JPH06216688A - Constant impedance voltage controlled variable attenuator - Google Patents

Abstract

PURPOSE:To eliminate the temperature fluctuation of an attenuation amount by converting a DC voltage to a DC current and making the converted current flow to a PIN diode parallel with high frequencies among the PIN diodes constituted in T type. CONSTITUTION:When the current flowing to a reference resistor 4 increases, a voltage lower than a voltage value outputted at an operational amplifier 7 is applied and the input/output voltages of the operational amplifier 8 are equal. Thus, the potential of the positive side terminal of the operational amplifier 7 falls. Thus, potential difference is generated between the positive/negative terminals of the operational amplifier 7, the output voltage of the operational amplifier 7 is to fall and operates so as not to make the current flow to the reference resistor 4. At this time, the high voltage is applied to the operational amplifier 8 and the output voltage rises as well. Thus, the current flowing to the PIN diode 16 is also fixed regardless of the characteristics of the diode and the temperature fluctuation of the attenuation amount to high frequency signals is eliminated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a constant impedance voltage control variable attenuator having a voltage / current conversion circuit.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing the structure of a conventional constant impedance voltage controlled variable attenuator. In the figure, 1 is an input terminal for receiving a DC voltage, 2 and 5 are resistors, 7 is an operational amplifier, 9 is an input terminal for inputting a microwave signal, 10 is a voltage source of a variable attenuator, 11 is a resistor, and 12 is a coil. 1
3, 14, 15, and 20 are capacitors, 16 is a PIN diode in parallel with a high frequency, 17, 18 is a PIN diode connected in series with respect to a high frequency, and in series in terms of direct current, and 19 is a PIN diode 16. A resistor grounding the PIN diode 18 in a direct current manner, 21 is a terminal for outputting a microwave signal, and 31 and 32 are thermistors.

Next, the operation will be described. When a DC voltage is received at terminal 1 in FIG.
And the resistance value of the thermistor 32, and the thermistors 31 and 3
Inverse amplification and addition are performed according to the ratio of the resistance values of 2,
The voltage corresponding to the DC voltage received by the terminal 1 is output. On the other hand, the microwave signal input from the terminal 9 in the constant impedance variable attenuator passes through the capacitor 13. When the output voltage of the operational amplifier 7 is 0 V, no current flows in the PIN diode 16, so the microwave signal passes through the PIN diodes 17 and 18 in which the current flows and is output from the terminal 21 through the capacitor 20. It
As the output voltage of the operational amplifier 7 increases, a current flows into the PIN diode 16, so that the signal input from the terminal 9 passes through the PIN diode 16 and is grounded through the capacitor 15. In this way, the amount of the microwave signal passing through the PIN diode 16 determines the signal amount output from the terminal 21, and the attenuation amount is determined. The thermistors 31 and 32 change their own resistance values depending on the temperature, change the output voltage of the operational amplifier 7 depending on the temperature, and correct the attenuation amount of the variable attenuator so as not to change with temperature.

[0004]

Since the conventional constant impedance voltage controlled variable attenuator is constructed as described above, the attenuation amount of the constant impedance voltage controlled variable attenuator at all temperatures within the specified temperature range. There was a problem that it was not possible to eliminate the temperature fluctuations. In addition, PI
If the temperature characteristics of the forward current of the N diode are different, the thermistor combination must be changed each time. Further, there is a problem that it is not possible to cope with the secular change in the temperature characteristic of the forward voltage vs. the forward current of the PIN diode.

The present invention has been made in order to solve the above problems, and obtains a constant impedance voltage control variable attenuator in which the attenuation does not fluctuate at all temperatures within a specified temperature range. It is also intended to obtain a constant impedance voltage controlled variable attenuator that does not require circuit modification even if PIN diodes having different temperature characteristics of forward voltage vs. forward current are used. An object of the present invention is to obtain a constant impedance voltage controlled variable attenuator which does not require circuit modification even if the temperature characteristic of the forward voltage vs. forward current of the diode changes over time.

[0006]

A first constant impedance voltage control variable attenuator according to the present invention converts a received DC voltage into a DC current and forms the converted current into a T-shape.
P PIN in parallel with high frequency
It is configured so as to flow to the IN diode. Further, another constant impedance voltage control variable attenuator according to the present invention is one in which a plurality of T-type variable attenuators are arranged, and the first-stage and second-stage PIN diodes are connected in series in a DC manner. The same amount of current is made to flow through the PIN diodes corresponding to the first and second stages.

[0007]

The constant impedance voltage control variable attenuator according to the present invention converts the received direct current voltage into a direct current and converts it into a PIN.
Since the current flows through the diode, the current flowing through the PIN diode is constant with respect to the received DC voltage even if there is a temperature change in the forward voltage vs. the forward current of the PIN diode, and therefore the high frequency characteristics of the PIN diode are also constant.
There is no temperature fluctuation of the attenuation amount of the constant impedance voltage control variable attenuator. For the same reason, even if there is an individual difference in forward voltage vs. forward current of the PIN diode, or there is a secular change in temperature characteristics of forward voltage vs. forward current, a constant impedance voltage control variable attenuator There is no temperature fluctuation of the attenuation amount of.

