JPH0537530Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Field of Application] This invention relates to a gain adjustment device, and particularly to one in which temperature compensation is performed so that the gain does not fluctuate even if the ambient temperature changes.

[Prior art]

Generally, as the ambient temperature increases, the gain of an amplifier tends to decrease, and as the ambient temperature decreases, the gain tends to increase. This is largely influenced by temperature changes in the amplification transistor. In order to prevent gain fluctuations due to such fluctuations in ambient temperature, conventional
Some amplifiers have a thermistor installed in each bias circuit for the transistors in the amplifier to prevent gain fluctuations due to changes in transistor temperature. Examples are shown in FIGS. 5 and 6. In both figures, 2, 4
is an amplification transistor, and 6 and 8 are bias circuits. Thermistors 10 and 12 are provided on the emitter side of the transistor 2 in the example of FIG. 5, and on the base side of the transistor 4 in the example of FIG. 6, respectively. In both figures, 14 is an RFC, 16 is a DC blocking capacitor, and 18 is a bias capacitor.

[Problem that the invention attempts to solve]

In the devices shown in FIGS. 5 and 6, one thermistor 10, 12 is provided for each transistor 2, 4 constituting the amplifier, and the bias current is used to calculate the gain change due to temperature change of each transistor. The problem was that the cost was high because the prevention was done by changing the In particular, in the case of high-frequency amplifiers, high-frequency amplification stages are often connected in multiple stages, so one thermistor is used for each transistor constituting each amplifier stage.
Providing 0 and 12 requires a great deal of expense and poses a major problem.

[Means for solving problems]

In order to solve the above problems, the present invention has a first PIN diode between the input terminal and the output terminal, and the input terminal of the first PIN diode is connected to the first resistor. A diode series circuit consisting of second and third PIN diodes and a DC blocking capacitor are connected in parallel to the first PIN diode, and a series circuit consisting of a second and third PIN diode is connected to the reference potential point via An attenuation circuit in which the connection point of the PIN diode is connected to the above reference potential point at high frequency, a temperature sensing element whose resistance value decreases as the temperature rises and increases as the temperature decreases, and a variable resistor. A current is supplied from the power supply to the output terminal side of the first PIN diode through the resistor, and a current is supplied from the power supply to the connection point between the diode series circuit and the DC blocking capacitor through the second resistor. and a current adjustment circuit that supplies the current.

[Effect]

According to the present invention, when the ambient temperature is low, the resistance value of the temperature sensing element increases, so the current supplied from the power supply to the first PIN diode via the temperature sensing element and the variable resistor decreases, and the The current supplied to the second and third PIN diodes through the second resistor increases. Therefore, the high frequency resistance value of the first PIN diode increases and the high frequency resistance values of the second and third PIN diodes decrease, so that the high frequency resistance value of the first to third PIN diode increases.
The amount of attenuation of the π-type attenuation circuit composed of PIN diodes increases.

When the ambient temperature is high, the resistance value of the temperature sensing element decreases, so the current supplied from the power supply to the first PIN diode through the temperature sensing element and variable resistor increases, and the current supplied to the first PIN diode through the resistor increases. And the current flowing through the third PIN diode decreases. As a result, the first
The high frequency resistance value of the PIN diode decreases, and the high frequency resistance values of the second and third PIN diodes increase. Therefore, the amount of attenuation of the π-type attenuation circuit composed of the first to third PIN diodes decreases.

Also, when operating the variable resistor, as described above, when the current flowing through the first PIN diode increases, the current flowing through the second and third PIN diodes decreases, and conversely, when the current flowing through the first PIN diode increases, the current flowing through the second and third PIN diodes decreases. When the current flowing in the second and third
The current flowing through the PIN diode increases, and the amount of attenuation is adjusted in the same way as above.

Note that the second and third PIN diodes and the first
Since a DC blocking capacitor is connected between the PIN diode of No current flows through the resistor to the first PIN diode.

〔Example〕

The first embodiment 29 has a PIN diode 30 as shown in FIG. This PIN diode 30
The cathode side of is connected to the cathode side of the PIN diode 32. Also, PIN diode 30
The anode side of is connected via a DC blocking capacitor 36.
It is connected to the anode side of the PIN diode 38. The anode side of the PIN diode 32 and the cathode side of the PIN diode 38 are connected to each other, and their connection point is grounded via a bypass capacitor 40.

