JPH01175307A - F1/2 gain adjusting circuit with tilt adjusting function - Google Patents

Abstract

PURPOSE:To give a tilt characteristic to a common audiovisual amplifier by adding two variable resistance elements to a tuning circuit. CONSTITUTION:A first and a second capacitors 16 and 18, two coils 6 and 12 and two resistors 8 and 10 constitute a tuning circuit sharing a first variable resistance element 14. That is to say, the first resistance element 14 exists in the tuning circuit and a second variable resistance element exists in parallel between the input and the output of the tuning circuit. When the resonance frequency of the tuning circuit is selected to near the upper limit frequency of a transmission band, a signal with many frequency components near the upper limit frequency and few frequency components near a lower limit frequency is generated at an output terminal 4. Thus, an output having the so- called tilt characteristic that the frequency components near the lower limit frequency are attenuated more largely than the frequency components near the upper limit frequency is generated.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a pressure gain adjustment circuit with a tilt adjustment mechanism provided in an amplifier used in a communal viewing device.

<Prior Art> Since the communal viewing and viewing amplifiers used in the communal viewing apparatus are connected to each other by coaxial cables, they are required to have gain characteristics that compensate for attenuation in the coaxial cables. In general, coaxial cables have so-called n-characteristics in which as the frequency increases, the attenuation increases in proportion to the square root of the frequency, as indicated by the symbol a in FIG. 10. Therefore, it is necessary for the amplifier for communal viewing and viewing to have a gain characteristic as shown in the figure without the reference numeral so as to compensate for this n-characteristic attenuation. Furthermore, since the amount of attenuation of this n-characteristic changes at a rate of 0.2%/'C with respect to temperature change, for example, as shown by the symbol C in the same figure, when the amount of attenuation of the n-characteristic changes, the As for the characteristics of the audiovisual amplifier, it is necessary to include a gain adjustment circuit having an n7 characteristic for changing the gain characteristics, as shown by reference numeral d in the figure.

In addition, coaxial cables have different attenuation characteristics depending on their type, as shown by the symbols e, f, and g in Figure 11. , i, and j, it is also necessary to provide a tilt adjustment circuit that makes the gains at the upper limit frequency the same and the gains at the lower limit frequency different.

Conventionally, a gain adjustment circuit and a tilt adjustment circuit having the above-mentioned n7 characteristics were separately provided in an amplifier for communal viewing and viewing.

<Problems to be Solved by the Invention> However, the conventional device had a problem in that the circuit configuration was complicated because a gain adjustment circuit and a tilt adjustment circuit each having a characteristic were provided.

Means for Solving the Problems> The present invention has been made to solve the above problems, and for this reason, the invention includes a first capacitor connected between an input terminal and a reference potential point, and a two coils connected in series between an input terminal and an output terminal, two resistors interposed in series between these coils, and a second resistor connected between the output terminal and the reference potential point. a first variable resistance element connected between the connection point of both of the resistors and the reference potential point, and a second variable resistance element connected between the input terminal and the output terminal. It is equipped with the following.

<Operation> According to the present invention, a tuning circuit that shares the first and second capacitors, two coils, and two resistors, or the first variable resistance element is configured.

That is, according to the present invention, the first variable resistance element is interposed within the tuned circuit, and the second variable resistance element is present in parallel between the input and output of the tuned circuit. When the resonant frequency of this tuning circuit is selected to be approximately the upper limit frequency of the transmission band, a signal is generated at the output terminal that has many frequency components near the upper limit frequency and few frequency components near the lower limit frequency. That is, an output having a so-called tilt characteristic is generated at the output terminal, in which the frequency component near the lower limit frequency is attenuated more than the frequency component near the upper limit frequency.

Here, when the first variable resistance element is adjusted, the degree of coupling between the circuit between the first capacitor and one coil and the circuit between the second capacitor and the other coil changes, so The amount of attenuation of the frequency component does not change, but the amount of attenuation of the lower limit frequency component changes. That is, the slope of the tilt characteristic changes. Further, when the second variable resistance element is adjusted, the amount of attenuation of the frequency component near the upper limit frequency and the lower limit frequency component changes, and thus the gain of the tilt characteristic changes.

<Embodiment> This embodiment has an input terminal 2 and an output terminal 4 as shown in FIG. The output terminal 4 is also connected to the input side of a wideband amplifier for communal viewing (not shown) having a flat frequency characteristic.

A series circuit of a coil 6, a resistor 8.10, and a coil IZ is connected between the input terminal 2 and the output terminal 4.

A variable resistance element 14 is connected between the connection point of the resistor 8.10 and the reference potential point. Also, input terminal 2 and base?
F! A capacitor 16 is connected between the potential point and a capacitor 18 is similarly connected between the output terminal 4 and the reference potential point. Further, a variable resistance element 20 is connected between the input terminal 2 and the output terminal 4.

Here, coil 6.12, capacitor 16.18 and 2
The two resistors 8 and 10 constitute a tuning circuit 21. The resonance frequency of this tuning circuit 21 is selected near the upper limit frequency of the tilt characteristic. Note that the resistor 8.10 is connected to a circuit consisting of the coil 6 and the capacitor 16, and the coil 1.
2. This is for adjusting the degree of coupling with the circuit consisting of the capacitor 18.

The variable resistance element 14.20 also includes a PIN diode 22 and a high frequency blocking coil 2, as shown in FIG.
4.26 and a DC blocking capacitor 28.30, and the passing loss may be adjusted according to the voltage supplied to the terminal 31, for example, the AGC voltage. As shown, the passage loss may be adjusted by using a variable resistor 32 and adjusting the position of its arm. As shown in Figure 4, when these variable resistance elements 14 and 20 are used alone, their frequency characteristics are flat in any frequency band, and when the loss increases, they shift in parallel to the larger loss. It is.

In this embodiment, when a signal with a constant level from the upper limit frequency component to the lower limit frequency component is supplied to the input terminal 2, since the tuning circuit 21 is provided, the output terminal 4 has many upper limit frequency components, and a lower limit frequency component. The frequency component between the two has a value intermediate between the two, and the signal flows. That is, this circuit has tilt characteristics as shown in FIG.

Here, the variable resistance element 14 is fixed, and the variable resistance element 20
When only the passing loss of the 9th
The gain of the tilt characteristic changes as shown by the solid line in the figure. Furthermore, if the variable resistance element 20 is fixed and only the passing loss of the variable resistance element 14 is adjusted, the degree of coupling between the circuit between the capacitor 16 and the coil 6 and the circuit between the capacitor 18 and the coil 12 changes, as shown in FIG. The slope of the tilt characteristic changes as shown by the dotted line. In addition, since resistor 8.10 is provided,
The adjustment range of the slope of the tilt characteristic is limited. Also,
By adjusting the variable resistance elements 14 and 20 together, the slope and gain of the tilt characteristics can be varied as shown in FIGS. 5 to 8.

Effect> As described above, according to the present invention, it is possible to provide a tilt characteristic to a communal viewing amplifier with a simple configuration in which two variable resistance elements are added to a tuning circuit.
It can also function as a gain adjustment circuit with special characteristics.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of one embodiment of a convex gain adjustment circuit with a tilt adjustment function according to the present invention, FIG. 2 is a circuit diagram showing an example of a variable resistance element used in the same embodiment, and FIG. 3 is a circuit diagram of an embodiment of the same embodiment. A circuit diagram showing another example of the variable resistance element used in the example, Fig. 4 is a frequency characteristic diagram of the variable resistance element used in the same example, and Figs. 5 to 9 are adjustment of the variable resistance element of the same example. Figure 10 shows the frequency characteristics of coaxial cables and the frequency characteristics provided by the amplifier to compensate for them. Figure 11 shows the frequency characteristics of various coaxial cables and their frequency characteristics. FIG. 3 is a diagram showing the frequency characteristics of an amplifier for compensating for. 2...Input terminal, 4...Output terminal, 6.12.
... Coil, 8, lO... Resistor, 14.20.
...variable resistance element, 16.18...capacitor. Companion bull applicant DAY

Claims (1)

[Claims] (1) A first capacitor connected between the input terminal and the reference potential point, two coils connected in series between the input terminal and the output terminal, and intervening in series between these coils. two resistors, a second capacitor connected between the output terminal and the reference potential point, and a first variable capacitor connected between the connection point of both the resistors and the reference potential point. A √f gain adjustment circuit with a tilt adjustment function, comprising a resistance element and a second variable resistance element connected between the input terminal and the output terminal.