JP2012211855A - Oscillator and onboard radar device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oscillator of which oscillation frequency is stable for temperature variation.SOLUTION: An oscillator 10 oscillating at a predetermined frequency includes an oscillation circuit 11 that has an amplifier and of which oscillation frequency varies according to the operation point of the amplifier and an adjustment circuit 15 that adjusts the operation point of the oscillation circuit according to temperature, thereby adjusting the shift of the oscillation frequency due to the temperature of the oscillation circuit.

Description

  The present invention relates to an oscillation device and an on-vehicle radar device.

  Conventionally, as an oscillating device for oscillating in a high frequency band (for example, a quasi-millimeter wave or a millimeter wave band), for example, a technique shown in Patent Document 1 is known.

Japanese Patent Laid-Open No. 5-110338

  By the way, in the technique disclosed in Patent Document 1, when the environmental temperature changes, the oscillation frequency changes. Such a change in the oscillation frequency due to a change in the environmental temperature has a problem that the stability of the radar characteristics and the detection accuracy are affected when the vehicle-mounted radar device is mounted on a vehicle having a large temperature change.

  Accordingly, an object of the present invention is to provide an oscillation device and an in-vehicle radar device whose oscillation frequency is stable against a temperature change.

In order to solve the above-described problems, the present invention provides an oscillation device that oscillates at a predetermined frequency, having an amplifying element, an oscillation circuit whose oscillation frequency varies depending on an operating point of the amplifying element, and the oscillation according to temperature. And an adjustment circuit that adjusts an oscillation frequency shift due to a temperature of the oscillation circuit by adjusting an operating point of the circuit.
According to such a configuration, it is possible to provide an oscillation device whose oscillation frequency is stable with respect to temperature changes.

According to another aspect of the invention, in addition to the above-described invention, the oscillation circuit includes a transistor as the amplification element, and configures an oscillation circuit by feeding back an output signal of the transistor to an input side terminal of the transistor. The adjustment circuit adjusts an operating point by adjusting a bias voltage of the transistor to adjust an oscillation frequency.
According to such a configuration, it is possible to obtain a high-frequency band oscillation device having high temperature stability.

According to another aspect of the invention, in addition to the above invention, the adjustment circuit includes a thermistor and a resistance element whose resistance value changes with temperature.
According to such a configuration, a change in oscillation frequency due to a temperature change can be efficiently suppressed with a simple circuit configuration.

In addition to the above invention, in another invention, the temperature change is ΔT [° C.], the rate of change of the oscillation frequency due to the temperature change of the oscillation circuit is A [Hz / ° C.], and the operating point by the adjustment circuit When the rate of change of the oscillation frequency of the oscillation circuit based on the change of B is set to B [Hz / V] and the adjustment amount of the operating point by the adjustment circuit is set to ΔVtune, the following equation is established: ΔT = (B / A) Oscillator characterized by xΔVtune.
According to such a configuration, the parameters of the adjustment circuit can be easily obtained.

Another invention is an on-vehicle radar device having the above-described oscillation device.
According to such a configuration, it is possible to provide an on-vehicle radar device that has stable characteristics and high detection accuracy even when mounted on a vehicle having a large temperature change.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the oscillation apparatus and vehicle-mounted radar apparatus whose oscillation frequency is stable with respect to a temperature change.

It is a figure showing an example of composition of an oscillating device concerning a 1st embodiment of the present invention. (A) shows an example of the relationship between the temperature and the oscillation frequency of the first embodiment shown in FIG. 1, and (B) is a diagram showing an example of the relationship between the bias voltage and the oscillation frequency. It is a figure which shows the structural example of the oscillation apparatus which concerns on 2nd Embodiment of this invention. It is a figure which shows an example of the relationship between the temperature and oscillation frequency of 2nd Embodiment shown in FIG. It is a figure which shows an example of the relationship between the bias voltage and oscillation frequency of 2nd Embodiment shown in FIG.

  Next, an embodiment of the present invention will be described.

(A) Description of Configuration of First Embodiment FIG. 1 is a diagram illustrating a configuration example of an oscillation device according to the first embodiment of the present invention. As shown in FIG. 1, the oscillation device 10 includes an oscillation circuit 11, resistance elements 12 and 13, and a thermistor 14.