The cathode side of the PIN diode 30 is connected to an input terminal 44 via a DC blocking capacitor 42 and grounded via a resistor 46.

The anode side of the PIN diode 30 is connected to an output terminal 50 via a DC blocking capacitor 48. Further, the anode side of the PIN diode 30 is also connected to the arm of the variable resistor 54 via the RFC 52. One end a of this variable resistor 54
is grounded via a semi-fixed resistor 56, and the other end b of the variable resistor 54 is connected to a power supply terminal 60 via a thermistor 58 as a temperature sensing element.
This power supply terminal 60 is connected via a resistor 62 to a connection point between the capacitor 36 and the anode side of the PIN diode 38. resistors 46, 62,
RFC52, variable resistor 54, semi-fixed resistor 56,
The thermistor 58 and the like constitute a current adjustment circuit 64. 66 and 68 are bypass capacitors.

In this embodiment, for example, as shown in FIG. 4, the input terminal 44 is connected to the output side of the final stage of the high frequency amplification stage 70 connected in multiple stages, and the output terminal 50 is connected to the output side of the final stage of the high frequency amplification stage 70 connected in multiple stages. It is connected to the input side of the first stage of 72.

Next, the operation of this Embodiment 29 will be explained. For convenience of explanation, the other end b of the variable resistor 54 is the power supply terminal 60.
This section describes the state in which the device is directly connected to the .
In this state, the arm of the variable resistor 54 is connected to the other end b.
If it is sliding to the side, the PIN diode 30
And the current flowing through the resistor 46 increases. This increases the voltage drop across resistor 46,
The potential on the cathode side of the PIN diode 32 increases, and the current flowing through the PIN diodes 32 and 38 decreases. Therefore, the high frequency resistance value of the PIN diode 30 decreases and the high frequency resistance value of the PIN diodes 32 and 38 increases, so that the signal supplied to the input terminal 44 is sent to the output terminal 50 without being significantly attenuated. .

Further, when one end of the arm of the variable resistor 54 is slid toward the side a, the current flowing through the PIN diode 30 and the resistor 46 is reduced. This causes resistor 46
The voltage drop in the PIN diode 32 becomes smaller, the potential on the cathode side of the PIN diode 32 becomes smaller, and the current flowing through the PIN diodes 32 and 38 increases. Therefore,
The high frequency resistance value of the PIN diode 30 increases,
Since the high frequency resistance values of the PIN diodes 32 and 38 are reduced, the signal supplied to the input terminal 44 is sent to the output terminal 50 after being greatly attenuated.

In this way, when the high frequency resistance value of the PIN diode 30 is large, the high frequency resistance value of the PIN diodes 32 and 38 is small, and conversely, the high frequency resistance value of the PIN diode 30 is small.
When the high frequency resistance value of 0 is small, the high frequency resistance value of the PIN diodes 32 and 38 becomes large, so the amount of attenuation can be changed more than when only the high frequency resistance value of a specific PIN diode is changed. Furthermore, the signal supplied to the input terminal 44 can be attenuated to an amount corresponding to the amount of adjustment of the position of the arm of the variable resistor 54 and sent to the output terminal 50.

Next, the operation of this embodiment 29 will be explained.
Assume now that the arm of the variable resistor 54 is located between one end a and the other end b. In this state, as the ambient temperature increases, the gains of both high frequency amplification stages 70 and 72 become smaller. However, thermistor 58
The resistance value decreases, the current flowing through the PIN diode 30 and the resistance value 46 increases, and the current flowing through the PIN diodes 32 and 38 decreases. In other words, this is equivalent to sliding the arm of the variable resistor 54 toward the other end b side without the thermistor 58, and the amount of attenuation of the signal sent to the output terminal 50 is reduced, resulting in high frequency amplification. The loss in gain at stages 70 and 72 can be compensated for.

Also, when the ambient temperature becomes low, the high frequency amplification stage 7
0.72 gain becomes large. However, the resistance value of the thermistor 58 increases and the PIN diode 3
0, the current flowing through the resistor 46 becomes smaller and the PIN
The current flowing through the diodes 30 and 38 increases. In other words, this is equivalent to sliding the arm of the variable resistor 54 to the other end a side without the thermistor 58, and the amount of attenuation of the signal sent to the output terminal 50 increases, causing high frequency amplification. Steps 70, 72
suppress the increase in gain.

Therefore, in this embodiment 29, even if the ambient temperature rises and falls, the high frequency amplification stage 70 provided with this embodiment 29,
72 total gain can be kept constant.

As shown in FIG. 2, the second embodiment 29a has the same structure as the first embodiment 29, except that the current adjustment circuit 64a has a different structure. Equivalent parts are given the same reference numerals and their explanations will be omitted.

In the first embodiment 29, the thermistor 58 was connected between the other end b of the variable resistor 54 and the power supply terminal 60, whereas in the second embodiment, the variable resistor 58
4 is directly connected to the power supply terminal 60, and a thermistor 58a is connected between the arm of the variable resistor 54 and the RFC 52 instead.

The second embodiment 29a operates similarly to the first embodiment. That is, when the ambient temperature increases, the resistance value of the thermistor 58a decreases, which is equivalent to sliding the arm of the variable resistor 54 toward the other end b, and when the ambient temperature decreases, the resistance value of the thermistor 58a decreases. This is equivalent to sliding one end of the arm of the variable resistor 54 to the side a.

The third embodiment 29b is also configured in the same manner as the first embodiment 29, except that the configuration of the current adjustment circuit 64b is different, as shown in FIG. That is, the variable resistor 54 is removed from the first embodiment 29, and the RFC5
2, a thermistor 58, and a semi-fixed resistor 56 are directly connected. This embodiment 29b also operates in the same manner as the first embodiment 29. Note that this example
29b is suitable when the attenuation amount is not changed frequently.

In each of the above embodiments 29, 29a, and 29b, it is provided between the high frequency amplification stages 70 and 72, but it may be provided on either the input side of the high frequency amplification stage 70 or the output side of the high frequency amplification stage 72.

〔effect〕

As mentioned above, according to the present invention, the first
When the high-frequency resistance value of the PIN diode is large, the high-frequency resistance value of the second and third PIN diodes is reduced, and conversely, when the high-frequency resistance value of the first PIN diode is small, the high-frequency resistance value of the second and third PIN diodes is reduced. Since the circuit is configured to increase the resistance value, the amount of attenuation can vary greatly. Moreover, by operating the variable resistor, the amount of attenuation can be set to any value within the variable range of the amount of attenuation.
The gain adjustment device according to the present invention can be used regardless of the gain that is provided before and after the gain adjustment device, and even if the gain of these amplifiers changes in response to temperature changes, the resistance value of the temperature sensing element remains unchanged. As a result, the high frequency resistance values of the first to third PIN diodes change, and the overall gain of the gain adjustment device according to the present invention and the amplifiers in the front and rear stages can be kept constant regardless of temperature changes. can.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of a first embodiment of this invention, Figure 2 is a circuit diagram of a second embodiment of the same, and Figure 3 is a circuit diagram of a third embodiment of the same.
FIG. 4 is a block diagram of a high frequency amplifier implementing the first to third embodiments.
FIGS. 5 and 6 are block diagrams of a high frequency amplifier equipped with a conventional temperature compensation circuit, respectively. 30, 32, 38...PIN diode, 64,
64a, 64b...Current adjustment circuit, 58, 58a
...Thermistor (temperature sensing element).

Claims (1)

[Claims for Utility Model Registration] A first PIN diode is provided between the input terminal and the output terminal, and the input terminal side of the first PIN diode is connected to a reference potential point via a first resistor. A diode series circuit consisting of second and third PIN diodes and a DC blocking capacitor are connected in parallel to the first PIN diode, and the connection point of the second and third PIN diodes is connected to a high frequency A power source is supplied through an attenuation circuit that is connected to the reference potential point, a temperature sensing element whose resistance value decreases as the temperature rises, and whose resistance value increases as the temperature decreases, and a variable resistor. a current adjustment circuit that supplies current from the power supply to the output terminal side of the first PIN diode and supplies current from the power supply to the connection point between the diode series circuit and the DC blocking capacitor through a second resistor; , a gain adjustment device comprising: