JPS6343411A - Phase shifter - Google Patents

Abstract

PURPOSE:To obtain a phase shift amount close to 360 deg. immune from output fluctuation byt providing a series circuit comprising a capacitor and an inductor for phase shift setting and the 2nd series circuit comprising resistors and connected in parallel with the 1st series circuit. CONSTITUTION:A signal subject to phase shift is outputted to the 1st series circuit 2 and the 2nd series circuit 7 via a buffer amplifier 1. The phase of a difference (V1-V2) between the potential V1 at a connecting point of resistors 21, 22 and a potential V2 at a connecting point at an inductor 7 and a resistor 73 is 180+2tan<-1>(omegaL/R), where R is a resistance of the resistor 73. In bringing the resistor R to '0', the phase shift of the potential difference (V1-V2) with respect to the capacitance C of a variable capacitor 71 changed from '0' to infinite is 360 deg.. Since it is difficult to bring the capacitance of the variable capacitor 71 to '0' or inifinite, even when the minimum value C1 of the capacitance is larger than '0' and the maximum value C2 is definite, a larger phase shift is obtianed with the decreased resistance R by deciding the minimum value C1 and the maximum value C2 in the relation of (1/omegaC2)<omegaL<(1/omegaC1).

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase shift device that has a phase shift amount of nearly 360° and is free from output fluctuations due to changes in the phase shift amount.

[Conventional technology]

Figure 3 shows, for example, the "Electronic Communication Handbook" (1972).
FIG. 2 is a circuit configuration diagram showing a conventional phase shift device that can be easily imagined from the circuit diagram disclosed in the 2011 revised edition, page 132.

In the figure, 1 is a buffer amplifier, and 2 is a first series circuit, which is composed of a first resistor 21 and a second resistor 22. 3 is a second series circuit, which is composed of a third capacitor 31 and a variable resistor 32. 4 is a first capacitor, 5 is a second capacitor, and 6 is a differential amplifier.

Next, the operation of the conventional phase shifter shown in FIG. 3 will be explained. The phase-shifted signal is input to a buffer amplifier 1. The output of the buffer amplifier 1 is connected to the first series circuit 2.
is output to the second series circuit 3. Assume that the output signal of the buffer amplifier 1 is Vin, the angular frequency of the signal is W, the resistance values of the first resistor 21 and the second resistor 22 of the first series circuit 2 are both equal, and the If the capacitance value of the first capacitor 31 is C1 and the resistance value of the variable resistor 32 is Rv, then
The potential ■1 at the connection point between the first resistor 21 and the second resistor 22 of the series circuit 2 is as follows: V+ = +V i n −”・(1)
becomes. Also, the first capacitor 3 of the second series circuit 3
The potential 2 at the connection point between 1 and the variable resistor 32 is as follows. Therefore, the potential difference between each potential ■ and ■2 is Vl-=M””
exp(-j2tan wcRv) ・・・・・・(4
), and by changing the resistance value Rv of the variable resistor 32 from t-0 to a sufficiently large value, the potential difference vl-
The phase can be delayed from 0 degrees to approximately 180 degrees without changing the magnitude of v. Then, the potential difference vl−■
2 is taken out by a differential amplifier 6, amplified, and output.

Incidentally, it is desirable that the phase shift device has a phase shift amount of 360°. If a phase shift of 180° can be obtained as per the theory, by switching the output of the differential amplifier 6 between positive phase and negative phase,
A phase shift amount of 0° is obtained.

However, a phase shift of 180° cannot be obtained due to various factors. For example, it will be shown below that a phase shift amount of 180° cannot be obtained when the output resistance of the buffer amplifier is not 0 but is a finite value. Assuming that the output resistance of the buffer amplifier is Ro, the signal Vout applied to the first series circuit 2 and the second series circuit 3 is as follows: When Rν=O, when Rv=■, therefore, the phase of Vout 1Rv=0 is Delayed by the phase of Vin, Voutll? ν· is in phase with Vin. From the above, the input signal V when Rv=IIoo
The phase delay of the differential amplifier output signal with respect to in is 180°
Therefore, when Rv=O, the phase delay of the differential amplifier output with respect to the input signal Vin is Od'. Therefore, the phase shift amount is 180°-0d, which is less than 180°.

In addition, the amount of phase shift is further limited by the stray capacitance of the element and the inductance of the lead wire.

[Problem that the invention seeks to solve]

Since the conventional phase shift device is configured as described above, the phase of the buffer amplifier output signal Vout changes due to the change in the resistance value Rv of the variable resistor 32 due to the influence of the output impedance of the buffer amplifier.

There is also a problem that the amount of phase shift does not reach 180° due to the influence of stray capacitance of the element, inductance of the lead wire, etc.

This invention was made in order to solve this problem, and it is possible to reduce
The purpose is to obtain a phase shift device having a phase shift amount close to 0°.

[Means for solving problems]

The phase shift device according to the present invention includes a second series circuit, which includes a series circuit including a phase shift setting capacitor and a phase shift setting inductor, and a third resistor, and is connected in parallel with the first series circuit. Accordingly, a phase shift amount of nearly 360° is obtained by changing the phase shift setting capacitor or phase shift setting inductor.

[Effect]

In the phase shift device of this invention, the series connection of the phase shift setting capacitor and the phase shift setting inductor that constitute the second series circuit not only changes the reactance by changing the capacitance of the phase shift setting capacitor, for example, but also changes the reactance by changing the capacitance of the phase shift setting capacitor. Since the positive and negative sides can also be changed, it is possible to obtain a phase shift amount close to 360°.

[Embodiments of the invention]

FIG. 1 is a circuit diagram showing a phase shifter according to an embodiment of the present invention. In the figure, 1 is a buffer amplifier, 2 is a first series circuit, and a first resistor 21 and a second resistor 2
It is composed of 2. A second series circuit 7 includes a variable capacitor as a phase shift setting capacitor, an inductor as a phase shift setting inductor, and a third resistor.

4 is a first capacitor, 5 is a second capacitor, and 6 is a differential amplifier.

Next, the operation of the phase shift device shown in FIG. 1, which is an embodiment of the present invention, will be explained. The phase-shifted signal is input to a buffer amplifier 1. The output of the buffer 7 amble 1 is output to the first series circuit 2 and the second series circuit 7.

The angular frequency of the input signal of the buffer amplifier 1 is V in s signal is W, the resistance values of the first resistor 21 and the second resistor 22 of the first series circuit 2 are both R', and the second series circuit 7 Let the capacitance of the variable capacitor 71 be Cv, the inductance of the inductor 72 be L1, and the resistance value of the third resistor 73 be R.
This is the connection point with 3.

On the other hand, as described above, the first resistor 2 of the first series circuit 2
The potential V at the connection point between resistor 1 and second resistor 22 is as follows: Vl = engineering・Vin (
23), the potential difference vl-v2 is as follows.

FIG. 2 shows the relationship between the phase difference between v, -v2 and Vin and the capacitance Cv of the variable capacitor 71. In the figure, Cv is 0 →
If it can be changed as ■, then the phase of Vl-V2 is furthermore,
If R→O, then the amount of phase shift of v, -v2 with respect to Cv O→Flash is 360°, which is twice the amount of phase shift than the conventional device.

However, in actual variable capacitors, it is difficult to make the capacitance zero or ■'. Therefore, even if the minimum capacitance CI of the variable capacitor is larger than O and the maximum capacitance C2 is finite, if Cr and C2 are determined so that the third resistor 73 is The smaller the resistance value R is, the larger the amount of phase shift can be obtained. Therefore, by making R sufficiently small, a sufficient amount of phase shift can be obtained.

In the above embodiment, the variable capacitor 71 and the inductor 72 are used in the second series circuit 7, but a fixed capacitor and a variable inductor may be used, and the amount of phase shift may be adjusted by the variable inductor.

Furthermore, if a variable inductor is used instead of the inductor 72 of the second series circuit 7, the inductance of the variable inductance can be changed by changing the capacitance value of the variable capacitor to change the positive or negative of the reactance of the series circuit consisting of the variable capacitor and the variable inductor. Values are easily obtained.

〔Effect of the invention〕

As explained above, according to the present invention, the second series circuit is connected in parallel to the first series circuit, and the second series circuit is made up of a series circuit including a phase shift setting capacitor and a phase shift setting inductor, and a third resistor. With the circuit provided, the phase shift setting capacitor or phase shift setting inductor can be varied to obtain a phase shift amount close to 360'. Further, an excellent effect is achieved in that there is no accompanying fluctuation in amplitude.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, φ Fig. 2 is a diagram showing the relationship between the phase difference between the input signal and the output signal and the capacitance value of the variable capacitor, and Fig. 3 is a diagram showing the relationship between the phase difference between the input signal and the output signal and the capacitance value of the variable capacitor. FIG. 2 is a circuit configuration diagram showing a phase device. In the figure, 1 is a buffer amplifier, 2 is a first series circuit, 21 is a first resistor, 22 is a second resistor, 3 is a second series circuit, 31 is a third capacitor, 32 is a variable resistor, 4
is the first capacitor, 5 is the second capacitor, 6 is the differential amplifier, 7 is the second series circuit, 71 is the variable capacitor,
72 is an inductor, and 73 is a third resistor. In each figure, the same reference numerals indicate the same or corresponding parts. Agent: Masu Oiwa TA (and 2 others) Ka1 Figure 73: Fuji layer Uji mine Figure 2 Fuji 3 Figure 3; Series circuit 31 of Fuji 3; Capacitor 32 of rod 3;

Claims (6)

[Claims] (1) a first series circuit consisting of an amplifier to which an input signal subjected to a phase shift is input, and a first resistor and a second resistor connected in series, and connected between the output terminal of the amplifier and ground; a second series circuit consisting of a series connection of a phase shift setting capacitor, a phase shift setting inductor, and a third resistor and connected in parallel with the first series circuit; and the first resistor and the second resistor. A common connection point between the series circuit of the phase shift setting capacitor and the phase shift setting inductor and a second resistor is connected to the positive phase input terminal via the first capacitor, and a common connection point between the series circuit of the phase shift setting capacitor and the phase shift setting inductor and the second resistor is connected to the second capacitor. and a differential amplifier connected to an anti-phase input terminal via a phase shifter, the phase shifting device being characterized in that it obtains an output from the differential amplifier. (2) The phase shift device according to claim 1, wherein the phase shift setting capacitor is a variable capacitor. (3) The phase shift device according to claim 1, wherein the phase shift setting inductor is a variable inductor. (4) The phase shift device according to claim 1, wherein the phase shift setting capacitor and the phase shift setting inductor are comprised of a variable capacitor and a variable inductor. (5) The maximum absolute value of the reactance of the phase shift setting capacitor is greater than the reactance value of the phase shift setting inductor, and the minimum absolute value of the reactance of the phase shift setting capacitor is smaller than the reactance value of the phase shift setting inductor. A phase shift device according to claim 1, characterized in that: (6) The maximum reactance of the phase shift setting inductor is
The shifter according to claim 1, wherein the absolute value of the reactance of the phase shift setting capacitor is greater than the absolute value of the reactance of the phase shift setting capacitor, and the minimum value of the reactance of the phase shift setting inductor is smaller than the absolute value of the reactance of the phase shift setting capacitor. Phase device.