JP4506719B2 - Variable attenuation circuit for high frequency - Google Patents

Description

  The present invention relates to a high-frequency variable attenuation circuit, and more particularly to a high-frequency variable attenuation circuit that gives a desired attenuation to an input signal in a high frequency band such as a microwave / millimeter wave band.

  As a variable attenuation circuit for a microwave / millimeter wave band, a circuit in which a PIN diode is shunt-connected to a transmission line is generally used. FIG. 5 shows a circuit diagram of an example of this conventional high-frequency variable attenuation circuit. This conventional high-frequency variable attenuation circuit is a variable attenuation circuit when two PIN diodes 28 and 29 are shunt-connected on the transmission line. In FIG. 5, ports 21 and 22 are RF signal input / output ports and ports. Reference numeral 23 denotes a DC voltage application port for controlling the attenuation. Capacitors 24 and 25 are for passing an RF signal from an external circuit and blocking DC voltage from port 23 from leaking to the external circuit.

  Capacitor 26 and coil 27 each connected to port 23 have a low-pass filter configuration in which an applied DC voltage from port 23 is passed and an RF signal is not passed. Elements constituting a circuit for supplying a bias It is. The PIN diode 28 whose anode is connected to the capacitor 24 and whose cathode is grounded, and the PIN diode 29 whose anode is connected to the capacitor 25 and whose cathode is grounded are connected to each other by the DC voltage applied to the port 23. As variable resistance elements whose resistance values change (respective equivalent resistance values are Rv28 and Rv29), they are shunt connected on the transmission line. The length of the transmission line 30 connected between the anodes of the two PIN diodes 28 and 29 is ¼ wavelength.

  In this high-frequency variable attenuation circuit, the resistance values Rv28 and Rv29 of the shunt-connected PIN diodes 28 and 29 are changed by changing the DC bias value applied to the PIN diodes 28 and 29 according to the DC voltage applied to the port 23. Thus, the attenuation amount of the RF signal passing through the transmission line 30 can be changed. That is, when the voltage V23 applied to the terminal 23 is increased in the positive direction, the resistance value Rv28 in the PIN diode 28 decreases and becomes the minimum value Rmin as indicated by I in FIG. The variable attenuation range can be increased by connecting a plurality of shunt-connected PIN diodes having such characteristics. At this time, it is known that when the interval between adjacent PIN diodes 28 and 29 is set to ¼ wavelength of the operating frequency, the effect of linking a plurality is maximized (see, for example, Patent Document 1).

  FIG. 7 is a characteristic diagram of the high-frequency variable attenuation circuit of FIG. The horizontal axis in FIG. 7 represents the DC voltage V23 [V] applied to the port 23, and the vertical axis represents the passing attenuation [dB] of the RF signal between the ports 21-22. The variable attenuation circuit for high frequency shown in FIG. 5 generally exhibits a characteristic that the passage attenuation increases nonlinearly as the DC voltage V23 increases, as indicated by a curve III in FIG.

  As another example of the high-frequency variable attenuation circuit, for example, a variable attenuation circuit shown in a circuit diagram of FIG. 8 is known (see, for example, Patent Document 2). In this variable attenuation circuit, the attenuation circuit 30 connects two PIN diodes 33 and 34 in series and in opposite directions to the signal line between the high-frequency signal input terminal 31 and the high-frequency signal output terminal 32, The anode of the PIN diode 35 whose cathode is grounded is connected to the connection point between the signal input terminal 31 and the cathode of the PIN diode 33, and the cathode is grounded to the connection point between the high-frequency signal output terminal 32 and the cathode of the PIN diode 34. In addition, the anode of the PIN diode 36 is connected, and further, choke coils 37, 38, 39 connected to the bias control circuit 40 are provided.

  In this variable attenuation circuit, when the resistance value of the PIN diodes 35 and 36 is larger than the characteristic impedance value of the signal line by the bias control circuit 40, the current product flowing through the PIN diodes 33 and 35 and the PIN diodes 34 and 36 is constant. When the resistance value of the PIN diodes 35 and 36 is equal to or less than the characteristic impedance value of the signal line, the current flowing through the PIN diodes 34 and 36 is equal to the resistance value of the PIN diodes 35 and 36. And the current flowing through the PIN diodes 33 and 35 is controlled.

  According to this variable attenuation circuit, the amount of attenuation output can be varied by controlling the current flowing through the PIN diodes 33 to 36. Therefore, the number of components required in the attenuation circuit 30 can be reduced, and the shape of the shield case can be reduced. Unnecessary resonance and propagation caused by an increase in the size of the antenna can be suppressed.

Japanese Patent Publication No. 8-15241 (page 3, left column, lines 18 to 23) JP-A-9-214278 (FIG. 1)

  However, in the high-frequency variable attenuation circuit shown in FIG. 5, when the resistance values Rv28 and Rv29 of the PIN diodes 28 and 29 are decreased (the DC voltage applied to the PIN diodes 28 and 29 is increased), the PIN is increased. The quarter wavelength transmission line 30 between the diodes 28 and 29 operates as an antenna, and the feedback amount due to spatial wraparound from the peripheral circuit exceeds the attenuation amount by the PIN diodes 28 and 29, which is indicated by IV in FIG. In some cases, the amount of attenuation increases in the reverse direction.

  When such a reverse increase of the attenuation occurs (an inflection point appears in the attenuation curve), the DC bias voltage for making the attenuation constant cannot be uniquely determined. Accordingly, the attenuation characteristic of the high-frequency variable attenuation circuit is that the attenuation curve does not have an inflection point and needs to be monotonously decreased with respect to the DC bias voltage.

  Conventionally, the following two points have been considered as methods for preventing the reverse increase in attenuation.

  (i) The entire high frequency variable attenuation circuit is covered with a conductor such as metal in order to prevent wraparound to the high frequency variable attenuation circuit.

  (ii) The resistance is connected in series with the PIN diode so that it does not become less than the resistance value (resistance values Rv28 and Rv29 at the voltage value V32 in FIG. 7; resistance value Rj0 in FIG. 6) when the attenuation increases in reverse. Connecting.

  However, when the above measure (i) is adopted, there is a drawback that the three-dimensional structure becomes complicated. On the other hand, the measure (ii) has a simple circuit configuration and is easy to integrate. However, the resistance value Rj0 at which an inflection point appears in the attenuation curve changes due to variations in the resistance value of the PIN diode itself, variations due to assembly such as the wire length, variations in load impedance of elements connected to the variable attenuation circuit, and the like. Therefore, it is necessary to connect a compensation resistor capable of individually dealing with these variations in series to the attenuating PIN diode.

  Further, in the conventional high-frequency variable attenuation circuit shown in FIG. 8, the metal shield case covering the entire high-frequency variable attenuation circuit corresponding to the measure (i) can be reduced in size, but the PIN diode 33, When the voltage applied to 34 is changed, the voltage applied to the PIN diodes 35 and 36 also changes. Therefore, in order to use the PIN diodes 33 and 34 as variable resistance elements for compensation, a bias control circuit for the attenuation circuit 30 is used. The bias control by 40 becomes complicated, and the circuit configuration becomes extremely complicated.

  The present invention has been made in view of the above points, and provides a high-frequency variable attenuation circuit that can cope with variations in circuit elements and changes in peripheral circuits with a simple configuration and that can minimize deterioration of the variable attenuation range. Objective.

  In order to achieve the above object, according to the present invention, a first input / output port is connected to a second input / output port via a transmission line, and the first input / output port and one end of the transmission line are connected. The bias voltages of the first attenuating PIN diode connected to the connection point of the second attenuating PIN diode and the second attenuating PIN diode connected to the connection point of the other end of the transmission line and the second input / output port are changed. As a result, a desired attenuation amount is given to an input signal in the microwave / millimeter wave band that is input to one of the first and second input / output ports and output from the other, and the attenuation amount is In the high-frequency variable attenuation circuit having a variable attenuation characteristic, the first resistance value of the first attenuation PIN diode and the first attenuation PIN at the inflection point where the attenuation amount reversely increases in the attenuation characteristic. Difference from the minimum resistance of the diode A first variable resistance element connected in series to a first attenuating PIN diode, the resistance value of which is variable and adjustable, and an inflection point at which the attenuation increases in reverse. Is set to a predetermined resistance value corresponding to the difference between the second resistance value of the second attenuating PIN diode and the minimum resistance value of the second attenuating PIN diode, and the resistance value is variably adjustable. And a second variable resistance element connected in series to the second attenuating PIN diode.

  In the present invention, the first and second attenuation when the resistance values of the first and second variable resistance elements connected in series to the first and second attenuation PIN diodes appear as inflection points in the attenuation characteristic. Since the resistance value (Rc) of the difference between the first and second resistance values (Rj0) of the PIN diode for use and the minimum resistance value (Rmin) of the first and second attenuation PIN diodes is set, With a simple configuration including the first and second variable resistance elements, it is possible to prevent an inflection point at which the attenuation amount reversely increases in the attenuation characteristic.

  Here, the first variable resistance element is a first compensation PIN diode connected in series in the reverse direction with respect to the first attenuation PIN diode, and the second variable resistance element is a second attenuation resistance element. The second compensation PIN diode is connected in series in the opposite direction to the PIN diode for use.

  In the present invention, the first and second compensation PIN diodes described above are the first and second compensation PIN diodes when the common DC voltage is applied as the bias voltage and the inflection point in the attenuation characteristic reversely increases. And a predetermined resistance value corresponding to a difference between the resistance value of the second attenuation PIN diode and the minimum resistance value of the first and second attenuation PIN diodes. Thereby, the circuit configuration can be further simplified.

  Further, the present invention provides the first and second DC voltages applied as a bias voltage in common to the first and second compensation PIN diodes at the inflection points at which the attenuation amount reversely increases in the attenuation characteristic. According to another aspect of the present invention, the adjustment is variably performed according to a predetermined resistance value corresponding to a difference between the resistance value of the second attenuation PIN diode and the minimum resistance value of the first and second attenuation PIN diodes. In the present invention, even if the first and second resistance values (Rj0) change due to variations in circuit elements and changes in peripheral circuits, the resistance values of the first and second variable resistance elements are correspondingly changed. Can be variably set.

  In order to achieve the above object, the first input / output port is connected to the second input / output port via the transmission line, and the first input / output port and the transmission line are connected to each other. Each bias voltage of the first attenuating PIN diode connected to the connection point with one end and the second attenuating PIN diode connected to the connection point between the other end of the transmission line and the second input / output port Is applied to one of the first and second input / output ports, and a desired attenuation is given to the input signal of the microwave / millimeter wave band output from the other, and the attenuation is applied. In a high-frequency variable attenuation circuit having a variable attenuation characteristic, a first compensation PIN diode and a second attenuation PIN diode connected in series in the opposite direction to the first attenuation PIN diode Opposite to A variable attenuating DC voltage for obtaining a desired attenuation amount is used as a bias voltage at a connection point between the second compensating PIN diode connected in series, the first attenuating PIN diode, and one end of the transmission line. A predetermined compensation DC voltage having an absolute value smaller than that of the attenuation DC voltage and having a different polarity is applied to the attenuating DC voltage application means, the first compensation PIN diode, and the second compensation PIN diode. A compensation DC voltage application means for commonly applying a voltage as a bias voltage. The compensation DC voltage application means attenuates each resistance value of the first compensation PIN diode and the second compensation PIN diode. The resistance values of the first attenuation PIN diode and the second attenuation PIN diode, the first attenuation PIN diode, and the first attenuation diode at the inflection point where the attenuation amount rises in the reverse direction. A compensation DC voltage for setting a resistance value corresponding to a difference from the minimum resistance value of the attenuating PIN diode is generated, and a common connection between the first attenuating PIN diode and the first compensating PIN diode is generated. And a common connection point of the second attenuating PIN diode and the second compensating PIN diode, respectively.

  In the present invention, the resistance values of the first and second compensation PIN diodes connected in series to the first and second attenuating PIN diodes are the first and second when the resistance values appear as inflection points in the attenuation characteristics. The resistance value (Rc) is set to the difference between the first and second resistance values (Rj0) of the attenuation PIN diode and the minimum resistance value (Rmin) of the first and second attenuation PIN diodes. With a simple configuration including the first and second compensation PIN diodes, it is possible to prevent an inflection point at which the attenuation amount reversely increases in the attenuation characteristic.

  In order to achieve the above object, the present invention provides a common connection point between the first attenuation PIN diode and the first compensation PIN diode and the second attenuation DC diode by the compensation DC voltage application means. After applying the compensation DC voltage to the common connection point of the PIN diode and the second compensation PIN diode, the connection between the first attenuation PIN diode and one end of the transmission line is performed by the above-described attenuation DC voltage application means. A DC voltage for attenuation is applied as a bias voltage to the point.

  According to the present invention, the resistance value of the first and second compensation PIN diodes (first and second variable resistance elements) connected in series to the first and second attenuation PIN diodes is expressed in the attenuation characteristic. The first and second resistance values (Rj0) of the first and second attenuation PIN diodes when appearing as inflection points, and the minimum resistance value (Rmin) of the first and second attenuation PIN diodes By setting the resistance value (Rc) as a difference, an inflection point where the attenuation amount increases in the attenuation characteristic is prevented from appearing. Therefore, the first and second compensation PIN diodes (the first and second variable PIN diodes). In addition to providing a resistance element, a very simple configuration that simply provides a means for fixedly setting it to the resistance value (Rc) described above causes deterioration of the attenuation characteristic due to spatial wraparound (the attenuation characteristic curve is an inflection point) With a variable attenuation range The can be minimized.

  Further, according to the present invention, even if the first and second resistance values (Rj0) change due to variations in circuit elements and changes in peripheral circuits, the first and second compensation PINs are correspondingly changed. Since the resistance value of the diode (variable resistance element) can be variably set, it is possible to individually cope with the above-described variations in circuit elements and changes in peripheral circuits, and to adjust the deterioration of the variable attenuation range to the minimum. .

  Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit diagram of an embodiment of a variable attenuation circuit for high frequency according to the present invention. In FIG. 1, ports 1 and 2 are RF signal input / output ports, port 3 is a DC voltage application port for controlling the attenuation, and port 11 is a compensation DC voltage application port. Capacitors 4 and 5 are for passing an RF signal from the external circuit and blocking leakage of the DC voltage from port 3 to the external circuit.

  Capacitor 6 and coil 7 having one end connected to port 3 have a low-pass filter configuration in which an applied DC voltage from port 3 is passed and an RF signal is not passed. Elements constituting a circuit for supplying a bias It is. Similarly, the capacitor 12 and the coil 13 each having one end connected to the port 11 have a low-pass filter configuration in which the applied DC voltage from the port 11 is passed and the RF signal is not passed. It is the element which comprises.

  The connection point between the capacitor 4 and the coil 7 is connected to the anode of the high frequency attenuation PIN diode 8, and the connection side terminal of the capacitor 5 is connected to the anode of the high frequency attenuation PIN diode 9. Yes. The cathodes of the PIN diodes 8 and 9 are connected in common to the cathodes of the compensation PIN diodes 14 and 15 whose anodes are grounded. The terminal on the opposite side to the connection terminal of the port 11 of the coil 13 is connected to the common connection point of the PIN diodes 8, 9, 14 and 15. Further, the transmission line 10 is connected between the anodes of the two PIN diodes 28 and 29, and the length thereof is ¼ wavelength. The equivalent resistance values of the PIN diodes 8, 9, 14, and 15 which are variable resistance elements whose resistance values change depending on the DC voltage are Rv8, Rv9, Rv14, and Rv15, respectively.

  In this embodiment, a port 11, a capacitor 12, a coil 13, and PIN diodes 14 and 15 are provided, and PIN diodes 14 and 15 are used as variable resistance elements for compensation to prevent the attenuation curve from having an inflection point. There is a feature. The PIN diodes 14 and 15 are compensation variable resistance elements, and as shown in FIG. 1, the anode and cathode are connected in series in the opposite direction to the attenuation PIN diodes 8 and 9, respectively. The capacitor 12 and the coil 13 have a low-pass filter configuration in which an applied voltage from the port 11 is allowed to pass and an RF signal is not passed, and are elements constituting a circuit for supplying a bias.

  Next, the operation of the present embodiment will be described with reference to FIGS. In general, an equivalent circuit of a PIN diode in a high frequency band is shown in FIG. 2A. When a DC voltage V is applied to the diode in the forward direction, a nonlinear junction is formed as shown in FIG. A parallel circuit of a resistor Rj and a non-linear junction capacitor Cj is represented by a circuit connected in series to the resistor Rs. The relationship between the combined resistance Rv of the resistors Rs and Rj and the DC voltage V that is a forward bias voltage to the diode is as shown in FIG.

  As is well known, a PIN diode has a junction structure in which an intrinsic semiconductor region (that is, an I layer) is sandwiched between a P layer and an N layer, and carriers cannot follow an RF signal by the I layer. It can be considered that the resistance value Rv is determined only by the bias DC voltage V applied to.

  Consider the case where a variable attenuation circuit as shown in FIG. 5 is configured using a PIN diode having such characteristics (conventional circuit configuration). By applying a voltage to the port 23 in FIG. 5, the resistance values Rv28 and Rv29 of the attenuating PIN diodes 28 and 29 are lowered as shown in FIG. 6, resulting in an RF between the ports 21-22. The signal passing attenuation increases. However, when the resistance values Rv28 and RV29 of the attenuating PIN diodes 28 and 29 are less than a certain value (hereinafter referred to as Rj0), the amount of attenuation increases reversely (the attenuation curve has an inflection point as shown by the characteristic II in FIG. May have).

  This means that an inflection point does not appear in the attenuation curve unless the resistance value of the portion connected to the transmission line is shunt Rj0 or less. Therefore, the resistance value Rc between the resistance value Rj0 appearing at the inflection point in the attenuation curve shown in FIG. 6 and the minimum resistance value Rmin of the PIN diode is connected in series to the attenuation PIN diode as a compensation resistor. That's fine. However, since the resistance value Rj0 at which the inflection point appears in the attenuation curve varies depending on the change in the circuit configuration or the like, in this embodiment, the PIN diodes 14 and 15 that are variable resistance elements are used as the compensation resistors.

  That is, in the present embodiment, as shown in FIG. 1, a circuit configuration in which the compensation PIN diodes 14 and 15 are connected in series to the attenuation PIN diodes 8 and 9 so that the directions of the anode and the cathode are opposite to each other. And As a result, the variable attenuation range of the variable attenuation circuit according to the present embodiment is obtained by adding the resistance values Rv14 and Rv15 of the compensation PIN diodes 14 and 15 to the minimum value of the resistance values Rv8 and RV9 of the attenuation PIN diodes 8 and 9. It is determined by the resistance value.

  Here, the relationship between the voltage V11 applied to the port 11 in FIG. 1 and the resistance value Rv14 of the compensation PIN diode 14 is shown in FIG. In the present embodiment, in the voltage-resistance value characteristic of the PIN diode in FIG. 3, the applied voltage V11c at which the resistance value Rv14 becomes the resistance value Rc is fixedly applied. The resistance value Rc is a difference resistance value between the resistance value Rj0 appearing at the inflection point in the attenuation curve shown in FIG. 6 and the minimum resistance value Rmin of the PIN diode.

  In the present embodiment, as shown in FIG. 1, the compensation PIN diodes 14 and 15 are connected in series to the attenuating PIN diodes 8 and 9 so that the anode / cathode directions are opposite to each other. Therefore, first, by applying a negative fixed voltage V11c (which corresponds to V11c in FIG. 3) to the port 11, a forward bias voltage is applied only to the PIN diodes 14 and 15, and the PIN diodes 14 and 15 are applied. Only the resistance values Rv14 and Rv15 are fixed to the resistance value Rc. Thereafter, a positive voltage having a larger absolute value than V11c is applied to port 3, and the voltage applied to port 3 is varied to vary the forward bias voltage only for PIN diodes 8 and 9, and PIN. The resistance values Rv8 and Rv9 of the diodes 8 and 9 can be varied to obtain a desired attenuation.

  Thus, in this embodiment, since the resistance value Rc is added for compensation to the minimum value Rmin of the resistance values Rv8 and Rv9, the variable resistance control DC voltage applied to the attenuation PIN diodes 8 and 9 is used. Within the value range, it is possible to minimize the deterioration of the variable attenuation range and monotonously decrease the attenuation characteristic similar to the characteristic indicated by II in FIG. Thereby, the attenuation characteristic of the high-frequency variable attenuation circuit of FIG. 1 is as shown in FIG.

  4, the horizontal axis represents the DC voltage V3 [V] applied to the port 3 in FIG. 1, and the vertical axis represents the RF signal passing attenuation [dB] between the ports 1-2. As shown in FIG. 4, in the attenuation characteristic V of the present embodiment, the reverse increase of the attenuation amount is not seen as in the characteristic IV in FIG. 7 of the conventional circuit. On the other hand, it is monotonically decreasing.

  The resistance value at which the inflection point appears in the attenuation curve changes depending on variations in circuit elements and changes in peripheral circuits, but in this embodiment, the resistance values of the compensation PIN diodes 14 and 15 are changed (application to the port 11). By changing the DC voltage), it is possible to individually cope with this change and adjust the deterioration of the variable attenuation range to the minimum.

  As described above, according to the present embodiment, the port 11, the capacitor 12, the coil 13, and the PIN diodes 14 and 15 are provided with a very simple configuration as compared with the conventional variable attenuation circuit described in Patent Document 2, It is possible to cope with variations in circuit elements and changes in peripheral circuits, and to minimize deterioration of the variable attenuation range.

1 is a circuit diagram of an embodiment of a variable attenuation circuit for high frequency according to the present invention. FIG. It is a figure which shows the equivalent circuit and applied voltage versus resistance characteristic of a PIN diode. It is a figure which shows the relationship between the voltage applied to the port 11 in FIG. 1, and the resistance value of the compensation PIN diode 14. FIG. FIG. 2 is an attenuation characteristic diagram of the high-frequency variable attenuation circuit in FIG. 1. It is a circuit diagram of an example of the conventional variable attenuation circuit for high frequencies. 6 is a diagram illustrating a relationship between a DC voltage applied to a port 23 of the high-frequency variable attenuation circuit in FIG. 5 and a resistance value of a PIN diode 28. FIG. FIG. 6 is an attenuation characteristic diagram of the high-frequency variable attenuation circuit in FIG. 5. 10 is a circuit diagram of an example of a conventional high-frequency attenuation circuit described in Patent Document 2. FIG.

Explanation of symbols

1, 2 RF signal input / output port 3 Attenuation control DC voltage input port 4, 5 DC blocking capacitor 6, 12 Low pass filter capacitor 7, 13 Low pass filter coil 8, 9 High frequency attenuation PIN diode 10 Transmission line 11 DC voltage input port for compensation 14, 15 PIN diode for compensation

Claims (6)

