JPS6031405B2 - variable amplitude equalizer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a variable amplitude equalizer for use in communication equipment that allows the amount of attenuation to be easily varied.

Conventionally, a Bode type variable amplitude equalizer is known as a variable amplitude equalizer that can change the amount of attenuation so that attenuation and gain are symmetrically equal. FIG. 1 shows the circuit configuration of the Bode type variable amplitude equalizer. In the figure, 1 and 2 are input terminals, 3 and 4 are output terminals, N,, N2 are constant resistance circuits, G, ~
Q is conductance, Ga and Gb are variable conductances, V is input signal voltage, and V2 is output signal voltage. As is well known, the constant resistance circuits N, , N2 are composed of amplitude equalization circuits or all-pass circuits, and the circuits N, , N2 are inverse circuits to each other.

In Figure 1, when input terminals 1 and 2 and output terminals 3 and 4 are terminated with specified resistances, variable conductances Ga and Gb must be linked in order for the input/output impedance to become a constant resistance regardless of frequency. It is necessary to make changes. That is, Ga×Gb=certain condition is required. Therefore, in such a conventional Paude type variable amplitude equalizer, in order to change the amplitude characteristics while the impedance remains constant, the two variable conductances Ga and Gb must be changed equally, and the constant Two resistor circuits are required as shown by N, , N2, which has drawbacks in terms of adjustment and economy.
In order to eliminate these drawbacks, the present invention realizes a variable amplitude equalizer equivalent to the Paude type variable amplitude equalizer by using one variable conductance and one constant resistance circuit, and will be described in detail below.

FIG. 2 shows a first embodiment of the present invention, in which Q is an operational amplifier, 1 is an inverting input terminal of the operational amplifier Q, 1 is a non-inverting input terminal of the operational amplifier Q, and G, to G4 are conductance, Ga indicates the variable conductance, and the other signals are the first
Same as the figure.

As shown in the figure, input terminal 2 is grounded, and input terminal 1 is connected to the inverting input terminal 1 of the operational amplifier Q through the conductance G, and to the non-inverting input terminal + of the operational amplifier Q through the conductance G3. .

Further, the output of the operational amplifier Q is connected to the output terminal 3, and constitutes a circuit that applies feedback to the inverting input terminal of the operational amplifier Q through the conductance G2. On the other hand, a parallel circuit consisting of a constant resistance circuit N terminated with a variable conductance Ga and a conductance G4 is inserted between the non-inverting input terminal + of the operational amplifier and the ground, as shown in the figure. That is, the input signal from input terminal 1 is input to operational amplifier Q, through conductance G, 3,
The output of the operational amplifier Q is used as an output signal, and feedback is applied to the operational amplifier Q. On the other hand, amplitude equalization is performed using a constant resistance circuit N, a conductance G4, and a variable conductance Ga inserted between the non-inverting input terminal + of the operational amplifier N and ground. In FIG. 2, operational amplifier Q. If the admittance seen from the point a of the non-inverting input terminal 10 of the constant resistance circuit N, is YT, then the conductance G, = G2, and the voltage V of the input and output signals.
, , the relationship e8' of V2 is the following equation {1). e8=constant=-9 up...[1}G3-YT Now, in Figure 2, if the admittance seen from point b to the constant resistance circuit N side is Y, then the 0' equation becomes the following {2} equation. Can be rewritten.

e8 = constant = ≦ degree; Oji. Three Y. 10 take away G3 1 ---'2' The admittance Y, seen from the connection point b in Fig. 2 to the constant resistance circuit N, is C℃-Ga
...{3'P=If you put Sonakasuji, YI Ni G light・-pe-sha
...{4,・10pe-pine can be written.

Here, G°C is the characteristic admittance of the constant resistance circuit N, P
is the propagation constant of constant resistance circuit N.

Therefore, 7 = small ~ = ki -.・'51 as '4
', '5} expression, '2) expression is expressed as the following Tsukuda expression.

Now, if we let Qo be 8 when p=0 (Ga=Gb), (
In this case, 8' has only the real part Qo), which is given as follows. eQ.

=・17b≧30. ... Therefore, the formula {61 becomes the following formula (■).

Furthermore, eQ.

=-Top-...■? If we make it so that b--d, then we can derive the following formula.

Therefore, the three harmful poisons of summer and winter...-Holy Mother's Hand Peli P...(13) That is, Tsumugi-go-ko: tanh-gaku/pe-2P. (Suna) If we expand this equation, we get the following.

83 oaths*general science. ．． ．． (,.

Now, assuming that 0=Q1i8, the attenuation amount Q and the phase amount 3 are given as follows.

Clam side Jumono hology/pe-2AC.

Team.・・06) 8 Sa-Physics・OE-2 Small Wave .・
・(17) However, P=A+ship. (16), (17
) is exactly the same as that given by the Bode type variable amplitude equalizer, as is well known.

In other words, the attenuation of the equalizer is a constant term Qo and pe-2^c
It consists of a term proportional to the os wave, and the variable conductance G
If a is changed from 0 to 1, p is 11 to 11 from the glue formula.
Since it changes up to the standard value Qo,
^C.

S is in the process of changing the maximum amount of attenuation. (From 7' and ■ formula, G4
2-G32=○℃2...(18
), but this is the symmetrical conditional expression for this equalizer, and if it is satisfied, attenuation can be achieved as shown in equation (16) by changing the value of the variable element, that is, the variable conductance Ga. Characteristics can be varied.

That is, it is possible to realize characteristics equivalent to a Bode type variable amplitude equalizer. Furthermore, for the prescribed ○3 and Qo, C℃ and G4
is given as follows. Now, the constant resistance circuit N in Fig. 2,
If the circuit is a known circuit as shown in Fig. 3, then the second
The attenuation characteristic of the variable amplitude equalizer shown in the figure is as shown in FIG. Figure 3 shows a known amplitude equalization circuit.
is conductance, C, , C2 is a capacitor, L, is inductance, and other symbols are the same as in FIG. 2. Since this circuit configuration is well known, its explanation will be omitted, but the element values of this circuit are G...G.2=2. There is a relationship as follows: When the variable conductance Ga is equal to the conductance G°C, the input conductance of the constant resistance circuit N is equal to G°C regardless of the frequency, and the attenuation characteristic changes according to the frequency.

The attenuation characteristic of the variable amplitude equalizer shown in FIG. 2, which is the first embodiment of the present invention using such a constant resistance circuit N, is as shown in FIG.

That is, as shown in the figure, when the variable conductance ○a is open, the beautiful line shows the attenuation characteristic, and when it is short-circuited, the broken line shows the attenuation characteristic, and Ga=
In the case of W, a constant attenuation amount Qo is shown regardless of the frequency. Therefore, by changing the element value of the variable conductance Ga from 0, it changes continuously as shown by the arrow in the figure. That is, it is possible to realize characteristics equivalent to a Bode type variable amplitude equalizer that can vary the amplitude characteristics while keeping the impedance constant regardless of the frequency. As explained above, in the first embodiment of the present invention shown in FIG. 2, a variable amplitude equalizer equivalent to a Bode type variable amplitude equalizer is realized with one constant resistance circuit and one variable conductance circuit. This has the advantage that it is possible to achieve significant economicalization and that adjustment is extremely simple.

In the first embodiment, a constant resistance circuit N terminated with a variable conductance Ga is connected to an operational amplifier Q. I am looking for a circuit configuration to insert between the non-inverting input terminal 10 and the ground, but the 5th
As shown in the figure, a constant resistance circuit N, and a variable conductance G
a, the input terminal 1 and the non-inverting input terminal of the operational amplifier Q, +
A similar effect can be achieved by a configuration in which the conductance G4 is connected in parallel with the conductance G4. That is, as described above, the constant resistance circuit N and the variable conductance Ga are connected to the input terminal 1 and the operational amplifier Q. The conductance G3 is connected in parallel with the conductance G4 inserted between the non-inverting input terminal + of the operational amplifier Q, and the conductance G3 is inserted between the non-inverting input terminal + of the operational amplifier Q and ground. The other circuit configurations are the same as in the first embodiment.
In this second embodiment, the relationship between the input voltage V and the output voltage V2 is expressed by the following equation (21). V, G30 YT
...(21) V2 - G3 - Y D This only has one sign missing compared to the formula [1} explained in the first embodiment, so the input and output phases are reversed compared to the first embodiment. It is obvious that the characteristic as a variable amplitude equalizer exhibits the same effect as the first embodiment, only with the difference.

As explained above, the present invention can achieve characteristics equivalent to a Bode type variable amplitude equalizer with a circuit configuration with a small number of elements and only by adjusting one variable conductance, and has the advantages of economicalization and simplified adjustment. It can be widely used in communication equipment.

[Brief explanation of drawings]

FIG. 1 shows the circuit configuration of a conventional Bode type variable amplitude equalizer, FIG. 2 shows the circuit configuration of the first embodiment of the present invention, and FIG. 3 shows the circuit configuration of the first embodiment of the present invention.
FIG. 4 shows the attenuation characteristics of the first embodiment, and FIG. 5 shows the circuit structure of the second embodiment of the present invention. 1, 2...input terminal, 3, 4...output terminal, V. ...
...Input signal voltage, V2...Output signal voltage,
G, ~G4... Conductance, Ga, Gb・
...Variable conductance, N,, N2...
・Constant resistance circuit, Q. ...... operational amplifier, 1... inverting input terminal of operational amplifier Q, 10... operational amplifier Q
, non-inverting input terminal. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] 1 In the variable amplitude equalizer, one of the input terminals is grounded, and the other input terminal is connected so that the input signal is input to the inverting input terminal and non-inverting input terminal of the operational amplifier through the first and second conductances, respectively. , the output of the operational amplifier is connected to the output terminal and is connected to be fed back to the inverting input terminal of the operational amplifier through a third conductance, and between the non-inverting input terminal of the operational amplifier and ground. A constant resistance circuit terminated with a variable conductance is connected in parallel with the second conductance or the fourth conductance, and the square of the value of the second conductance and the fourth conductance are A variable amplitude equalizer characterized in that the difference between the square of the conductance value and the square of the characteristic admittance of the constant resistance circuit is made equal to the square of the characteristic admittance of the constant resistance circuit.