[0008]

EXAMPLES Example 1. An embodiment of the present invention will be described below with reference to the drawings. 1, 1, 2, 5, 7, 10
21 are the same as the conventional ones. Reference numerals 3 and 6 are resistors, 4 is a reference resistor, and 8 is an operational amplifier for a voltage follower.

Next, the operation will be described. In FIG. 1, the DC voltage received at the terminal 1 is inverted and amplified by the operational amplifier 7, and a voltage is applied to the reference resistor 4. Therefore, the reference resistance 4
An electric current flows through. If the current flowing through the reference resistor 4 increases for some reason, a voltage lower than the voltage value output from the operational amplifier 7 is applied. Since the operational amplifier 8 constitutes a voltage follower, the input and output voltages of the operational amplifier 8 are equal. Therefore, the potential of the + side terminal of the operational amplifier 7 decreases. This causes a potential difference between the +/− terminals of the operational amplifier 7,
The output voltage of the operational amplifier 7 tries to decrease, and the reference resistor 4 works so that no current flows. At this time, a high voltage is applied to the operational amplifier 8 and the output voltage also increases. In this way, when the current flows through the reference resistor 4, it acts so that it does not flow, and when it does not flow, it acts as if it does not flow. Flows. Therefore, the current flowing through the PIN diode 16 is constant regardless of the characteristics of the diode,
The temperature fluctuation of the attenuation amount with respect to the high frequency signal is eliminated. Further, even if there are individual differences in the characteristics of the PIN diode, the amount of attenuation corresponding to the received DC voltage is obtained.

Embodiment 2. Next, another embodiment of the present invention will be described with reference to the drawings. In FIG. 2, 1 to 21 are the same as those in the first embodiment. 28, 29, 30 is 16,
Similar to 17, 18, PIN diodes connected in a T-shape, 25, 26 are capacitors, 24 is a coil in which the first-stage PIN diode 16 and the second-stage PIN diode 28 are DC-connected in series, 27 is a capacitor grounded to the PIN diode 28 and the PIN diode 30, 22 is a voltage power source for the second-stage variable attenuator, and 23 is a resistor.

Next, the operation will be described. In the second embodiment, the parts (9 to 18) of the variable attenuator of the first embodiment are connected in two stages in series. 9 to 21 are the same operations as those in the first embodiment. A current having the same value as that of the PIN diode 16 always flows through the PIN diode 28, which is connected in parallel to the high frequency with the PIN diode 16 in series in terms of direct current. Therefore, the first-stage variable attenuator and the second-stage variable attenuator can always have the same attenuation amount with respect to the microwave signal.

[0012]

Since the present invention is configured as described above, the PIN diode parallel to the high frequency of the constant impedance variable attenuation circuit section has a value corresponding to the received DC voltage regardless of the temperature. Since a current flows, the amount of attenuation with respect to the microwave signal does not change with temperature.
Furthermore, PINs with different temperature characteristics of forward voltage vs. forward current
Even when a diode is used, a constant current corresponding to a DC voltage flows through the PIN diode, so that there is no need to change the design. Further, even if the temperature characteristic of the forward voltage versus the forward current of the PIN diode changes over time, it is not necessary to readjust the circuit.

[Brief description of drawings]

FIG. 1 is a diagram of a constant impedance voltage controlled variable attenuator showing an embodiment of the present invention.

FIG. 2 is a diagram of a constant impedance voltage control variable attenuator showing another embodiment of the present invention.

FIG. 3 is a diagram showing a conventional constant impedance voltage controlled variable attenuator of this type.

[Explanation of symbols]

 1 DC Voltage Input Terminal 2 Resistance 3 Resistance 4 Reference Resistance 5 Resistance 6 Resistance 7 Operational Amplifier 8 Operational Amplifier 9 Microwave Signal Input Terminal 10 Power Supply 11 Resistance 12 Coil 13 Capacitor 14 Capacitor 15 Capacitor 16 PIN Diode 17 PIN Diode 18 PIN Diode 19 Resistor 20 Capacitor 21 Microwave signal output terminal 22 Power supply 23 Resistor 24 Coil 25 Capacitor 26 Capacitor 27 Capacitor 28 PIN diode 29 PIN diode 30 PIN diode 31 Thermistor 32 Thermistor

Claims (2)

[Claims] 1. A high-frequency signal input / output terminal, two PIN diodes provided in series between the input / output terminals, and one PIN diode provided between the two PIN diodes and ground. The operational amplifier provided between this one PIN diode and the control voltage input terminal, another operational amplifier provided between the input and output of this operational amplifier, and the currents of the above three PIN diodes are commonly used. A constant impedance voltage control variable attenuator comprising one flowing resistance, a DC blocking capacitor, and a high frequency blocking coil. 2. A high-frequency signal input / output terminal, and four PIN diodes provided in series between the input / output terminals.
The last two PINs of these four PIN diodes
One PIN between diode and ground
A diode, one PIN diode provided between the first two PIN diodes of the above four PIN diodes in series and between the ground and the one PIN diode
An operational amplifier provided between the diode and the control voltage input terminal, and another provided between the input and output of this operational amplifier.
Constant impedance voltage control variable attenuation characterized by comprising one operational amplifier, one resistor in which the currents of the above six PIN diodes flow in common, a DC blocking capacitor, and a high frequency blocking coil. vessel.