JPH0122262Y2 - - Google Patents

Description

[Detailed explanation of the idea]

The present invention relates to a frequency characteristic adjustment circuit, in which a circuit section including a coil and a capacitor, and a variable resistor constitute a resonant circuit, and a circuit is provided to vary the ratio of input signals supplied to the circuit section and the variable resistor. ,
It is an object of the present invention to provide a frequency characteristic adjustment circuit that can perform one-point adjustment when adjusting Q by changing only Q without changing the gain at the resonant frequency. FIGS. 1A to 1C show circuit diagrams of examples of conventional frequency characteristic adjustment circuits. In FIGS. 1A to 1C, 1 is an input terminal, 2 is an output terminal,
3 shown in FIG. 1C is a terminal to which a bias voltage is applied. The transfer function G of the circuits shown in FIGS. 1A to C is expressed as follows:
and the resonant angular frequency ω ₀ is

When the parameter Ω is set to Ω=ω/ω ₀ −ω ₀ /ω, it is expressed as the following equation. G=A+jQΩ/1+jQΩ (1) In this equation (1), A is the gain at ω=ω 0 when the gain at ω=0 and ω=∞ is ₁ , and Q is the figure of merit. Here, when the transfer function of each of the circuits shown in FIG. 1A to C is determined, and the gain A and figure of merit Q of each are determined, the circuit of FIG. 1A becomes as follows. The circuit in Figure 1B is The circuit in Figure 1C is It is expressed as This circuit of FIG. 1A is composed of 2a, 2
As is clear from equation b, A>1 and ω=
This is an emphasized type in which the gain A at the frequency of ω ₀ is maximum, and it is possible to change the gain A by changing only the resistance R ₂ and keeping Q constant. To change Q, use resistor R ₁ or capacitor C ₁ or coil
All you have to do is change L ₁ , but if you change capacitor C ₁ or coil L ₁ , the difference will be 1/√ _{1 1}
The resonant angular frequency ω ₀ expressed by changes,
If you change the resistance _R1 , the gain A will change,
Q with the gain A constant at the resonant angular frequency ωo
It is impossible to change only the Also the second
The circuit in Figure B is an attenuation type in which the gain A is minimum at the frequency where 0<A<1 and ω=ω ₀ , and the slider of the three-terminal variable resistor is connected to the collector of the transistor and the output terminal 2. and connect one end to capacitor C ₂ ,
The other end is connected to coil L ₂ to form resistors R ₃ and R ₄ . In this case, as is clear from Equations 3a and 3b, if you try to change the gain A by changing the resistor R ₃ or R ₄ , Q will change, and if you try to change the Q, you will change the capacitor C ₂ or the coil L _2. If , the resonant angular frequency ω ₀ expressed by 1/√ _{2 2} changes, and it is impossible to change only Q while keeping the gain A constant at the resonant angular frequency ω ₀ . In addition, the circuit in Figure 1C is of the emphasized or attenuated type, and as is clear from 4a and 4b, the resistance
It is possible to change the gain A by changing R ₇ or R ₈ while keeping Q constant. However, if the resistor R ₅ or R ₆ is changed to change Q, the gain A will change, and if the capacitor C ₃ or coil L ₃ is changed, the resonant angular frequency ω ₀ expressed as 1/√ _{3 3} will change. changes, making it impossible to change only Q while keeping the gain A constant at the resonance angular frequency ω ₀ . For this reason, Figure 1 A~
In order to adjust Q to a desired value in the conventional circuit shown in C, the gain A at the resonant angular frequency ω ₀ must also be changed, resulting in a two-point adjustment, which has the disadvantage that the adjustment work is complicated. Ta. The present invention eliminates the above-mentioned drawbacks, and each embodiment thereof will be described below with reference to FIGS. 2A and 2B. FIGS. 2A and 2B show schematic circuit diagrams of first and second embodiments of the frequency characteristic adjustment circuit according to the present invention, respectively. In FIG. 2A, 5 is an input terminal to which an input signal is received. This input terminal 5 is connected to an output terminal 7 via a series circuit consisting of an amplifier 6 with an amplification factor of A ₁ , a coil L ₄ and a capacitor C ₄ .
It is connected to the output terminal 7 via a variable resistor R _V1 provided in parallel with the series circuit, forming a series resonant circuit. This amplifier 6 is a variable resistor R _V1
This is a circuit for supplying input signals to coil L ₄ and capacitor C ₄ at a ratio of 1:A ₁ . Next, in FIG. 2B, the same parts as in FIG. 1A are given the same reference numerals. Here, in FIG. 2B, the input terminal 5 is connected to the output terminal 7 via a series circuit consisting of an amplifier 6 and a variable resistor R _V1 , and a coil L ₄ and a capacitor C are provided in parallel with this series circuit. _Four
It is connected to the output terminal 7 through a parallel circuit consisting of the following, and constitutes a parallel resonant circuit. Assuming that the voltage at the input terminal 5 is X, the voltage at the output terminal 7 is Y, and the degree of dewidth of the amplifier 6 is _A1 , the current I flowing from the amplifier 6 to the output terminal 7 is expressed by the following equation. I _{= A 1}
Since the current flows through the variable resistor R _V1 to the side, the following equation holds true. I=(Y-X)/R _V1 ...(21) From equations (20) and (21) above, A ₁ X-Y/jωL ₄ +1/jωC ₄ =Y-X/R _V1 jωC ₄ (A ₁ X-Y)/1-ω ² L ₄ C ₄ = Y-X/R _V1Here , by substituting ω ₀ ² = 1/L ₄ C ₄ , jωC ₄ (A ₁ X-Y)/1-ω ² /ω ² =Y-X/R _V1 jωC ₄ (A ₁ X-Y)/ω ² /ω-ω/ω ₀ =Y-X/R _V
1 Furthermore, by substituting Ω=ω/ω ₀ −ω ₀ /ω, we get jωC ₄ (A ₁ X−Y)/−Ω=Y−X/R _V1 jωC ₄ R _V1 (A ₁ X−Y)=(X _−Y ）Ω Y=Ω−jA ₁ ω _{0 C 4 R V1} ／Ω−jω ₀ C _{4 R V1 0} C ₄ Rv ₁ /1-Ω/-jω ₀ C ₄ Rv ₁ X Y _{= A 1} -j1/ω ₀ C ₄ Rv ₁ Ω/1+j1/ω ₀ C _{4 Rv 1} = Q ₁ , then Y=A ₁ −jQ ₁ Ω/1+jQ ₁ Ω (22) Comparing this equation (22) with equation (1), the following equation is obtained. In other words, when the transfer function of the circuit shown in FIG. 2A is in the form (1), the gain A in equation (1) depends only on the amplification degree _A1 of the amplifier 6, and similarly, the gain A in the circuit shown in FIG. The gain A of the circuit also depends only on the amplification degree A ₁ of the amplifier 6. Further, Q in each of FIGS. 2A and 2B is as shown in the following equation. Therefore, in the circuits shown in FIGS. 2A and B, it is possible to change the gain A while keeping Q constant by changing the amplification degree _A1 , and at the same time, it is possible to change the resistance value of the variable resistor R _V1 . Accordingly, it is possible to change Q while keeping the gain A constant at the resonant angular frequency ω ₀ (=1/√ _{4 4} ), and the above-mentioned adjustment of the gains A and Q can be performed by one-point adjustment. In addition, in FIG. 2A, the amplifier 6 may be placed between the input terminal 5 and the variable resistor R _V1 ,
In FIG. 2B, the amplifier 6 may be placed between the input terminal 5 and a parallel circuit consisting of a coil L ₄ and a capacitor C ₄ . In these cases, the amplification degree of the amplifier 6 is expressed as the reciprocal of the amplification degree _A1 in FIGS. 2A and 2B. 3A and 3B respectively show specific circuit diagrams of the circuit of FIG. 2A. Figure 3A is in emphasized form;
The input terminal 5 is connected to the base of a transistor T _r1 whose collector is connected to the power supply terminal 8 . The emitter of the transistor T _r1 is connected to the other end of a three-terminal variable resistor R _V2 whose one end is grounded.
A series-connected coil L ₄ is connected to the base of a transistor T _r2 whose collector is connected to the power supply terminal 8 via a capacitor C ₄ . Further, the collector of the slider of the three-terminal variable resistor R _V2 is connected to the base of the transistor T _r3 which is connected to the power supply terminal 8. The emitter of this transistor T _r3 is connected to the base of the transistor T _r2 via a variable resistor R _V1 for Q adjustment, and is also grounded via a resistor _R10 . The emitter of the transistor T _r2 is grounded and connected to the output terminal 7 via a resistor R ₁₁ . In this circuit, a three-terminal variable resistor R _V2 , a transistor T _r3 and a resistor
The amplifier 6 of FIG. 2A is configured by _R10 , and the resistance value between the emitter of the transistor _Tr1 and the base of the transistor _Tr3 of the three-terminal variable resistor _RV2 is made large (or small). By moving the slider in the direction, the amplification degree A ₁ can be increased (or decreased). Furthermore, Q can be made small (or large) by making the resistance value of the variable resistor R _V1 large (or small). In addition, if the gain A can be fixed, as shown in FIG. 3B, the three-terminal variable resistor R _V2 is changed to resistors R ₁₂ and R ₁₃ , and the transistor T _r3
Remove the variable resistor R _V1 at the connection point of resistors R ₁₂ and R ₁₃ .
The number of parts can be reduced by connecting one end of the When the transfer function of the circuit shown in FIG. 3B is transformed as shown in equation (1), the following equation is obtained. A=1+ _R12 / _R13 ...(7) As is clear from equations (7) and (8), this circuit is of the emphasized type, and it is possible to change Q by keeping the gain A constant at the resonance angular frequency ω ₀ by using the variable resistor R _V1 . . 4A and 4B show specific circuit diagrams of the circuit shown in FIG. 2B, respectively. FIG. 4A is of the emphasized or attenuated type, and the input terminal 5 is connected in series with a resistor R ₁₄ ,
It is grounded via _R15 and connected to the other end of a three-terminal variable resistor R _V3 whose one end is grounded. The connection point of the resistors R ₁₄ and R ₁₅ is connected to the base of the transistor T _r4 whose collector is connected to the power supply terminal 8, and the emitter of the transistor T _r4 is connected to the resistor R ₁₆
It is connected to the base of a transistor T _r5 whose collector is connected to the power supply terminal 8 via a parallel-connected coil L ₄ and a capacitor C ₄ . Furthermore, the collector of the slider of the three-terminal variable resistor R _V3 is connected to the base of the transistor T _r6 which is connected to the power supply terminal 8, and the emitter of the transistor T _r6 is grounded via the resistor R ₁₇ . , connected to the base of transistor T _r5 via variable resistor R _V1 . The emitter of the transistor T _r5 is grounded and connected to the output terminal 7 via a resistor _R18 . In this circuit, the amplifier 6 of FIG. 2B is configured by the transistor T _r4 and the resistors R ₁₄ to R ₁₆ , and further by the transistor T _r6 , the variable resistor R _V3 , and the resistor R ₁₇ as an emphasis or attenuation type circuit. There is. In this circuit as well, Q can be made large (or small) by making the resistance value of the variable resistor R _V1 large (or small). If the gain A can be fixed in the attenuated type, the input terminal is connected to the base of the transistor _Tr7 , and the emitter of the transistor _Tr7 is connected to the resistor R ₁₉ connected in series, It is possible to reduce the number of components by connecting it to the connection point of coil L ₄ and capacitor C ₄ and connecting one end of variable resistor R _V1 to the connection point of resistors _{R 19} and R ₂₀ . can. When the transfer function of the circuit shown in FIG. 4B is transformed as shown in equation (1), the following equation is obtained. A= _R20 / _R19 + _R20 ...(9) As is clear from equations (9) and (10), this circuit is of an attenuation type, and it is possible to change Q by keeping the gain A constant at the resonance angular frequency ω ₀ by R _V1 . Furthermore, in the circuits of FIGS. 2A and 2B, the gain A in equation (1) can be a negative value. When the group delay time τ is determined from this equation (1), it becomes as shown in the following equation. τ=QΩ ¹ /1 + Q ² Ω ² - (1/A) QΩ ¹ /1 + (1/
A) ² Q ² Ω ² ...(11) However, Ω=ω/ω ₀ −ω ₀ /ω, Ω ¹ =1/ω ₀ +ω ₀ /ω ² In this equation (11), Q>0, Ω ¹ >0, the group delay time τ becomes extremely large at ω=ω ₀ when the gain A is negative. Therefore, it can be used for special purposes such as circuits that compensate for phase and frequency characteristics. Note that the transistors T _r1 to _{T r7} in FIGS. 3A, B and 4 A, B are for impedance conversion, and are not necessarily necessary. As mentioned above, the frequency characteristic adjustment circuit according to the present invention includes a circuit section including a coil and a capacitor connected in series or parallel, and one terminal of which is connected to one terminal of this circuit section. The resonant circuit consists of a variable resistor and a circuit that supplies input signals to the other terminal of the circuit section and the other terminal of the variable resistor at different ratios, and generates resonance by changing the resistance value of the variable resistor. Since the frequency characteristics are adjusted by changing only the Q of the circuit, when adjusting only the Q to the desired value without changing the gain at the resonant frequency, only the variable resistor can be adjusted at one point, and only the gain mentioned above can be adjusted. In this case, one point adjustment can be made by simply changing the ratio of the input signals, and the adjustment work is simplified.

[Brief explanation of drawings]

Figures 1A to C are circuit diagrams of each example of a conventional frequency characteristic adjustment circuit, Figures 2A and B are schematic circuit diagrams of each embodiment of the circuit of the present invention, Figures 3A and B, and Figure 4A. , B are specific circuit diagrams of the circuits shown in FIGS. 2A and 2B. 5...Input terminal, 6...Amplifier, 7...Output terminal, 8...Power supply terminal, _C4 ...Capacitor, _L4 ...
... Coil, R _V1 ... Variable resistance.

Claims (1)

[Scope of utility model registration request] A circuit section including a coil and a capacitor connected in series or parallel, a variable resistor whose one terminal is connected to one terminal of the circuit section and forms a resonant circuit together with the circuit section, and the other side of the circuit section. and the other terminal of the variable resistor at different ratios, and by changing the resistance value of the variable resistor and changing only the Q of the resonant circuit, the frequency characteristics can be adjusted. Frequency characteristic adjustment circuit to adjust.