JP3143902B2 - PIN diode phase shifter - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a PIN diode phase shifter, and more particularly to a reflection type PIN composed of a 90 ° hybrid circuit and a PIN diode.
It relates to a diode phase shifter.

[Conventional technology]

The conventional PIN diode phase shifter has an input terminal 1, an output terminal 2, impedance matching circuits 3 and 4, a phase adjusting circuit 5, and a block diagram showing an example of a conventional PIN diode phase shifter in FIG. 6, PIN diodes 7 and 8, DC blocking capacitors 9 and 10, 90 ° hybrid circuit 11, bias power supply 12, switch circuit 13, and high frequency blocking circuit 15.

The signal input to the input terminal 1 is a DC blocking capacitor 9
Are supplied to the 90 ° hybrid circuit 11 via the
゜ Output as two signals with different phases. This 2
The two signals are applied to PIN diodes 7 and 8 via impedance matching circuits 3 and 4 and phase adjustment circuits 5 and 6, respectively, are reflected respectively, are again passed through a 90 ° hybrid circuit 11, and are output via a DC blocking capacitor 10. Output to terminal 2. When the switch circuit 13 is turned on, a bias current is applied from the bias power supply 12 to the PIN diodes 7 and 8 via the high frequency blocking circuit 15. Therefore, switch circuit 13 is turned ON and OFF.
To turn ON / OFF the bias current applied to PIN diodes 7 and 8.
Then, the impedance of the PIN diode changes according to the bias current, the reflection coefficient changes, and a phase difference occurs in the reflected wave, and a predetermined amount of phase shift can be obtained.

[Problems to be solved by the invention]

The conventional PIN diode phase shifter described above turns on and off the bias current supplied to the PIN diode,
A predetermined amount of phase shift is obtained by changing the reflection coefficient of the N diode.However, the reflection coefficient of the PIN diode when the bias current is ON is different from the reflection coefficient of the PIN diode when the bias current is OFF. Another drawback is that there is a difference in the passage loss between the ON state and the OFF state.

FIG. 3 is a Smith chart showing an example of the reflection coefficient of the PIN diode. Point A represents the impedance of the PIN diode when the bias current is in the ON state, and point B represents the impedance of the PIN diode when the bias current is in the OFF state. Is shown. Since the reflection coefficient indicated by the circle passing through point A is smaller than the reflection coefficient indicated by the circle passing through point B, when the PIN diode is used as a reflection-type phase shifter, the reflection when the bias current is ON is obtained. The loss is larger than the passing loss when the bias current is in the OFF state, and a difference occurs in the passing loss between the ON state and the OFF state.

An object of the present invention is to provide a bias current in an ON state and an OFF state.
An object of the present invention is to provide a PIN diode phase shifter capable of equalizing a passage loss in a state.

[Means for solving the problem]

A PIN diode phase shifter of the present invention is a PIN diode phase shifter that obtains a phase difference by turning a bias current applied to a PIN diode on and off by a switch, and connected to both ends of the switch. OFF
A bias adjustment circuit for supplying a minute bias current to the PIN diode, the bias adjustment circuit having a reflection coefficient of the PIN diode when the bias current is OFF, and a reflection coefficient when the bias current is ON. The minute bias current is adjusted so as to be equal to the absolute value of the reflection coefficient of the PIN diode.

〔Example〕

 Next, the present invention will be described with reference to the drawings.

Referring to FIG. 1 showing an embodiment of the present invention, an input terminal 1, an output terminal 2, impedance matching circuits 3 and 4, phase adjusting circuits 5 and 6, PIN diodes 7 and 8, DC blocking capacitors 9 and 10, It has a 90 ° hybrid circuit 11, a bias power supply 12, a switch circuit 13, a bias adjustment circuit 14, and a high frequency blocking circuit 15.

This figure differs from FIG. 2 showing an example of a conventional PIN diode phase shifter in that a bias adjustment circuit 14 is added. The bias adjustment circuit 14 includes the switch circuit 13
This is for adjusting the bias current supplied from the bias power supply 12 to the PIN diode when is OFF, and its operation will be described with reference to the Smith chart shown in FIG. Point A indicates the impedance of the PIN diode when the switch circuit 13 is ON. Point B indicates the impedance of the PIN diode when the switch circuit 13 is turned off when the bias adjustment circuit 14 is not added. Point B 'indicates the impedance of the PIN diode when the switch circuit 13 is turned off when the bias adjustment circuit 14 is added. That is, the impedance of the PIN diode is shifted from the point B to the point B 'by passing a minute bias current to the PIN diode. In this case, the minute bias current is adjusted so that the absolute value of the reflection coefficient indicated by the radius of the circle passing through the point B 'matches the absolute value of the reflection coefficient indicated by the radius of the circle passing through the point B. By doing so, the PIN
The passage loss of the diode phase shifter can be made equal when the switch circuit 13 is ON and when the switch circuit 13 is OFF.

〔The invention's effect〕

As described above, according to the present invention, when a bias current to be supplied to a PIN diode is in an OFF state, a minute bias current is supplied to the PIN diode when the bias current is in an ON state and when the bias current is in an OFF state. Since the absolute values of the reflection coefficients can be made equal, the passage loss can be made equal.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a block diagram showing an example of a conventional PIN diode phase shifter,
FIG. 3 is a Smith chart showing an example of the reflection coefficient of a PIN diode. 1 ... input terminal, 2 ... output terminal, 3, 4 ... impedance matching circuit, 5, 6 ... phase adjustment circuit, 7, 8 ... PIN diode, 9, 10 ... DC blocking capacitor, 11 ... 90 ゜ Hybrid circuit, 12… Bias power supply, 13… Switch circuit, 14… Bias adjustment circuit, 15… High frequency blocking circuit.

Claims (1)

(57) [Claims] 1. A PIN diode phase shifter which obtains a phase difference by turning on and off a bias current applied to a PIN diode by a switch, wherein the bias current is connected to both ends of the switch, and a small bias current is supplied when the switch is turned off. A bias adjustment circuit that supplies the PIN diode with the reflection coefficient of the PIN diode when the bias current is in an OFF state, and the reflection coefficient of the PIN diode when the bias current is in an ON state. A PIN diode phase shifter, wherein the minute bias current is adjusted so as to be equal to an absolute value of a reflection coefficient.