  Here, the oscillation circuit 11 has an output terminal and a bias terminal, oscillates at a frequency corresponding to a voltage applied to the bias terminal, and outputs an oscillation signal from the output terminal. As an example, the oscillation circuit 11 has a characteristic that the oscillation frequency decreases when the environmental temperature increases, and the oscillation frequency increases when the environmental temperature decreases. The oscillation circuit 11 has a characteristic that the oscillation frequency increases when the bias voltage applied to the bias terminal increases, and the oscillation frequency decreases when the bias voltage decreases. Note that the characteristics of the oscillation frequency depending on the temperature of the oscillation circuit 11 and the characteristics of the oscillation frequency based on the bias voltage may be reverse characteristics of the above characteristics, and do not limit the patentability of this project.

  As an example, the resistance element 13 has one terminal connected to one terminal of the thermistor 14 and the other terminal grounded. The thermistor 14 has one terminal connected to one terminal of the resistance element 13 and the other terminal grounded. The resistance element 12 has one terminal connected to one terminal of the thermistor 14 and the resistance element 13, and the other terminal connected to the power source Vc. The resistance elements 12 and 13 and the thermistor 14 constitute a temperature compensation circuit 15. The thermistor 14 has a PTC (Positive Temperature Coefficient) characteristic in which the resistance value increases as the temperature rises. For this reason, the voltage output from the temperature compensation circuit 15 increases with an increase in temperature. The thermistor 14 may have an NTC (Negative Temperature Coefficient) characteristic in which the resistance value decreases as the temperature rises, depending on the oscillation frequency characteristic due to the temperature of the oscillation circuit 11 and the oscillation frequency characteristic due to the bias voltage. . In addition, the arrangement of the resistance elements is also an example, and does not limit the patentability of this project.

(B) Description of Operation of First Embodiment Next, the operation of the first embodiment will be described. FIG. 2A is a diagram showing the relationship between the fluctuation amount of the oscillation frequency of the oscillation circuit 11 and the change amount of the apparatus temperature. As shown in this figure, the oscillation circuit 11 has a characteristic that the oscillation frequency decreases as the temperature of the device rises. FIG. 2B is a diagram showing the relationship between the voltage applied to the bias terminal of the oscillation circuit 11 and the oscillation frequency. As shown in this figure, in the oscillation circuit 11, when the voltage applied to the bias terminal increases, the oscillation frequency increases, and when the voltage applied to the bias terminal decreases, the oscillation frequency decreases. Further, since the resistance value of the thermistor 14 increases as the temperature rises, the voltage output from the temperature compensation circuit 15 increases as the temperature rises.

Here, each parameter of the oscillation device 10 is set such that the temperature change is ΔT [° C.], the rate of change of the oscillation frequency due to the temperature change of the oscillation circuit 11 shown in FIG. When the voltage applied to the bias terminal of the oscillation circuit 11 shown in 2 (B) and the rate of fluctuation of the oscillation frequency are B [Hz / V], and the amount of change in the voltage applied to the bias terminal is ΔVtune, In the meantime, the following equation (1) holds.
ΔT = (B / A) × ΔVtune (1)

As the temperature compensation circuit 15, the resistance elements 12 and 13 and the thermistor 14 are set so that the following formula (2) is established.
ΔVtune / ΔT = A / B (2)

  For this reason, when the temperature changes by ΔT, the oscillation frequency of the oscillation circuit 11 changes by A × ΔT. The temperature compensation circuit 15 outputs a voltage ΔVtune = A / B × ΔT according to this temperature change. In the oscillation circuit 11, when the bias voltage changes by ΔVtune, the oscillation frequency changes by B × ΔVtune due to the change of the operating point. For this reason, the oscillation frequency of the oscillation circuit 11 changes by A × ΔT. As a result, the change in oscillation frequency A × ΔT due to the change in temperature described above by ΔT is canceled out, so that the oscillation frequency does not change even if the temperature changes.

  As described above, in the first embodiment, the temperature compensation circuit 15 configured by the resistance elements 12 and 13 and the thermistor 14 is added to the oscillation circuit 11 in which the oscillation frequency changes according to the change of the operating point. Since temperature compensation is thereby performed, the oscillation frequency can be prevented from shifting with a simple circuit configuration.

  In the first embodiment described above, since the temperature compensation is performed by hardware using the resistance elements 12 and 13 and the thermistor 14, for example, compared to the case where temperature compensation is performed by software, for example, the center By omitting the control device and the storage device, the configuration of the device can be simplified and the manufacturing cost can be reduced.

(C) Description of Configuration of Second Embodiment Next, the second embodiment will be described. FIG. 3 is a diagram illustrating a configuration example of the second embodiment. As shown in this figure, the oscillation device 20 of the second embodiment has an amplifying element 21, a loop circuit 22, a thermistor 23, resistance elements 24 and 25, and bias circuits 26 and 27.

  Here, the amplifying element 21 is configured by, for example, a high electron mobility transistor (HEMT (High Electron Mobility Transistor)) or a field effect transistor (FET (Field Effect Transistor)). The amplifying element 21 has a source terminal grounded and a drain terminal connected to the power source Vd via the bias circuit 27. The gate terminal is connected to the output terminal of the loop circuit 22, and is connected to one terminal of each of the resistance element 25 and the thermistor 23 via the bias circuit 26.

  The loop circuit 22 has an input end connected to the other end of the bias circuit 27 and an output end connected to the gate terminal of the amplifying element 21. The loop circuit 22 feeds back a signal corresponding to the oscillation frequency among the output signals output via the bias circuit 27 to the gate terminal of the amplifying element 21.

  The thermistor 23 has a PTC type characteristic having a positive temperature characteristic, and its resistance value changes according to a temperature change. One terminal of the thermistor 23 is connected to the gate terminal of the amplifying element 21, and the other terminal is grounded. The resistance element 25 is connected in parallel with the thermistor 23. The resistance element 24 has one terminal connected to the gate terminal of the amplification element 21 via the bias circuit 26 and the other terminal connected to the power supply Vg. The amplifying element 21, the loop circuit 22, and the bias circuits 26 and 27 constitute an oscillation circuit 34, and the thermistor 23 and the resistance elements 24 and 25 constitute a temperature compensation circuit 35.

  The bias circuit 26 is configured by, for example, a microstrip line or a chip component, and one terminal is connected to the gate terminal of the amplification element 21 and the other terminal is connected to one terminal of the resistance element 24. The bias circuit 26 cuts off the direct current component and prevents the function of outputting the oscillation frequency component to the gate terminal of the amplifying element 21 and the signal of the oscillation frequency flowing out from the gate terminal of the amplifying element 21 to the power supply Vg side. A function, and a function of releasing a high-frequency signal from the ground.

  Similar to the bias circuit 26, the bias circuit 27 is configured by a microstrip line or a chip component, and is connected to the drain terminal of the amplifying element 21. The bias circuit 27 cuts off the direct current component and outputs the oscillation frequency component to the circuit and the loop circuit 22 in the subsequent stage (not shown), and the signal of the oscillation frequency that flows out from the drain terminal of the amplifying element 21 to the power supply Vd side. And a function of releasing a high-frequency signal from the ground.

(D) Description of Operation of Second Embodiment Next, the operation of the second embodiment shown in FIG. 3 will be described with reference to FIGS. FIG. 4 is a diagram corresponding to FIG. 2A and shows changes in temperature and oscillation frequency of the second embodiment. FIG. 5 is a diagram corresponding to FIG. B (A) and showing a relationship between the voltage adjustment amount and the variation amount of the oscillation frequency in the second embodiment. This will be specifically described below.

  From FIG. 4, the ratio A [GHz / ° C.] of the change in the oscillation frequency due to the temperature change in the second embodiment is −0.0024. Further, from FIG. 5, the change rate B [GHz / V] of the oscillation frequency due to the change of the bias voltage in the second embodiment is 0.29. Therefore, the temperature compensation circuit 35 sets the element value so that ΔVtune / ΔT = A / B = −0.0082 [V / ° C.].

  By setting in this way, as in the case of the first embodiment, when the oscillation frequency changes due to a temperature change, the bias voltage is adjusted so as to cancel this and the change in the oscillation frequency is canceled out. This will be specifically described below.

  As shown in FIG. 4, when the temperature of the oscillation device 20 changes, as shown in FIG. 4, the oscillation frequency changes according to the change in temperature. For example, when the temperature rises by 20 [° C.], the oscillation frequency decreases by about 0.05 [GHz] (see FIG. 4). Here, as described above, the temperature compensation circuit 35 is set to ΔVtune / ΔT = 0.0082 [V / ° C.]. For this reason, when the temperature rises by 20 [° C.], the voltage ΔVtune increases by about 0.164 [V]. When ΔVtune increases by about 0.164 [V], the voltage (bias voltage) applied to the gate terminal of the amplifying element 21 increases. Then, the operating point of the amplifying element 21 changes and the oscillation frequency changes (rises). Since the increase in frequency is about 0.05 [GHz] as shown in FIG. 5, the oscillation frequency is increased by the amount that cancels the decrease in oscillation frequency due to the temperature increase, and the oscillation frequency does not change.

  As described above, in the second embodiment, when the oscillation frequency of the oscillation device 20 changes due to a temperature change, the operating point is adjusted by changing the bias voltage of the amplification element 21 by the temperature compensation circuit 35. The oscillation frequency was changed so as to cancel the frequency change due to temperature change. Thereby, the temperature compensation of the oscillation device 20 can be performed with a simple circuit configuration.

  In the second embodiment, since the temperature compensation is performed by hardware using the thermistor 23 and the resistance elements 24 and 25, compared with the case where temperature compensation is performed by software, for example, a central processing unit, Since hardware such as a storage device can be eliminated, the circuit configuration can be simplified.

(E) Description of Modified Embodiment The above embodiment is an example, and it is needless to say that the present invention is not limited to the case as described above. For example, in each of the above embodiments, a high electron mobility transistor or a field effect transistor is used as an amplifying element, but an amplifying element other than these (for example, MMIC (Monolithic Microwave Integrated Circuit) or the like) can also be used. It is.

  In the second embodiment described above, the oscillation frequency is adjusted by changing the voltage applied to the gate terminal of the amplifying element 21. For example, the operation can be performed by adjusting the voltage applied to the source terminal. The oscillation frequency may be adjusted by changing the point. In that case, in the circuit shown in FIG. 3, the thermistor 23 and the resistance elements 24 and 25 are excluded from the gate terminal, and the power supply Vg is directly connected to the gate terminal, and is connected in parallel between the source terminal of the amplifying element 21 and the ground. The resistor element 25 and the thermistor 23 may be connected. The element value setting method is the same as that described above.

  Further, in the above embodiment, the configuration of the oscillation device alone is shown. However, the oscillation signal output from these oscillation devices is transmitted as a radio wave, the radio wave reflected from the object is detected, and the transmission signal and the reception signal It is also possible to apply the oscillation device of the present invention to a radar device that detects the position and speed of an object based on a time difference and a frequency difference. In that case, for example, in the case of an on-vehicle radar device, the temperature of the oscillation device may change significantly depending on the environmental temperature, etc., but even in such a case, it can always oscillate at a constant frequency, An object can be detected with high accuracy.

DESCRIPTION OF SYMBOLS 10 Oscillator 11 Oscillator circuit 12, 13 Resistive element 14 Thermistor 15 Temperature compensation circuit 20 Oscillator 21 Amplifying element 22 Loop circuit 23 Thermistor 24, 25 Resistor element 26, 27 Bias circuit

Claims (5)

In an oscillation device that oscillates at a predetermined frequency,
An oscillation circuit having an amplification element, the oscillation frequency of which varies with the operating point of the amplification element;
An adjustment circuit that adjusts the oscillation frequency shift due to the temperature of the oscillation circuit by adjusting the operating point of the oscillation circuit according to the temperature;
An oscillation device comprising: The oscillation circuit includes a transistor as the amplification element, and configures an oscillation circuit by feeding back an output signal of the transistor to an input side terminal of the transistor.
The adjustment circuit adjusts the operating point by adjusting the bias voltage of the transistor, and adjusts the oscillation frequency.
The oscillation device according to claim 1.   The oscillation device according to claim 1, wherein the adjustment circuit includes a thermistor whose resistance value changes with temperature and a resistance element. The temperature change is ΔT [° C.], the rate of change of the oscillation frequency due to the temperature change of the oscillation circuit is A [Hz / ° C.], and the change of the oscillation frequency of the oscillation circuit based on the change of the operating point by the adjustment circuit When the ratio is B [Hz / V] and the adjustment amount of the operating point by the adjustment circuit is ΔVtune, the following equation is established:
ΔT = (B / A) × ΔVtune
The oscillating device according to any one of claims 1 to 3.   An on-vehicle radar device comprising the oscillation device according to claim 1.

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