JPS63122308A - Phase shifter - Google Patents

Abstract

PURPOSE:To decrease number of resistors relating to the time constant by supplying an input signal and an output signal of a low pass filter to a subtraction circuit, giving the difference of the signals to a mixer so as to control the mixing ratio of the mixer. CONSTITUTION:A signal fed to an input terminal 1 is connected to ground through a series circuit comprising a resistor 2 and a capacitor 3. Thus, a low frequency component L is extracted from a connecting point between the resistor 2 and the capacitor 3 and fed to one input of a mixer 4 whose mixing ratio is variable. Moreover, the signal from the input terminal 1 and the signal of the low frequency component from the connecting point are fed to a subtractor circuit 5, where the low frequency component is subtracted from the input signal. Thus, a high frequency component H of the input signal is extracted at the output of the subtraction circuit 5 and fed to the other input of the mixer 4. Then the mixing ratio (a) of the mixer 4 is controlled by a signal from a control terminal 6 and the mixed output is extracted at an output terminal 7. Since only one resistor gives effect on the characteristic in this way, excellent phase shift is executed easily by having only to provide a circuit correcting the dispersion of the resistor.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a phase shifter that can arbitrarily phase shift a human signal by, for example, voltage control.

[Requires 8% of the invention] The present invention relates to a phase shifter, and by using a low-pass filter and a subtraction circuit, the number of resistors related to the time constant can be reduced to riI.
It was designed to reduce the amount.

[Conventional technology]

As a phase shifter capable of arbitrarily shifting the phase of a human input signal, the one shown in FIG. 3 is known.

That is, in the figure, current sources (31) (32) are provided that form current signals of aI and (1-a)I, where a is a coefficient, for a human input signal (I), and this current source (3
1) A resistor (33) with a resistance value R is connected in parallel to (32) (
34), and the end of the current source (31) is connected to a buffer amplifier (35) and a capacitor (36) with a capacitance of C.
) to the end of the current source (32).

And in this circuit, current sources (31) (32)
If the potentials at the toes of are respectively V 1 r V 2, then the relational expression ■1 tremor alR is established, and from these expressions, 1+JωCR, when a-1, 3 wm, and Q, a-0,5. When V2 = 0.5IR (7 attenuators), a characteristic is obtained. In other words, the gain characteristic diagram is as shown in Figure 4A, whereas the phase shift characteristic diagram is as shown in Figure 4B, where the center frequency fc is +45° at a-1.
, a ″O, a phase shift of −45° can be performed.

However, in this circuit, resistors (33) (34
) may vary in resistance value by about ±20% when integrated into an IC, and this may cause the range of change in phase shift to fluctuate. In response to this, an internal/external conversion method was proposed to absorb variations in resistors within an IC (Japanese Patent Laid-Open No. 1983-1999).
(Refer to No. 261209) However, as mentioned above, if there are two resistors that require this correction, two sets of configurations are required for internal/internal conversion, making the configuration extremely complicated. was.

[Problem that the invention seeks to solve]

As mentioned above, in the conventional technology, since there are two resistors that affect the characteristics, two sets of circuits are required to compensate for this variation, resulting in an extremely complicated configuration. .

[Means for solving problems]

In the present invention, an input signal (#i (■)) is passed through a low-pass filter consisting of a series circuit of a resistor (2) and a capacitor (3) to one side of a mixer (4) with a variable mixing ratio. input, the human input signal and the output signal of the low-pass filter are supplied to a subtractor circuit (5), and this difference signal is supplied to the other input of the mixer to control the mixing ratio of the mixer (
terminal (6)) to obtain an arbitrarily phase-shifted output signal (
This is a phase shifter with a terminal (7).

[Effect]

According to this, since there is only one resistor that affects the characteristics, it is possible to easily perform a good phase shift simply by providing a circuit for correcting this variation.

〔Example〕

In FIG. 1, (11 is an input terminal, and a signal supplied to this input terminal (1) is grounded through a series circuit of a resistor 'a (2) and a capacitor (3). 2) and the capacitor (3), the low frequency component (L) of the human power signal is taken out, and this low frequency component signal is supplied to one of the human power signals of the mixer (4) with a variable mixing ratio. Further, the signal from the input terminal (1) and the signal of the low frequency component from the above-mentioned connection center point are supplied to the subtraction circuit (5), and the low frequency component is subtracted from the human input signal.

As a result, the high frequency component (H) of the human input signal is extracted from the output of the subtraction circuit (5), and this high frequency component signal is sent to the mixer (
4) is supplied to the other manpower. And this mixer (4
) is controlled by a signal from the control terminal (6), and this mixed output is taken out to the output terminal (7).

That is, in this circuit, the resistance value of resistor (2) is R
1 The capacitance value of capacitor (3) is C, and the input signal is VI
If N, then the relational expression I VIN 1 + jωCR VIN VIN 1 + jωCR holds true, and here the output signal Vo is expressed as Vout = (1
-a) L+aH then VO(JT (1-a) +a j (1)CR
VIN! +JωCR.

Therefore, in this circuit, when a=l, it becomes a low-pass filter characteristic, when a-Q, it becomes a bypass filter characteristic, and when a-0,5, it becomes an attenuator characteristic with a gain of 0.5, which is the same gain as in the conventional example described above. By controlling the value of a, -45° to +45°
A phase shift of ° can be performed.

In this way, it is possible to perform the same phase shift as in the conventional example, but since the above-mentioned circuit uses only one resistor, by correcting this variation using the inside/outside conversion method, etc., it is possible to achieve a simple configuration. A good phase shift can be performed.

In addition, according to the above circuit, since the other end of the capacitor (3) is grounded, there is no fear that parasitic capacitance etc. will affect this capacitor, and the capacitance value of this capacitor can be switched, for example, to generate a chroma signal of a video signal. When the phase shift of ζ is performed, switching between the NTSC system and the PAL system can be easily performed.

Note that FIG. 2 shows a specific example of a circuit, and in this figure, parts corresponding to those described above are given the same reference numerals. That is, in the figure, a signal from input terminal +11 is supplied to a resistor (2) and a capacitor (3) through an emitter follower (11), and a signal at the middle point of this connection is supplied to a transistor (52) (53) that constitutes a differential amplifier, respectively. ) is supplied to the base. A subtraction circuit (5) is formed by supplying the signal from the emitter follower (11) to the base of the other transistor (51) of one differential amplifier, and a subtraction signal (H) flowing through the transistor (52) is formed. is supplied to differentially connected transistors (41) and (42). Also, the other transistor (5
A constant voltage is supplied from the emitter follower (12) to the base of the transistor (4), and the signal (
L) are differentially connected transistors (43) (44
). Furthermore, the control signal from the control terminal (6) is transmitted to the transistor (61) (6) that constitutes the differential amplifier.
2)' is supplied to the base of this transistor (61
) is supplied to the bases of the transistors (42) (43).

Also, a signal corresponding to the mixture ratio (1-a) obtained at the drain of the transistor (62) is transmitted to the transistor (41).
(44) is supplied to the base. and a transistor (
The drains of transistors (41) (43) are connected to each other, and the drains of transistors (42) (44) are connected to each other, so that this transistor (42) (
A mixed output of (1-a)L+aH is taken out to the output terminal (7) from the connection midpoint of the drain of (44).

Thus, in this circuit, the mixer (4), the subtraction circuit (
5) etc. are formed, and the signal supplied to the input terminal (1) is phase-shifted in accordance with the control signal from the control terminal (6) and taken out to the output terminal (7). This makes it possible to realize the circuit described above.

〔Effect of the invention〕

According to this invention, since there is only one resistor that affects the characteristics, it is now possible to easily perform a good phase shift simply by providing a circuit to correct this variation.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 and 4 are diagrams for explaining the conventional technology. (1) is an input terminal, (2) is a resistor, (3) is a capacitor, (4) is a mixer, (5) is a subtraction circuit, (6) is a control terminal, and (7) is an output terminal. Hidemori Matsukuma

Claims (1)

[Claims] An input signal is supplied to one input of a mixer with a variable mixing ratio through a low-pass filter consisting of a series circuit of a resistor and a capacitor, and the input signal and the output signal of the low-pass filter are combined. A phase shifter, the difference signal being supplied to a subtraction circuit and supplied to the other input of the mixer, and controlling the mixing ratio of the mixer to obtain an arbitrarily phase-shifted output signal.