JP3769443B2 - Balanced diode attenuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an attenuator, and more particularly to a balanced attenuator using a diode for attenuating a high frequency signal.
[Prior art]
An attenuator is one of the basic components of an analog electric circuit and is widely used in various circuits. In such an attenuator, it is one of the important elements to minimize the passage loss (hereinafter referred to as dead loss) when the attenuation is minimized and to eliminate the reflection loss even if the attenuation changes. . For this purpose, it is common to configure an attenuator using a PIN diode in a π-type attenuator (attenuation) circuit. However, in such a conventional technique, since the dead loss of the π-type attenuator circuit itself is large, it cannot be said that it is sufficient as an attenuator focusing on the dead loss.
[0003]
Thus, for example, Japanese Patent Application Laid-Open No. 60-256254 discloses a balanced diode attenuator using a 90 ° hybrid. Since this diode is inserted in parallel with the ground (GND), there is no diode package loss, and the dead loss is only 90 ° hybrid, which has a temporary effect in the problem that the dead loss is kept low. .
[0004]
[Problems to be solved by the invention]
However, the above-described conventional balanced diode attenuator is provided with an independent bias circuit for each diode. In this case, since the temperature compensation circuit and the like must be individually configured, there is a problem to be solved that the configuration becomes complicated and expensive.
[0005]
OBJECT OF THE INVENTION
Accordingly, one of the objects of the present invention is to provide a balanced diode attenuator that enables a low dead loss and a common bias circuit. Another object of the present invention is a balanced type in which the frequency characteristics of the diode circuit itself can be adjusted and the 90 ° hybrid on the input side and output side can be separated in a DC manner so that direct current can be superimposed on the input port and output port. It is to provide an attenuator.
[0006]
[Means for Solving the Problems]
The balanced diode attenuator according to the present invention is:
A 90 ° hybrid is connected to each of the input terminal side and output side terminal,
Between the 90 ° hybrid on the input side and the 90 ° hybrid on the output side, first and second diodes having one end grounded are inserted,
A frequency characteristic is set between the first and second diodes and the input side 90 ° hybrid, and first and second capacitors for DC blocking are inserted,
The attenuation is adjusted by applying a bias voltage to the first and second diodes and supplying a common bias current from the 90 ° hybrid isolation port on the output side ,
The input side 90 ° hybrid is inserted with a low-pass filter for superimposing a direct current on the input terminal,
The input side and output side 90 ° hybrid isolation ports are configured to be terminated with a terminating resistor in a high frequency manner through a DC blocking capacitor.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration and operation of a preferred embodiment of a balanced diode attenuator according to the present invention will be described in detail with reference to the accompanying drawings.
[0009]
FIG. 1 is a circuit diagram of a preferred embodiment of a balanced diode attenuator (hereinafter simply referred to as an attenuator) according to the present invention. The attenuator includes an input terminal 1, an output terminal 2, capacitors 3, 4, 7, 8, 10, termination resistors 9 and 11, and a DC superimposing circuit 20. The input terminal 1 is grounded via a capacitor and diodes (PIN diodes) 3-5 and 4-6 connected in series. The anodes of both the diodes 5 and 6 are connected in common and applied with a bias voltage 12 and connected to the output terminal 2 via the capacitor 7 described above, and via the series circuit of the capacitor 8 and the termination resistor 9 described above. Grounded. The input terminal 1 is grounded via the series circuit of the capacitor 10 and the termination resistor 11 described above, and a DC superimposing circuit 20 is further connected. The DC superposition circuit 20 includes a pair of inductors (coils) 21 and 22 connected in series and a capacitor 23 connected between the midpoint of the inductors 21 and 22 and the ground. Is applied.
[0010]
The input side and output side 90 ° hybrids 30a and 30b are connected to the ungrounded ends of the pair of diodes 5 and 6 described above. In other words, the diodes 5 and 6 described above are inserted between the 90 ° hybrid 30a on the input side and the 90 ° hybrid 30b on the output side. Capacitors 3 and 4 inserted between the diodes 5 and 6 and the input-side 90 ° hybrid 30a are selected to have arbitrary values and adjust the frequency characteristics of the attenuator itself. Further, these capacitors 3 and 4 have a direct-current blocking (DC cut) function for the input side and output side 90 ° hybrids 30a and 30b. In this attenuator, a bias voltage is applied to the diodes 5 and 6 from the isolation port of the output side 90 ° hybrid 12. As a result, a bias current is passed through both diodes 5 and 6 by a single common bias circuit, and their dynamic resistance is controlled to make it possible to adjust the attenuation of the attenuator. For this reason, simplification of the temperature compensation circuit and the like can be realized, and variations in the temperature characteristics of the circuit when the temperature compensation circuit is individually provided can be eliminated.
[0011]
Further, as described above, since the input side and output side 90 ° hybrids 30a and 30b are separated from each other by the frequency adjustment capacitors 3 and 4, the input side 90 ° hybrid 30a has the bias voltage 12 described above. A completely different DC voltage 24 can be applied. In the preferred embodiment shown in FIG. 1, the circuit configuration is such that a direct current 24 can be superimposed on the input terminal (port) 1 from the input side isolation port. That is, a low pass filter (LPF) of the DC superimposing circuit 20 is inserted into the isolation port to superimpose a DC current. In addition, input / output terminals 1 and 2 are desired at the isolation ports of the input side and output side 90 ° hybrids 30a and 30b by terminating resistors 11 and 9 in high frequency (RF) via DC blocking capacitors 10 and 8, respectively. Terminate with characteristic impedance (resistance).
[0012]
As is clear from the above description, the balanced diode attenuator according to the present invention has the input side 90 ° hybrid 30a on the input side of the pair of diodes 5 and 6 via the DC blocking and frequency characteristic adjusting capacitors 3 and 4. Connect the 90 ° hybrid 30b to the output side. The input terminal 1 and the output terminal 2 are each terminated with a predetermined impedance, and independent DC voltage 24 and bias voltage 12 can be applied. The bias voltage 12 is applied to both the diodes 5 and 6 in common. The DC voltage 24 to the input terminal 1 side is applied via the DC superposition circuit 20 which is an LPF including the inductors 21 and 22 and the capacitor 23, so that the high frequency signal at the input terminal 1 is effectively leaked or shunted. Can be blocked.
[0013]
It should be understood that the above-described preferred embodiments are merely examples of the present invention and do not limit the present invention. Those skilled in the art will readily understand that various modifications and changes can be made according to a specific application without departing from the technical idea of the present invention.
[0014]
【The invention's effect】
As is clear from the above description, the balanced diode attenuator of the present invention has a relatively simple circuit configuration and can be configured at low cost, and by selecting circuit parameters, the attenuation, frequency characteristics, and It is possible to obtain a remarkable practical effect that various electrical characteristics such as a DC voltage can be arbitrarily selected.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing the configuration of a preferred embodiment of a balanced diode attenuator according to the present invention.
[Explanation of symbols]
1 Input terminal (port)
2 Output terminal (port)
3, 4, 7, 8, 10, 23 Capacitor 5, 6 Diode (PIN diode)
9, 11 Terminating resistor 12 Bias voltage 20 DC superposition circuit 21, 22 Inductor 24 DC voltage 30a Input side 90 ° hybrid 30b Output side 90 ° hybrid

Claims (1)

A 90 ° hybrid is connected to each of the input terminal side and output side terminal,
Between the 90 ° hybrid on the input side and the 90 ° hybrid on the output side, one end is grounded. 1 And a second diode is inserted,
Said 1 And a second diode and a 90 ° hybrid on the input side set frequency characteristics and 1 And a second capacitor inserted,
From the 90 ° hybrid isolation port on the output side, 1 Attenuation is adjusted by applying a bias voltage to the second diode and supplying a common bias current,
The input side 90 ° hybrid is inserted with a low-pass filter for superimposing a direct current on the input terminal,
The balanced diode attenuator is characterized in that the input side and output side 90 ° hybrid isolation ports are terminated with a terminating resistor in a high frequency manner via a DC blocking capacitor.

Images