JPH0749876Y2 - Pseudo line circuit with frequency characteristic adjustment circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a pseudo line circuit used in a joint hearing device, and more particularly to a pseudo line circuit with a frequency characteristic adjusting circuit.

[Prior Art] Generally, a television broadcast signal or the like is transmitted by a coaxial cable in a main line or a branch line in a joint hearing device, and it is shown in FIG. As described above, a plurality of high frequency amplifiers 4, 4, ... Are cascade-connected in the coaxial cable 2.
However, the coaxial cable 2 is a so-called Since it has characteristics, it is not possible to obtain flat frequency characteristics simply by amplifying. So in the amplifier,
This is compensated by giving a so-called tilt characteristic.
Also, for coaxial cables Properties are also related to their length. Each high frequency amplifier 4,
Tilt characteristics of the coaxial cable 2 to be compensated by these amplifiers 4, 4 ... If the characteristics do not match, a pseudo line circuit 6 as shown in FIG. The characteristics are matched with the tilt characteristics of the corresponding amplifiers 4, 4, .... This pseudo line circuit 6 includes a resistor 1 connected in series between an input terminal 8 and an output terminal 10.
2 and 14, one end of a resistor 16 is connected to the interconnection point of these resistors 12 and 14, and the other end is grounded via a capacitor 18. Further, a series circuit of an inductor 20 and a resistor 22 is connected between the input terminal 8 and the output terminal 10.

[Problems to be solved by the invention] However, since the tilt characteristics of the amplifiers 4, 4, ... Are fixed, the frequency characteristics of the corresponding coaxial cable may not be completely compensated, and a slight deviation may occur. Occurs.
Moreover, such a deviation is added by each of the amplifiers 4, 4, .... For example, although point A shown in FIG. 6 has a flat frequency characteristic as shown in FIG. 8, slight variation occurs at point B as shown in FIG.
Large deviations occur as shown in Fig. 10. As a method of preventing such a large deviation, for example, a function for varying the tilt characteristic may be added to each of the amplifiers 4, 4, ..., However, recently, each of the amplifiers 4, 4 ,. ,
It tends to be unitized, and it has become impossible to add such a function to each of the amplifiers 4, 4, ....

The present invention aims to solve the above problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides an input terminal,
Between the output terminal, the pseudo line circuit provided between the input terminal and the output terminal, the pseudo line circuit provided between the input terminal and the output terminal, and between the input terminal and the output terminal Has a variable capacitance capacitor, a first inductor, and a series circuit of a first variable resistor. The pseudo line circuit includes a series circuit of a second inductor and a first resistor provided between the input terminal and the output terminal, and a series circuit provided between the input terminal and the output terminal. A series circuit of a second and a third resistor and a second and a third resistor
A fourth point provided between the connection point of the resistor of and the ground potential point
And a series circuit of a resistor and a capacitor.

In addition, a second variable resistor may be connected in parallel to the first inductor.

[Operation] According to such a solution, the resonance circuit is configured by the first and second inductors, the variable capacitors, and the capacitors. The frequency characteristic of this resonance circuit becomes a wave with three resonance frequencies. Then, the resonance frequency can be changed by changing the value of the variable capacitor, and the Q of the resonance circuit can be changed by changing the value of the first or second variable resistor. The slope can be changed.

[Embodiment] A first embodiment is shown in FIGS. 1 to 3. In this embodiment, as shown in FIG. 1, the pseudo line circuit 6 is connected to the input terminal 8
And the output terminal 10. This pseudo line circuit 6
Has the same configuration as the above-described conventional pseudo line circuit 6, the corresponding components are designated by the same reference numerals, and detailed description thereof will be omitted. In this embodiment, a series circuit including a variable capacitance element such as a semi-fixed capacitor 24, an inductor 26 and a variable resistor 28 is further connected between the input terminal 8 and the output terminal 10.

In the conventional pseudo line circuit, the inductor 20 and the capacitor 18 form a resonance circuit. This resonant circuit
Since it has a frequency characteristic represented by a quadratic equation, it has a single resonance frequency. The pseudo line circuit shown in FIG. 1 has a frequency characteristic represented by a quaternary equation because the inductor 20 and the capacitor 18 form a resonance circuit together with the semi-fixed capacitor 24 and the inductance 26. . Therefore, as shown in FIG. 2, it has a wavy frequency characteristic having three resonance frequencies (however, the lowest frequency of the three resonance frequencies is lower than 70 MHz, which is the lowest frequency used in the joint hearing facility). It is low, so it is not shown in FIG. 2). Then, by changing the value of the semi-fixed capacitor 24, the resonance frequency changes,
As shown in the figure, the frequency at which the output of the pseudo line circuit becomes 0 dB changes as shown by the arrow, and the slope of the frequency characteristic changes by changing the variable resistor 28, as shown by the phantom line in FIG. The output level changes at the resonance frequency.

The output of the conventional pseudo line circuit 6 which does not include the series circuit originally has a flat characteristic with a deviation of 0 as shown by the phantom line in FIG. As shown by the solid line, the peaks may fluctuate on the negative and positive sides. In such a case, the variable resistor 28
By adjusting, it is possible to approach a flat characteristic as shown by the dotted line. Also, by adjusting the semi-fixed capacitor 24, the semi-fixed capacitor 24, inductor
The resonance frequency of the resonance circuit formed by the capacitors 20 and 26 and the capacitor 18 changes, and as shown by the arrow in FIG.
Changes the frequency. Therefore, the semi-fixed capacitor 2
4. By adjusting the variable resistor 28, the frequency characteristic of the pseudo line circuit with the frequency characteristic adjusting circuit can be brought close to the flat characteristic of deviation 0 shown by the phantom line in FIG.

The pseudo line circuit with frequency characteristic adjusting circuit is housed in a rectangular parallelepiped case 29 as shown in FIGS. 3 (a) and 3 (b), and is provided on the front side thereof as shown in FIG. 3 (a). The semi-fixed capacitor 24 and the variable resistor 28 are adjusted by inserting an adjusting tool (not shown) through the circular windows 30 and 32. The input terminal 8 and the output terminal 10 are taken out in the shape of pins on the back side as shown in FIG. 34 is a ground potential terminal. The pseudo line circuit with the frequency characteristic adjusting circuit housed in the case 29 is attached to the pseudo line circuit attachment position of the amplifiers 4, 4, ... Formed on the printed circuit board in the case (not shown). The pseudo line circuit with the frequency characteristic adjusting circuit is not provided in all the amplifiers 4, 4, ..., but the output of each amplifier is actually monitored with the amplifiers 4, 4 ,. Based on the result, the amplifiers 4, 4, ... A normal pseudo line circuit is provided in the other amplifier 4. By providing in this way, it is possible to compensate for a large deviation of the frequency characteristic as shown in FIG.

A second embodiment is shown in FIGS. 4 and 5. This embodiment has the same structure as the first embodiment except that a variable resistor 36 is added in parallel with the inductor 26. The same parts are designated by the same reference numerals and the description thereof will be omitted.

According to the second embodiment, when the frequency characteristic becomes a shape having a peak only on the negative side as shown in FIG. 5, the variable resistor 36 is operated to change the frequency characteristic as shown by the dotted line. The deviation can be brought close to zero.

[Advantages of the Invention] As described above, the present invention includes a variable capacitance capacitor, a first inductor, and a first or first and second variable resistors in a pseudo line circuit having a second inductor and a capacitor. Since it is provided, it has a wavy frequency characteristic having three resonance frequencies. Then, the resonance frequency can be changed by adjusting the variable capacitor, and the slope of the frequency characteristic can be adjusted by adjusting the value of the variable resistor. Therefore, if the frequency characteristics of the coaxial cable cannot be compensated by the tilt characteristics of the amplifier used in the joint hearing device, and the frequency characteristics are wavy, a variable capacitor or variable resistor should be used. By adjusting, the frequency characteristic of the coaxial cable can be compensated. Therefore, even if the high-frequency amplifier is small and unitized and the frequency characteristic adjusting function cannot be added, the large deviation in the frequency characteristic that occurs in the latter stage of the plurality of cascade-connected amplifiers in the joint hearing device is prevented. Can be compensated. Further, since the pseudo line circuit is provided with a frequency characteristic adjusting circuit, even if a deviation in the frequency characteristic is found after the joint hearing device is completed as a system, instead of the normal pseudo line circuit, By using the pseudo line circuit with the frequency characteristic adjusting circuit according to the present invention, the deviation of the frequency characteristic can be compensated.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a first embodiment of a pseudo line circuit with a frequency characteristic adjusting circuit according to the present invention, FIG. 2 is a frequency characteristic diagram of the same embodiment, and FIG. 3 (a) is the first embodiment. FIG. 3 (b) is a side view of the first embodiment, and FIG. 4 is a second side view of the same.
FIG. 5 is a circuit diagram of the frequency characteristic circuit of the second embodiment, and FIG. 6 is a block diagram of a part of the joint hearing device.
FIG. 7 is a circuit diagram of a conventional pseudo line circuit, FIG. 8 is a frequency characteristic at point A in FIG. 6, FIG. 9 is a frequency characteristic diagram at point B in FIG. 6, and FIG. It is a frequency characteristic figure of C point. 6 ... Pseudo line circuit, 8 ... Input terminal, 10 ... Output terminal, 24 ... Semi-fixed capacitor (variable capacitor),
26 ... Inductor, 28 ... First variable resistor, 36 ... Second variable resistor.

Claims (2)

[Scope of utility model registration request] 1. A plurality of high-frequency amplifiers cascade-connected via a coaxial cable, which are provided in any of these high-frequency amplifiers, wherein an input terminal, an output terminal, and these input terminals and output terminals are provided. A pseudo-line circuit provided between the input terminal and the output terminal, and a first variable capacitance capacitor provided between the input terminal and the output terminal.
And a series circuit of a first variable resistor, and the pseudo line circuit includes a second inductor and a first resistor provided between the input terminal and the output terminal. A series circuit, a series circuit of second and third resistors provided between the input terminal and the output terminal, and second and third resistors
A fourth point provided between the connection point of the resistor of and the ground potential point
Pseudo-line circuit with a frequency characteristic adjusting circuit having a series circuit of a resistor and a capacitor. 2. A pseudo line circuit with a frequency characteristic adjusting circuit, wherein a second variable resistor is connected in parallel to the first inductor in the pseudo line circuit with a frequency characteristic adjusting circuit according to claim 1.