JPS59104814A - Phase separating circuit - Google Patents

Abstract

PURPOSE:To simplify the titled circuit and to reduce number of components by forming two phase shifters by a dual phase shift circuit using only one operational amplifier. CONSTITUTION:Variable resistors R17, R21 constitute an input separating circuit separating an input signal IN. Resistors R19, R20 consititute a gain setting circuit dividing the input signal IN and setting the gain of operational amplifiers 6, 7. The gain setting circuit is connected in common to eacg in-phase input terminal (non-inverting input terminal)+ of the operational amplifiers 6, 7. Thus, a prescribed phase difference is obtained at a broad frequency band around the center frequency. Thus, the circuit is simplified and the number of components is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a phase separation circuit, and more particularly to a phase separation circuit that separates an input signal into two output signals having the same amplitude and a constant phase difference using an active phase shifter using an operational amplifier. .

Conventionally, in this type of phase separation circuit, as method @1,
As shown in FIG. 1, there is a method of generating a constant phase difference by separating the input signals and passing the -power through a suitable phase shifter. Although this method has a simple circuit and requires fewer parts, it is not possible to obtain a constant phase difference over a wide frequency band because the amount of phase shift of the phase shifter changes depending on the frequency.

For example, in the circuit of FIG. 1, a=4R4, R1=Rg
When the focus C1=C2=C, the transfer function for the input of the output OU'l''l is expressed as follows, and from this, the phase difference 2 between the outputs 0UTI and 0UT2 is -z 4 xRc f'''' - 218' ``Shi V cat・------------
----------(2) where f is the frequency of the signal. As is clear from this equation, the phase difference greatly changes depending on the frequency, so the frequency of the input signal must be limited to a narrow range. Furthermore, since there is a phase shift of the operational amplifier itself, it is difficult to adjust the amount of phase shift.

A second method that improves the above drawbacks is a method in which the branched input signals are passed through independent phase shifters, as shown in FIG. In this method, the phase shifter is configured using a multi-stage phase shift circuit, and both phase shifters cancel out the fluctuations in the amount of phase shift, thereby reducing the phase difference between the outputs over a wide frequency band. The hill remains constant.

Figures 3(a) and (b) show the operating characteristics of the configuration shown in Figure 2.
As shown in Figure 3, the phase of the outputs 0UTI and 0UT2 relative to the input IN is 1231SOm, so even though there is a change in frequency (Figure 3 (a)), the difference can be kept almost constant over a wide frequency range B. It is possible (Fig. 3(b)).

For example, in the circuit shown in Figure 2, the phase difference between the outputs is approximately 9
Considering the case where it is set to 06, this field wave number,
When set, the transfer function Hz of output 0UT1.0UT2
(s), H (3) are respectively, and the phase difference between the outputs is as follows. However, X1=fx/fo, X=f/f.

becomes. An example of this numerical calculation is shown in Figure 5.
=0.29, b=51.95fo, fl=o, 59fo
, fx' = 1.6Bfo.

This shows the relationship between the phase difference DA and the frequency f when b'=0.14''%.As a result, the phase difference DA between the outputs is almost constant over a wide frequency range from approximately +fO to 3FO. It can be seen that the value is (90° in the middle).

However, this method uses a large number of operational amplifiers, which makes the circuit complicated, and at high frequencies,
Since errors due to the phase of the operational amplifier itself accumulate, it is difficult to obtain a designed phase difference. Furthermore, 2
Since the two phase shifters are completely separated, there is a drawback that the level of each output varies due to errors in the resistors.

The present invention has been made in order to eliminate the above-mentioned drawbacks of the conventional method, and therefore, an object of the present invention is to modify the method @2 and replace each phase shifter with a single operational amplifier.
The object of the present invention is to provide a new phase separation circuit which has a simplified circuit and a reduced number of parts by using a second phase shift circuit.

Another object of the present invention is to make it possible to reduce the level difference between the outputs to zero without being affected by errors in resistors, etc. by sharing the common-mode input terminals of the operational amplifiers of the two phase shifters. The object of the present invention is to provide a novel phase separation circuit that makes it possible.

In order to achieve the above object, a phase separation circuit according to the present invention includes an input separation circuit that separates input signals, and an input separation circuit that is connected to the input separation circuit and has a first phase relationship with respect to the input signal. a first phase shifter configured with an active quadratic phase shifter using a first operational amplifier; a second phase shifter configured with an active second-order phase shift circuit using two operational amplifiers; and a gain setting circuit to which common-mode input terminals of the first and second operational amplifiers are commonly connected. It is equipped with:

Next, a preferred embodiment of the present invention will be explained in detail with reference to the drawings.

FIG. 4 is a circuit configuration diagram showing an embodiment of the present invention. In the figure, reference symbol IN is an input signal, 0UT1.0UT
Reference numerals 2 and 7 respectively indicate output signals and operational amplifiers. Variable resistor &y and R1
1 constitutes an input separation circuit that separates the input signal IN. Resistors Rxo and Rso divide the input signal IN,
It constitutes a gain setting circuit that sets the gains of operational amplifiers 6 and 7. A gain setting circuit constituted by resistors Rx e and Rgo is commonly connected to each in-phase input terminal (non-inverting input terminal) of the operational amplifiers 6 and 7, as shown.

When Rho G = “'TCX’;; V = 'TTG,
f=f11fa=k"fxk: When set to any positive number, the transfer function for input signals of outputs 0UTI and 0UT2) (1(s), HbeS) is Hl(8)=G"1ψW-, , -11------
−−−−−−−−−1(6)(+2π )(+2π(a
) (S-2πfz') (8-2π"')----------------------
----------<7)) (g(s)=G-42.rl
+2g''), which is the same type as the transfer function of the circuit shown in Figure 2 above, except for the gain G of the operational amplifier. A constant phase difference similar to the circuit of FIG. 2 is obtained in the frequency band.

First, in the circuit of the present invention, since the operational amplifiers of each phase shifter share the common-mode input terminal, the outputs are 0UTI and 0U.
Both levels of T2 are determined solely by resistor R19. Therefore, it is related to the error of the resistor (・output 0
UTl and 0UT2 are at the same level.

As explained above, in the present invention, by configuring the two phase shifters with active quadratic phase shift circuits using only one operational amplifier, the number of parts can be reduced and the phase of the operational amplifier itself can be reduced. The phase error caused by the mouth is kept to a minimum.

Furthermore, by sharing the common-mode input terminal of each operational amplifier, there is no difference in level between the outputs, making it easier to adjust the output level.

[Brief explanation of the drawing]

1 and 2 are phase separation circuit diagrams according to the conventional method, FIG. 3 is a graph showing the principle of the phase separation circuit, and FIG. 4 is a circuit configuration diagram showing an embodiment of the phase separation circuit according to the present invention. ,
FIG. 5 is a graph in which the phase characteristics of the phase separation circuit are specifically calculated. 1.2.3.4.5.6.7...Operation amplifier, Rx,
Ra, -a@@m@m@”...Resistor, Cz, C example,,,1.,Cx1...Capacitor, 0UTI,
0UT2--Output of each phase separation circuit, IN--Input of each phase separation circuit Patent applicant: NEC Corporation Representative, Patent attorney Yutabe Kumagai

Claims (1)

[Claims] an active quadratic phase shift circuit connected to the input separation circuit and using a first operational amplifier so as to obtain a first phase relationship with respect to the input signal; a second phase shifter connected to the input separation circuit and configured to obtain a second phase relationship with respect to the input signal;
a second phase shifter configured with an active secondary phase shift circuit using an operational amplifier; and a gain setting circuit to which common-mode input terminals of the first and second operational amplifiers are commonly connected. A phase separation circuit characterized by comprising: