JPH0447801A - Variable phase device - Google Patents

Abstract

PURPOSE:To keep almost constant a return loss when varying a phase by connecting a resistor having a prescribed resistance value parallelly to a variable capacity diode. CONSTITUTION:High frequency power inputted from an input terminal 1 is inputted through a capacitor 4 to a variable capacity diode 7. A negative voltage impressed from a direct current impressing terminal 3 is impressed through a high impedance line 5 to the anode of the diode 7. The high frequency power to be inputted to the diode 7 is outputted from the terminal 1 after being reflected at a reflecting phase corresponding to the capacity of the diode 7 to be changed by this impressed voltage. A resistor 6 and a capacitor 8 for high frequency ground are connected parallelly to the diode 7. When this resistor 6 (a resistance value R expressed by a formula I) is connected, the change in the reflection coefficient of the diode 7 can be kept almost constant.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable phase shifter, which is particularly used for high frequencies;
This invention relates to a variable phase shifter that changes the phase of a high frequency signal using a voltage controlled variable capacitance diode.

[Conventional technology]

Conventionally, this type of variable phase shifter, as shown in the circuit diagram of FIG. capacitor 14,
Variable capacitance diode 17, this variable capacitance diode 17
It is comprised of a DC voltage application terminal 13 for supplying a DC voltage via a high impedance circuit 15 for high frequencies.

The operation of the conventional example shown in FIG.
The capacitance of the variable capacitance diode 17 is controlled by applying and varying the voltage, and the reflection impedance of the diode is changed to change the reflection phase of the high frequency. Furthermore, in order to make the high frequency power input terminal 11 and the output terminal 12 independent when used as a variable phase shifter, a circulator 16 or a hybrid is used. Here, the characteristic of the amount of return loss from the diode with respect to the capacitance change Cv of the variable capacitance diode is that the amount of return loss changes significantly as shown in the conventional characteristic shown in the characteristic diagram of FIG. 5(a).

[Problems to be Solved by the Invention] The conventional variable phase shifter described above has a high frequency power input from a high frequency input terminal that is input to a variable capacitance diode, and the DC mark is reversed by the change in capacitance of the diode according to the voltage. This has the disadvantage that the output level of the phase shifter fluctuates and the loss also increases because the phase shifter changes significantly.

[Means to solve the problem]

The variable phase shifter of the present invention includes a variable capacitance diode, a DC voltage terminal to which a DC voltage is applied to change the capacitance of the variable capacitance diode, and a high frequency power input to the variable capacitance diode to change the DC voltage. In the variable phase shifter, the resistance value RA of the resistor connected in parallel with the variable capacitance diode has a characteristic impedance of the variable phase shifter main body as Zo, and If the equivalent series resistance of the capacitive diode is R, then the resistance value is as follows.

〔Example〕

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

FIG. 1(a) is a circuit diagram of an embodiment of the present invention, and FIG. 1(b) is a circuit diagram of an embodiment of the present invention.
) is an equivalent circuit diagram of a variable capacitance diode. High frequency power input from the high frequency input terminal 1 is input to the variable capacitance diode 7 via the capacitor 4 for cutting off DC current. A negative voltage applied from the DC application terminal 3 is applied to the anode of the variable capacitance diode 7 via a high impedance line 5 which is a high frequency choke.

The high frequency power input to the variable capacitance diode 7 is reflected at a reflection phase according to the capacitance of the diode 7, which changes with this applied voltage, and is output from the high frequency input terminal 1. Further, a resistor 6 and a high-frequency grounding capacitor 8 are connected in parallel with the variable capacitance diode 7, and the resistance value RA of the resistor 6 is determined by setting the equivalent series resistance of the diode 7 to R, and the characteristic impedance of this phase shifter to Z. . Then, the value is selected to be the value expressed by the equation (3>).

Now, if this resistor 6 (resistance value RA) is connected,
The change in the reflection coefficient of the variable capacitance diode 7 can be kept almost constant compared to the case where it is not connected. This state will be explained by comparing the impedance chart of the present embodiment shown in FIG. 5, ie, the case where the resistor 6 is connected, and the impedance chart of the conventional example shown in FIG. 4, ie, the case where the resistor 6 is not connected. Variable capacitance diode 7 has a reflection coefficient of 1 "A1" at the point A where the capacitance is minimum and a reflection coefficient 1 "B" of the point B where the capacitance is maximum.The change in 1 moves on the equireactance circle on the impedance chart in Figure 3, so the capacitance changes. The reflection coefficient, that is, the return loss, changes accordingly.In other words, when the capacitance of the reflection impedance looking into the variable capacitance diode is changed, the locus will be the reflection coefficient 1r'AI at the point A with the minimum capacitance and the point A with the maximum capacitance. The reflection coefficient IT''it of B is different. By adding the resistor RA here, the impedance A' can be moved to the point A where the capacitance is minimum as shown in FIG. 4, and the reflection coefficient can be kept at a substantially constant value when the phase is varied. Figures 5(a) and 5(a) compare calculation examples of return loss and reflection phase using the capacitance change Cv of the variable capacitance diode of a variable phase shifter that performs such an operation as a parameter and compare it with a conventional example.
As shown in the characteristic diagram b), and as an application example of such a variable phase shifter, as shown in FIG. The high frequency signals input from the variable capacitance diode 7A and the variable capacitor 7B are phase-shifted and combined into the same phase without any loss deviation, and can be output from the output terminal 2.

〔Effect of the invention〕

As explained above, the present invention has the effect of keeping the return loss substantially constant when changing the phase by connecting a resistor having a resistance value RA in parallel to the variable capacitance diode.

By incorporating two such variable phase shifters into a 3 dB hybrid, it is possible to realize a variable phase shifter with less loss deviation during phase shifting.

[Brief explanation of drawings]

1 and 2 are circuit diagrams of one embodiment of the present invention, and FIG.
Figure 4 is an explanatory diagram comparing this embodiment with the conventional example, and Figure 5 is an explanatory diagram comparing this embodiment with the conventional example.
Figures (a) and (b) are characteristic diagrams of this embodiment and a conventional example, and Fig. 6 is a circuit diagram of a conventional variable phase shifter. 1... High frequency input terminal, 2... (high frequency) output terminal, 3... DC application terminal, 4, 4A, 4B, 8.8A. 8B...Capacitor, 5.5A, 5B...High impedance line, 6.6A, 6B...Resistor, 7,7A. 7B... Variable capacitance diode, 9... Hybrid circuit.

Claims (2)

[Claims] 1. A variable capacitance diode, a DC voltage terminal to which a DC voltage is applied to change the capacitance of the variable capacitance diode, and a high frequency power input to the variable capacitance diode to output high frequency reflected power in accordance with changes in the DC voltage. In a variable phase shifter having a high frequency input/output terminal, the resistance value R_ of the resistor connected in parallel with the variable capacitance diode
When A has the characteristic impedance of the variable phase shifter main body as Z_0 and the equivalent series resistance of the variable capacitance diode as R, then R_A=Z_0{1+√(1+4(R/Z_0)^2)
A variable phase shifter having a resistance value of /(2R/Z_0)}. 2. first and second variable capacitance diodes;
and a resistor having the resistance value R_A connected in parallel to each of the second variable capacitance diodes, a common control terminal that supplies DC voltage to the first and second variable capacitance diodes, and a common control terminal that supplies DC voltage to the first and second variable capacitance diodes. A hybrid circuit having two arms in which second variable capacitance diodes are respectively installed, an arm for inputting high frequency power, and an arm for outputting high frequency reflected power from the first and second variable capacitance diodes in phase. The variable phase shifter according to claim 1, characterized in that: