JPS646586Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a frequency characteristic equalization device that is installed in an amplifier that constitutes a television listening system and compensates for the frequency characteristics of a coaxial cable and an amplifier circuit. In general, in television public listening systems,
Signals are transmitted via coaxial cables, and signals transmitted via coaxial cables are attenuated more as the frequency is higher. Therefore, in the main line amplifier, branch amplifier, etc. in a television shared listening system, it is necessary to amplify to compensate for this attenuation and variations in the frequency characteristics of the individual amplifier circuits, and to obtain flat output characteristics. be. Therefore, conventionally, flat output characteristics have been obtained by changing the amount of feedback of the amplifier circuit in the amplifier according to the frequency of the signal. However, if the amplifier circuit is composed entirely of ICs,
Such a means cannot be used, and a frequency characteristic equalizer is connected to the input side of the amplifier circuit to perform compensation. As shown in FIG. 1, a reactance circuit 6 is connected between the input terminal 1 and the output terminal 2, in which a series circuit of a coil 3 and a capacitor 4 is connected, and a capacitor 5 is connected in parallel. A first terminal 11 and a second terminal 1 of a resistance attenuation circuit 10 in which resistors 7, 8, and 9 are connected in a π-shape to an output terminal 2.
2 are connected to each other, and a parallel circuit 17 of a coil 15 and a capacitor 16 is connected between the third terminal 13 of the resistance damping circuit 10 and the ground potential point 14. However, with this frequency characteristic equalizer, in order to change the frequency characteristic, it is necessary to replace the coils 3, 15, capacitors 4, 5, 16, etc., which causes variations in the frequency characteristics of individual amplifier circuits and tilt. It has been difficult to change the frequency characteristics according to the characteristics. This invention attempts to provide a frequency characteristic equalization device that can change the frequency characteristics to a certain extent. The frequency characteristic equalization device of this invention connects a reactance circuit consisting of a plurality of reactance elements between an input terminal and an output terminal, and has a π-type connection or a T-type connection, and has first to third terminals. The first and second terminals of the resistance damping circuit are connected to the input terminal and the output terminal, respectively, and a coil and a variable resistor are connected in series between the third terminal of the resistance damping circuit and a reference potential point. This circuit is characterized in that a parallel circuit in which capacitors are connected in parallel is connected to the circuit. With this configuration, by changing the resistance value of the variable resistor, the Q of the frequency characteristic equalizing device changes, and the frequency characteristic of the frequency characteristic equalizing device changes. Therefore, by simply changing the resistance value of the variable resistor, variations in frequency characteristics and tilt characteristics of individual amplifier circuits can be compensated for without replacing parts such as coils and capacitors. An embodiment of this invention will be described below based on FIG. 2. Regarding the same parts as the conventional example,
The same reference numerals are used, the specifications of each element are shown in the table below, and the description thereof will be omitted.

[Table] In Fig. 2, 18 is a variable resistor with a maximum resistance value of 100Ω, and this variable resistor 18 is connected to the coil 15.
A parallel circuit 17' is formed by a series circuit of the variable resistor 18 and the coil 15, and a capacitor 16 connected in parallel to the series circuit. The frequency characteristic equalizer configured in this way is
Its resonant frequency is higher than the highest usable frequency of this frequency characteristic equalizer. Then,
By changing the resistance value of the variable resistor 18, the Q of the frequency characteristic equalizer changes, and the frequency characteristic can be changed as shown in FIG. Therefore, variations in frequency characteristics and tilt characteristics of individual amplifier circuits can be easily compensated for without replacing parts. Note that instead of connecting the variable resistor 18 in series with the coil 15, the variable resistor 18 may be connected in series with the capacitor 16, or the variable resistor 18 may be connected between the parallel circuit 17 and the ground potential point 14. However, it is almost impossible to change the frequency characteristics. Further, although a π-type resistor attenuation circuit 10 is used, a T-type resistor attenuation circuit 10 may also be used.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional frequency characteristic equalizer.
FIG. 2 is a circuit diagram of an embodiment based on this invention, and FIG. 3 is a frequency characteristic diagram of the embodiment. 1... Input terminal, 2... Output terminal, {3... Coil, 4, 5... Capacitor} 6... Reactance circuit, {7... Resistor, 8... Resistor, 9... Resistor}
10...Resistance damping circuit, {15...Coil, 16
...Capacitor, 18...Variable resistor}17'...
...parallel circuit.

Claims (1)

[Scope of utility model registration request] A reactance circuit consisting of a plurality of reactance elements is connected between an input terminal and an output terminal, and the first and second resistive attenuation circuits are connected in a π-type connection or in a T-type connection and have first to third terminals. A parallel circuit in which terminals are respectively connected to the input terminal and the output terminal, and a capacitor is connected in parallel to a series circuit of a coil and a variable resistor between the third terminal of the resistance attenuation circuit and a reference potential point. Frequency characteristic equalization device formed by connecting.