JPH06216797A - High frequency variable slope tilt circuit - Google Patents

Abstract

PURPOSE:To provide an adjuster in which cost reduction can be attained and the correction of frequency characteristic can be easily performed and become an independent adjuster as a slope function by providing with a parallel circuit with a coil resistor connected in parallel with a capacitor via a variable resistor, and providing with a second capacitor between the connection point of third with fowrth resistors and an input terminal. CONSTITUTION:A first capacitor C1 connected between the input terminal 1 and an output terminal 2, and a first resistor R1 connected in parallel with the capacitor C1 are provided. Also, the parallel circuit between a first coil L1 connected in parallel with the capacitor C1 via the variable resistor R3 being the third resistor and a second resistor R2 is provided. Furthermore, the fourth resistor R4 connected between the resistor R3 and the ground 4, and the second capacitor C connected between the connection point of the resistors R3, R4 and the input terminal 1 are provided. By employing such constitution, it is possible to set the variable range of slope characteristic so as to fit to a CATV system in a state where loss in the low- or high-pass area of a transmission band is fixed by adjusting the resistance of the resistors R1, R2, and R4 and to increase/decrease tilt characteristic by the variable resistor R3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high frequency variable slope capable of fixing either the low band or the high band of the transmission band and continuously changing the slope of the frequency characteristic of the pass loss of the entire transmission band up and down. The present invention relates to a tilt circuit.

[0002]

2. Description of the Related Art A communication signal between stages of a high-frequency amplifier has a frequency characteristic of a pass loss of the entire transmission band in a state in which a change in loss amount in one of a low band and a high band is fixed at both ends of the transmission band. A circuit as shown in FIG. 16 is used as a tilt circuit for continuously changing the tilt. This circuit is a series circuit of a first coil L1 and a first capacitor C1 connected between an input terminal 1 and an output terminal 2, and a variable resistor that is a first resistor connected in parallel to this series circuit. Between the resistor R1 and a series circuit of the second resistor R2 and the third resistor R3 connected in parallel to the series circuit, and between the connection point of the second and third resistors R2 and R3 and the ground 4. Fourth
It is composed of a parallel circuit of a second capacitor C2 and a second coil L2 which are connected via a variable resistor R4 which is a resistor.

The passing loss characteristic of the tilt circuit of FIG. 16 is shown in FIG.
As shown in FIG. 7, when the tilt amount is minimum when the change in the loss amount in the high frequency band f2 of the transmission band is fixed, the characteristic is as shown by the solid line, while when the tilt amount is maximum, the characteristic is as shown by the broken line. Become. Here, by continuously changing the variable resistors R1 and R4, the frequency characteristic of the pass loss is inclined.

Such a tilt circuit is used in a line amplifier of a CATV system and works to compensate the frequency characteristic of the system. Here, the loss compensated by the line amplifier is roughly classified into a cable loss and a flat loss. The flat loss is due to the insertion loss of the branch, distributor, attenuator, etc., and has flat characteristics with respect to frequency. On the other hand, cable loss is a frequency characteristic (generally a
It is a loss having √f + bf), and in order to compensate for this, it is necessary to give the gain of the line amplifier a similar frequency characteristic. Cable equalizer (EQ) and slope control are used for this purpose.

By the way, in such a tilt circuit, the tilt amount of the frequency characteristic of the entire transmission band, that is, the loss amount is increased in a state where the change of the loss amount in either the low band or the high band is fixed. It is composed. However, in the CATV system, it is also necessary to reduce the loss amount. In this case, as shown in FIG. 18, such a tilt circuit 3 is combined with a high frequency transistor Tr, and the frequency characteristic (gain vs. frequency) of this high frequency transistor Tr is combined.
It is used to increase or decrease the amount of loss. Figure 1
FIGS. 9 to 21 show this state, and the frequency characteristic of the high frequency transistor Tr of FIG. 19 and the characteristic B of the variable tilt characteristic of FIG. 20 are combined to create the flat characteristic X of FIG. Further, the tilt characteristics Y and Z are created in a state in which the tilt circuit is changed to fix the high frequency range f2.

[0006]

As described above, by combining the conventional tilt circuit and the high frequency transistor, CA
When the tilt characteristic is increased or decreased so as to be suitable for a TV system, in order to realize a slope characteristic that can be changed up and down, in order to realize a slope characteristic of half the tilt amount in the tilt circuit and the gain of the reverse characteristic, A transistor circuit for giving a slope is required. Therefore, there is a problem that the circuit becomes complicated, a difficult adjustment is required to match the characteristics of the tilt circuit and the transistor circuit, and the cost increases due to an increase in the number of parts.

The present invention has been made in consideration of the above problems, and has a simple structure for cost reduction, facilitates correction of frequency characteristics, and has an independent adjuster as a slope function. It is an object of the present invention to provide a high-frequency slope tilt circuit that can be used as.

[0008]

In order to achieve the above object, the present invention provides a first capacitor connected between an input terminal and an output terminal, and a first capacitor connected in parallel with the first capacitor. And a parallel circuit of a first coil and a second resistor connected in parallel to the first capacitor via a variable resistor that is a third resistor, and between the third resistor and ground. And a second capacitor connected between a connection point of the third and fourth resistors and an input terminal.

Another aspect of the present invention is characterized by including a second coil connected between the input terminal and the ground in addition to the configuration of the above invention.

According to another aspect of the present invention, there is provided a first coil connected between an input terminal and an output terminal, a first resistor connected in parallel with the first coil, and a first coil connected to the first coil. Three
A parallel circuit of a first capacitor and a second resistor that are connected in parallel via a variable resistor that is a resistor, a fourth resistor that is connected between the third resistor and ground, The second connected between the connection point of the third and fourth resistors and the input terminal
And a coil.

Still another aspect of the present invention is that, in addition to the configuration of the above-mentioned invention, the second invention is connected between the input terminal and the ground.
And a capacitor of

[0012]

According to the structure of each invention, by adjusting the first resistance, the second resistance, and the fourth resistance, the change in the loss amount in the low band or high band of the transmission band is fixed, The variable range of the slope characteristic can be set so as to be suitable for the CATV system without using the high frequency transistor, and the tilt characteristic can be increased or decreased by the variable resistance. Further, the transmission bandwidth can be arbitrarily determined by selecting a coil and a capacitor which are reactance elements.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit configuration diagram showing a first embodiment of a high frequency variable slope tilt circuit of the present invention. The high frequency variable slope tilt circuit 10 of the present exemplary embodiment includes a first capacitor C1 connected between the input terminal 1 and the output terminal 2 and a first resistor R connected in parallel with the first capacitor C1.
1, a parallel circuit of a first coil L1 and a second resistor R2 connected in parallel to the first capacitor C1 via a variable resistor R3 which is a third resistor, and the third resistor R3. The fourth resistor R4 connected between the ground 4 and the third resistor
And a second capacitor C2 connected between the connection point of the fourth resistor and the input terminal 1.

FIG. 3 shows a second embodiment of the present invention. The high frequency variable slope tilt circuit 20 of this embodiment is
In addition to the circuit configuration of the first embodiment, a second coil L2 connected between the input terminal 1 and the ground 4 is provided. 2 and 4 show the frequency characteristics of the respective embodiments of FIGS. 1 and 3, and show the low band f1 of the transmission band.
In the high frequency range f2, it is possible to obtain the tilt characteristic including the inclination characteristics b and c that change in the vertical direction with respect to the flat characteristic a while the loss amount in the high frequency range f2 is fixed.

The loss amount of the flat characteristic a and the variable amounts of the slope characteristics b and c in the transmission band are determined by the first resistance R1,
The variable range can be set by adjusting the second resistor R2 and the fourth resistor R4. In the second embodiment of FIG. 3, especially outside the transmission band (below the low frequency range f1)
Signal can be blocked. In each of these embodiments, the variable amount of the tilt characteristics b and c is determined by the loss amount of the flat characteristic a. Conversely, the loss amount can be determined from the variable range. That is, when the tilt change amount is small, the loss amount of the flat characteristic a is also small. The variable range of the inclination characteristic b does not become larger than the loss amount of the flat characteristic a. That is, the variable range is determined by the loss amount of the flat characteristic a. Further, the values of f1 and f2 can be arbitrarily determined by selecting the constants of each of the components forming the circuit.

5 and 6 show the flat characteristic a and the slope characteristic b when the transmission band is set to two bands of 10 MHz to 50 MHz and 70 MHz to 300 MHz by selecting the constants of each component in the embodiment of FIG. It shows a specific frequency characteristic of c. 7 and 9 show frequency characteristics according to the second embodiment shown in FIG. 3 in which the coil L2 is added to the above-mentioned embodiment. That is, it is a specific frequency characteristic showing a state in which a signal outside the transmission band is blocked by the addition of the coil L2. Further, FIG. 8 is a specific frequency characteristic when the vertical variable range of the inclination characteristic is narrowed in the same transmission band as FIG. 7, and shows that the loss amount of the flat characteristic a is reduced.

FIG. 10 shows a third embodiment of the present invention. The high frequency variable slope tilt circuit 30 of this embodiment is
A first coil L1 connected between the input terminal 1 and the output terminal 2, a first resistor R1 connected in parallel with the first coil L1, and a third resistor connected to the first coil L1. A parallel circuit of a first capacitor C1 and a second resistor R2 connected in parallel via a variable resistor R3, and a fourth resistor R4 connected between the third resistor R3 and the ground 4. And a second coil L2 connected between the connection point of the third and fourth resistors R3 and R4 and the input terminal 1.

FIG. 12 shows a fourth embodiment of the present invention. The high frequency variable slope tilt circuit 40 of this embodiment is
In addition to the circuit configuration of the third embodiment, a second capacitor C2 connected between the input terminal 1 and the ground 4 is provided. FIGS. 11 and 13 show the frequency characteristics of the embodiments of FIGS. 10 and 12, and show flat characteristics in the low band f1 and high band f2 of the transmission band with the loss amount of the low band f1 fixed. It is possible to obtain the tilt characteristic including the tilt characteristics b and c that change in the vertical direction with respect to a.

Further, the loss amount of the flat characteristic a and the variable amount of the slope characteristics b and c in the transmission band are determined by the first resistance R1,
The variable range can be set by adjusting the second resistor R2 and the fourth resistor R4. In the fourth embodiment of FIG. 12, a signal outside the transmission band (above the high frequency band f2) can be blocked in particular. In addition, in these embodiments, the description about the cases of the first and second embodiments is applied in substantially the same manner. 14 and 15 show that the transmission band is 10 MHz to 50 M by selecting the constants of the respective parts in the third embodiment of FIG.
It shows specific frequency characteristics of the flat characteristic a and the inclination characteristics b and c when set to two bands of Hz and 70 MHz to 300 MHz.

[0020]

As described above, according to the present invention, the first resistor and the second resistor can be used without using a high frequency transistor.
By adjusting the resistance of and the fourth resistance, the change in the loss amount in the high band or low band of the transmission band is fixed,
The variable range of slope characteristics can be set to suit the CATV system, the tilt characteristics can be easily increased or decreased by the third variable resistor, and the frequency band itself can be easily adjusted by selecting constants of circuit components. It is possible to change the value to a variable value, to reduce the cost with a simple structure, and to use the slope function as an independent adjuster.

[Brief description of drawings]

FIG. 1 is a first high frequency variable slope tilt circuit according to the present invention.
2 is a circuit configuration diagram showing an embodiment of FIG.

FIG. 2 is an explanatory diagram of frequency characteristics of the first embodiment.

FIG. 3 is a circuit configuration diagram showing a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of frequency characteristics of the second embodiment.

FIG. 5 is a specific frequency characteristic diagram of the first embodiment.

FIG. 6 is a specific frequency characteristic diagram when the frequency band of the first embodiment is changed.

FIG. 7 is a frequency characteristic diagram of the second embodiment.

FIG. 8 is a specific frequency characteristic diagram when the vertical variable range of the inclination characteristic of the second embodiment is narrowed.

FIG. 9 is a specific frequency characteristic diagram when the frequency band of the second embodiment is changed.

FIG. 10 is a circuit configuration diagram showing a third embodiment of the present invention.

FIG. 11 is a frequency characteristic diagram of the third embodiment.

FIG. 12 is a circuit configuration diagram showing a fourth embodiment of the present invention.

FIG. 13 is an explanatory diagram of frequency characteristics of the fourth embodiment.

FIG. 14 is a specific frequency characteristic diagram of the third embodiment.

FIG. 15 is a specific frequency characteristic diagram when the frequency band of the third embodiment is changed.

FIG. 16 is a circuit configuration diagram showing a conventional tilt circuit.

17 is an explanatory diagram of frequency characteristics of FIG.

FIG. 18 is a circuit configuration diagram of a conventional variable slope tilt circuit.

19 is an explanatory diagram of frequency characteristics of the high frequency transistor in FIG.

20 is an explanatory diagram of frequency characteristics of the tilt circuit in FIG.

21 is an explanatory diagram of frequency characteristics created by the frequency characteristics of FIGS. 19 and 20. FIG.

[Explanation of symbols]

 C1, C2 Capacitor R1, R2, R4 Resistance R3 Variable resistance L1, L2 Coil f1 Low frequency f2 High frequency a Flat characteristic b, c Inclination characteristic 1 Input terminal 2 Output terminal 4 Ground

Claims (4)

[Claims] 1. A first capacitor connected between an input terminal and an output terminal, a first resistor connected in parallel to the first capacitor, and a third resistor connected to the first capacitor. A parallel circuit of a first coil and a second resistor connected in parallel via a variable resistor, a fourth resistor connected between the third resistor and ground, and the third and third resistors. 4. A high frequency variable slope tilt circuit comprising a second capacitor connected between the connection point of the resistor 4 and the input terminal. 2. A first capacitor connected between an input terminal and an output terminal, a first resistor connected in parallel to the first capacitor, and a third resistor connected to the first capacitor. A parallel circuit of a first coil and a second resistor connected in parallel via a variable resistor, a fourth resistor connected between the third resistor and ground, and the third and third resistors. High frequency variable slope tilt, comprising a second capacitor connected between the connection point of the resistor 4 and the input terminal, and a second coil connected between the input terminal and ground. circuit. 3. A first coil connected between the input terminal and the output terminal, a first resistor connected in parallel to the first coil, and a third resistor connected to the first coil. A parallel circuit of a first capacitor and a second resistor connected in parallel via a variable resistor, a fourth resistor connected between the third resistor and ground, and the third and third resistors. 4. A high frequency variable slope tilt circuit comprising a second coil connected between the connection point of the resistor 4 and the input terminal. 4. A first coil connected between the input terminal and the output terminal, a first resistor connected in parallel to the first coil, and a third resistor connected to the first coil. A parallel circuit of a first capacitor and a second resistor connected in parallel via a variable resistor, a fourth resistor connected between the third resistor and ground, and the third and third resistors. High frequency variable slope tilt, comprising a second coil connected between the connection point of the resistor 4 and the input terminal, and a second capacitor connected between the input terminal and ground. circuit.