicle.

[0003]

2. Description of the Related Art Conventionally, in a vehicle-mounted radar device, a reflection signal such as a millimeter wave is received by a receiving antenna, and a low noise amplifier (L
NA (low noise amplifier) is used for high frequency amplification, and then frequency conversion and the like are performed. A FET (field effect transistor) amplifier is usually used as a low noise amplifier, and a HEMT (high electron
mobility transistor) is used. By using this HEMT, the low noise performance of the low noise amplifier is improved and the economy is improved.

[0004]

By the way, the signal level of the reflected wave changes depending on the distance of the own vehicle to the vehicle in front or the stationary object, and also greatly changes depending on weather conditions and environmental conditions.

For this reason, when the signal level input to the receiving antenna becomes, for example, too high, the FET used in the low noise amplifier is deteriorated or destroyed, and conversely becomes too low. In this case, an input signal of a predetermined level or higher is not input to the mixer for frequency conversion, which causes malfunctions in the millimeter wave circuit, causing the on-vehicle radar device to malfunction and hinder safe driving. There was a problem.

The present invention has been made in view of the above circumstances, and protects the FET used in the low noise amplifier from deterioration and destruction, and notifies the driver of an abnormality of the on-vehicle radar device. An object is to provide an input abnormality protection circuit for an on-vehicle radar device.

[0007]

FIG. 1 is a diagram for explaining the principle of the present invention proposed to achieve the above object.

As shown in the figure, the input abnormality protection circuit of the on-vehicle radar device of the present invention detects the signal level of the reflected wave and outputs it, and abnormal input according to the magnitude of the output of the detection means 1. The abnormal input discriminating means 2 and the protecting means 3 for protecting the on-vehicle radar device when the abnormal input discriminating means 2 discriminates an excessive input.

Further, the on-vehicle radar device has a low noise amplifier (LNA) using an FET, and the protection means 3 reduces the drain voltage of the FET when the abnormal input discrimination means 2 discriminates an excessive input. It comprises a voltage reducing means 3a. Reducing the drain voltage also includes setting the drain voltage to zero and turning off the FET.

Further, the protection means 3 is an abnormal input determination means 2
Is composed of transmission output reducing means 3b for reducing the output on the transmission side of the in-vehicle radar device when the excessive input is discriminated. Also,
The input abnormality protection circuit of the on-vehicle radar device of the present invention includes a detection unit 1 that detects and outputs a signal level of a reflected wave, and an abnormality input determination unit 2 that determines an abnormal input according to the magnitude of the output of the detection unit 1. The abnormal input discriminating means 2 comprises a notifying means 4 for notifying when the abnormal input is discriminated.

The detecting means 1 comprises a gate current detecting means 1a for detecting and outputting the gate current of the FET. Further, the detection means 1 is composed of a detection voltage detection means 1b which detects and outputs a detection voltage.

[0012]

In the above structure, the detecting means 1 detects the signal level of the reflected wave and outputs it to the abnormal input discriminating means 2.
The abnormal input discriminating means 2 discriminates the abnormal input according to the magnitude of the output of the detecting means 1. If the input is a normal level within a predetermined range, the input signal is sent to the signal processing circuit after high-frequency amplification and frequency conversion, and the relative speed and distance of the own vehicle to the preceding vehicle, or the speed of the own vehicle and the distance to the stationary object. Etc. are calculated.

However, if the abnormal input discriminating means 2 discriminates an excessive input, the protecting means 3 takes measures to protect the on-vehicle radar device. Specifically, the drain voltage reducing means 3a reduces the drain voltage of the FET,
The output of the on-vehicle radar device is reduced by reducing the gain of the FET or by the transmission output reduction means 3b. In this way, the FE used in the low noise amplifier
Protect T from deterioration and destruction.

Further, if the abnormal input discriminating means 2 discriminates the excessive input, the informing means 4 informs the driver of the abnormality of the on-vehicle radar device. As a result, the driver switches to driving without depending on the on-vehicle radar device.

As the detecting means 1 for detecting and outputting the signal level of the reflected wave, there are a gate current detecting means 1a and a detected voltage detecting means 1b. Gate current detecting means 1a
Detects and outputs the gate current flowing through the gate of the FET. Further, the detection voltage detection means 1b detects a signal input to the FET or a signal output from the FET, detects the detection voltage, and outputs the detected voltage.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a block circuit diagram showing the configuration of the on-vehicle radar device. In the figure, the modulation signal frequency-modulated by the FM modulator 11 is converted into a millimeter wave of 60 GHz by the voltage controlled oscillator 12 and output from the transmitting antenna 13. The transmitting antenna 13 has a strong directivity and is emitted toward a target.

The reflected wave reflected by the target object is received by the receiving antenna 14, and the received signal is input to the low noise amplifier (LNA) 15. Low noise amplifier (LN
A) A switching signal generator 16 that generates a 1 MHz pulse is connected to A) 15 via a switching transistor 17, and a low noise amplifier (LNA) 15 is 60 GH.
The amplified signal of z + 1 MHz is output to the mixer 18. A signal of 60 GHz on the transmission side is input to the mixer 18 via the directional coupler 19, and therefore 1 M
The Hz signal is output to the bandpass filter 20. The bandpass filter 20 is a filter that passes only 1 MHz, and the signal that has passed through the bandpass filter 20 is sent to the mixer 21.

On the other hand, 1M of the switching signal generator 16
The output of Hz is converted by the frequency converter 22 into a frequency that is smaller by several tens of Hz, and is sent to the mixer 21 via the bandpass filter 23. Therefore, from the mixer 21,
The Hz signal is output. This output is sent to a signal processing circuit (not shown).

There is an on-vehicle radar device of the type in which the signal of the switching signal generator 16 is not sent to the low noise amplifier (LNA) 15. In the case of this device, there is a space between the directional coupler 19 and the mixer 18. Is provided with a frequency converter 24, which converts from 60 GHz to a frequency that is 1 MHz less. Further, in the figure, a portion surrounded by a two-dot chain line 25 shows a millimeter wave circuit.

An embodiment of the input abnormality protection circuit of the present invention provided in the low noise amplifier (LNA) 15 of such an on-vehicle radar device will be described with reference to FIGS. FIG. 3 is a circuit diagram showing a first embodiment of the input abnormality protection circuit. The received signal input from the receiving antenna 14 is sent to the capacitor C1 for cutting the DC component via the terminal 31. The gate of the FET Q1 is connected to the capacitor C1, and the FET Q
The gate-source voltage V _GS1 is applied to the gate of No. 1 through the resistor R1. However, as described later, a control circuit 33 is connected between the V _GS1 voltage terminal 32 and the resistor R1 for detecting the gate current. A capacitor C2 is connected to the resistor R1 and the capacitor C2 is grounded. Resistance R
1 and the capacitor C2 are provided to prevent low frequency oscillation.

The drain of the FET Q1 is connected to the gate of the FET Q2 via the DC component cutting capacitor C4, and the drain-source voltage V _DS1 is applied to the drain of the FET Q1 via the control circuit 33. Further, a series circuit of a resistor R2 and a capacitor C3 for preventing low frequency oscillation is connected to the drain of the FET Q1.

A gate-source voltage V _GS2 is applied to the gate of the FET Q2 via a resistor R3. A capacitor C5 is connected to the resistor R3, and the capacitor C5 is grounded. The resistor R3 and the capacitor C5 are provided to prevent low frequency oscillation. The output from the drain of the FET Q2 is connected to the mixer 18 (FIG. 2) via the DC component cutting capacitor C7, and the drain-source voltage V _DS2 is applied to the drain of the FET Q2.
Further, a series circuit of a resistor R4 and a capacitor C6 for preventing low frequency oscillation is connected to the drain of the FET Q2.

With the above configuration, the FE is applied to the received signal.
High-frequency amplification with low noise is performed by TQ1 and Q2 and output to the mixer 18. By the way, the control circuit 33
_The amount of gate current flowing from the _GS1 voltage supply terminal 32 to the gate of the FET Q1 is detected. When the detected gate current amount is within the predetermined range, the drain-source voltage V _DS1 is applied as it is to the drain of the FET Q1.
However, when the detected gate current amount exceeds a predetermined range and becomes an excessive current amount, that is, when the input is such that the FET Q1 is deteriorated or destroyed, the FET Q
The application of the drain-source voltage V _DS1 to the drain of No. 1 is stopped to eliminate the gain of the FET Q1.
Alternatively, the drain-source voltage applied to the drain of the FET Q1 may be reduced. If it is extremely decreased, it means stopping. By this, FETQ
1 can be protected from deterioration or destruction.

On the other hand, when the detected gate current amount does not reach the predetermined range and becomes an excessively small current amount, that is, because the input signal of a predetermined level or more is not input to the frequency conversion mixer, the millimeter wave circuit When the vehicle-mounted radar device malfunctions and interferes with safe driving, the control circuit 33 sends a signal to the notification device 34 to notify the notification device 34.
Is activated to inform the driver of an abnormality in the on-vehicle radar device. The notification device 34 includes a device that emits an alarm sound, a light emitting device, and the like. The control circuit 33 may control the braking of the vehicle at the time of the above two abnormal inputs (excessive input and excessive input).

FIG. 4 is a circuit diagram showing a second embodiment of the input abnormality protection circuit. In the figure, the same components as those of the first embodiment of FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. Second
In the embodiment, the control circuit 41 does not detect the gate current of the FET Q1, the input signal to the FET Q1 is branched by the directional coupler 42, detected by the wave detector 43, and the detected output is input to the control circuit 41. . The detector 43 has a diode D1.
And resistor R5.

The control circuit 41 applies the drain-source voltage V _DS1 to the drain of the FET Q1 as it is when the detection output input from the detector 43 is within a predetermined range. However, when the detection output exceeds the predetermined range and becomes excessively large, that is, when the input is such that the FET Q1 is deteriorated or destroyed, the drain-source voltage V _DS1 is applied to the drain of the FET Q1. This is stopped and the gain of the FET Q1 is lost. Or FETQ
The drain-source voltage applied to the drain of No. 1 is reduced.

On the other hand, when the detection output does not reach the predetermined range and becomes too small, that is, because the input signal of a predetermined level or more is not input to the mixer for frequency conversion, a malfunction occurs in the millimeter wave circuit. Then, when the on-vehicle radar device malfunctions and interferes with safe driving, the control circuit 41 sends a signal to the notification device 34 to activate the notification device 34, thereby causing the driver to notify of the abnormality of the on-vehicle radar device.

Although the detection output is extracted from the input signal to the FET Q1, it may be extracted from the output signal from the FET Q1 or may be extracted from the input signal or output signal of the FET Q2.

FIG. 5 is a circuit diagram showing a third embodiment of the input abnormality protection circuit. In the figure, the same components as those in the second embodiment of FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted. Third
The embodiment is an input abnormality protection circuit of an on-vehicle radar device of a type in which a switching pulse is applied from the switching circuit 52 (corresponding to the switching signal generator 16 and the switching transistor 17 in FIG. 2) to the drain of the FET Q1. Normally, for example, a switching pulse having an amplitude of 1.5V is applied to the drain of the FET Q1, and the on-vehicle radar device is operating normally.

When the detection output from the detector 43 becomes excessive, the control device 51 activates the switching circuit 52 to reduce the amplitude of the switching pulse, for example, to 0.3V, thereby reducing the gain of the FET Q1. To reduce.

On the other hand, when the detection output becomes too small,
The control circuit 51 sends a signal to the notification device 34 to notify the notification device 3
4 is activated to notify the driver of an abnormality in the on-vehicle radar device.

As in the first embodiment, the control circuit 51 uses the F
The switching circuit 52 may be controlled based on the gate current amount of the ETQ1 (broken line 53). FIG. 6 is a circuit diagram showing a fourth embodiment of the input abnormality protection circuit. In the figure, the same components as those of the first embodiment of FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted.

In the fourth embodiment, the switching circuit 61 (corresponding to the switching signal generator 16 and the switching transistor 17 in FIG. 2) is connected to the drain of the FET Q1, and the drain / source is connected to the drain of the FET Q2 via the control circuit 62. An inter-voltage V _DS2 is applied.

The gate of the FET Q3 is connected to the capacitor C7, and the gate-source voltage V _GS3 is applied to the gate of the FET Q3 via the resistor R6. A capacitor C8 is connected to the resistor R6, and the capacitor C8 is grounded. The resistor R6 and the capacitor C8 are provided to prevent low frequency oscillation.

The output of the drain of the FET Q3 is connected to the mixer 18 via the capacitor C10 for cutting the direct current component, and the drain-source voltage V _DS3 is applied to the drain of the FET Q3. Further, a series circuit of a resistor R7 and a capacitor C9 for preventing low frequency oscillation is connected to the drain of the FET Q3.

The output of the drain of the FET Q3 is branched by the directional coupler 63 and detected by the detector 64, and the detected output is input to the control circuit 62. The detector 64 is composed of a diode D2 and a resistor R8.

This circuit is a circuit when it is not desired to impair the switching function. Therefore, the output of the switching circuit 61 switches the FET Q1 separately from the control circuit 62.

The control circuit 62 applies the drain-source voltage V _DS2 as it is to the drain of the FET Q2 when the detection output input from the detector 64 is within a predetermined range. However, when the detected output exceeds the predetermined range and becomes excessive, the application of the drain-source voltage V _DS2 to the drain of the FET Q2 is stopped to eliminate the gain of the FET Q2. Alternatively, the drain-source voltage applied to the drain of the FET Q2 is reduced. This can prevent the FETs Q2 and Q3 from being deteriorated and destroyed.

On the other hand, when the detection output does not reach the predetermined range and becomes too small, the control circuit 62 sends a signal to the notifying device 34 to operate the notifying device 34, and informs the driver of the abnormality of the on-vehicle radar device. Let me know.

The control circuit 62 may operate based on the gate current amount of the FET Q3 (broken line 65) regardless of the detection output from the detector 64. FIG. 7 is a circuit diagram showing a fifth embodiment of the input abnormality protection circuit. Figure 2
The same components as those of (1) are assigned the same reference numerals and explanations thereof will be omitted.

In the fifth embodiment, when an excessive input is detected, the output on the transmitting side is reduced to protect the low noise amplifier on the receiving side. In the figure, reference numeral 71 is a high output amplifier,
2 is originally connected between the voltage controlled oscillator 12 and the directional coupler 19, but is not shown in FIG.

The control circuit 72 uses the FE as in the first embodiment.
The gate current of T is detected or the detection output is obtained as in the second embodiment to detect the input of the excessive level signal, and at this detection, the operation of the voltage controlled oscillator 12 is stopped.
Alternatively, the drain voltage of the high power amplifier 71 may be reduced.

[0043]

As described above, according to the present invention, the input level of the reflected wave is detected, and the protection means takes measures to protect the in-vehicle radar device at the time of excessive input. Can be protected from deterioration and destruction, and failure of the on-vehicle radar device can be prevented.

Further, when the input is too small, the informing means informs the driver of the abnormality of the on-vehicle radar device, so that the driver can switch to the operation not depending on the on-vehicle radar device.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is a block circuit diagram showing a configuration of an on-vehicle radar device.

FIG. 3 is a circuit diagram showing a first embodiment of an input abnormality protection circuit.

FIG. 4 is a circuit diagram showing a second embodiment of an input abnormality protection circuit.

FIG. 5 is a circuit diagram showing a third embodiment of the input abnormality protection circuit.

FIG. 6 is a circuit diagram showing a fourth embodiment of an input abnormality protection circuit.

FIG. 7 is a circuit diagram showing a fifth embodiment of an input abnormality protection circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 detection means 1a gate current detection means 1b detection voltage detection means 2 abnormal input determination means 3 protection means 3a drain voltage reduction means 3b transmission output reduction means 4 notification means

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masayoshi Ikuno 1-2-2 Goshodori, Hyogo-ku, Kobe, Hyogo Prefecture Inside Fujitsu Ten Limited

Claims (9)

[Claims] 1. A detection means (1) for detecting and outputting a signal level of a reflected wave in an input abnormality protection circuit of an in-vehicle radar device.
An abnormal input discriminating means (2) for discriminating an abnormal input according to the magnitude of the output of the detecting means (1); and an in-vehicle radar device when the abnormal input discriminating means (2) discriminates an excessive input. An input abnormality protection circuit for an on-vehicle radar device, comprising: a protection means (3) for protection. 2. The on-vehicle radar device has a low noise amplifier (LNA) using an FET, and the detecting means (1).
2. The input abnormality protection circuit for a vehicle-mounted radar device according to claim 1, further comprising a gate current detection means (1a) for detecting and outputting a gate current of the FET. 3. The input abnormality protection circuit for an on-vehicle radar device according to claim 1, wherein said detection means (1) comprises detection voltage detection means (1b) for detecting and outputting a detection voltage. 4. The on-vehicle radar device has a low noise amplifier (LNA) using an FET, and the protection means (3).
The input of the vehicle-mounted radar device according to claim 1, characterized in that the abnormal input determining means (2) comprises drain voltage reducing means (3a) for reducing the drain voltage of the FET when the excessive input is determined. Abnormality protection circuit. 5. The low noise amplifier is a switching type low noise amplifier in which a pulse voltage is applied to the drain of the FET, and the drain voltage reducing means (3a) is excessive in the abnormal input discriminating means (2). The input abnormality protection circuit for an on-vehicle radar device according to claim 4, wherein the amplitude value of the pulse voltage applied to the drain of the FET is reduced when the input is determined. 6. The protection means (3) reduces a transmission output reduction means (3) for reducing a transmission side output of the in-vehicle radar device when the abnormal input determination means (2) determines an excessive input.
2. The input abnormality protection circuit for an on-vehicle radar device according to claim 1, wherein the input abnormality protection circuit comprises b). 7. A detection means (1) for detecting and outputting a signal level of a reflected wave in an input abnormality protection circuit of an in-vehicle radar device.
An abnormal input discriminating means (2) for discriminating an abnormal input according to the magnitude of the output of the detecting means (1); and an informing means for informing when the abnormal input discriminating means (2) discriminates an under input. (4) An input abnormality protection circuit for an on-vehicle radar device, comprising: 8. The in-vehicle radar device has a low noise amplifier (LNA) using an FET, and the detecting means (1).
The input abnormality protection circuit for a vehicle-mounted radar device according to claim 7, further comprising a gate current detection means (1a) for detecting and outputting a gate current of the FET. 9. The input abnormality protection circuit for a vehicle-mounted radar device according to claim 7, wherein said detection means (1) comprises detection voltage detection means (1b) for detecting and outputting a detection voltage.