A first input / output port is connected to the second input / output port via a transmission line, and is connected to a connection point between the first input / output port and one end of the transmission line. By changing each bias voltage of the second attenuating PIN diode and the second attenuating PIN diode connected to the connection point between the other end of the transmission line and the second input / output port, the first attenuating PIN diode is changed. In addition, a desired attenuation amount is given to an input signal in the microwave / millimeter wave band that is input to one of the second input / output ports and output from the other, and an attenuation characteristic that can change the attenuation amount is provided. In the high-frequency variable attenuation circuit provided,
A resistance corresponding to a difference between a first resistance value of the first attenuating PIN diode and a minimum resistance value of the first attenuating PIN diode at the inflection point where the attenuation amount increases in the attenuation characteristic in the reverse direction. A first variable resistance element connected in series to the first attenuating PIN diode, the resistance value of which is set to be variable and the resistance value of which can be variably adjusted;
A predetermined resistance value corresponding to the difference between the second resistance value of the second attenuating PIN diode and the minimum resistance value of the second attenuating PIN diode at the inflection point at which the attenuation amount rises backward And a second variable resistance element connected in series to the second attenuation PIN diode, the resistance value of which can be variably adjusted.   The first variable resistance element is a first compensation PIN diode connected in series in the opposite direction to the first attenuation PIN diode, and the second variable resistance element is the second attenuation resistance diode. 2. The high-frequency variable attenuation circuit according to claim 1, wherein the high-frequency variable attenuation circuit is a second compensation PIN diode connected in series in the opposite direction to the PIN diode.   In the first and second compensation PIN diodes, a common DC voltage is applied as a bias voltage, and the first and second attenuation PIN diodes at the inflection point where the attenuation amount reversely increases in the attenuation characteristic. 3. The variable attenuation for high frequency according to claim 2, wherein a predetermined resistance value corresponding to a difference between a resistance value of a PIN diode and a minimum resistance value of the first and second attenuation PIN diodes is set. circuit.   The DC voltage applied as a bias voltage in common to the first and second compensation PIN diodes is the first and second attenuation PINs at the inflection point where the attenuation amount reversely increases in the attenuation characteristic. 4. The high frequency device according to claim 3, wherein the resistance value is variably adjusted according to a predetermined resistance value corresponding to a difference between a resistance value of the diode and a minimum resistance value of the first and second attenuation PIN diodes. Variable attenuation circuit. A first input / output port is connected to the second input / output port via a transmission line, and is connected to a connection point between the first input / output port and one end of the transmission line. By changing each bias voltage of the second attenuating PIN diode and the second attenuating PIN diode connected to the connection point between the other end of the transmission line and the second input / output port, the first attenuating PIN diode is changed. In addition, a desired attenuation amount is given to an input signal in the microwave / millimeter wave band that is input to one of the second input / output ports and output from the other, and an attenuation characteristic that can change the attenuation amount is provided. In the high-frequency variable attenuation circuit provided,
A first compensation PIN diode connected in series in a reverse direction with respect to the first attenuating PIN diode;
A second compensation PIN diode connected in series in the opposite direction to the second attenuating PIN diode;
Attenuating DC voltage applying means for applying, as a bias voltage, a variable attenuating DC voltage for obtaining the desired attenuation amount to a connection point between the first attenuating PIN diode and one end of the transmission line;
The first compensation PIN diode and the second compensation PIN diode share a predetermined compensation DC voltage having a smaller absolute value than the attenuation DC voltage and having a different polarity as a bias voltage. Compensation DC voltage application means for applying, wherein the compensation DC voltage application means attenuates each resistance value of the first compensation PIN diode and the second compensation PIN diode in the attenuation characteristic. The resistance values of the first attenuation PIN diode and the second attenuation PIN diode and the first attenuation PIN diode and the second attenuation PIN diode at the inflection point where the amount increases in reverse. A compensation DC voltage for setting a resistance value corresponding to a difference from the minimum resistance value is generated, and the first attenuation PIN diode and the first compensation P voltage are generated. A high-frequency variable attenuation circuit comprising: a common connection point of an IN diode; and a common connection point of the second attenuation PIN diode and the second compensation PIN diode. By the compensation DC voltage application means, a common connection point of the first attenuation PIN diode and the first compensation PIN diode, and the second attenuation PIN diode and the second compensation PIN diode After applying the compensation DC voltage to each common connection point, the attenuation DC voltage application means biases the attenuation DC voltage to a connection point between the first attenuation PIN diode and one end of the transmission line. 6. The variable attenuation circuit for high frequency according to claim 5, wherein the variable attenuation circuit is applied as a voltage.

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