JPS6237570B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention provides a common receiving amplifier such as a main line or main line branch amplifier, when the length of the transmission line (coaxial cable) connected to the input side is shorter than a predetermined length. Signals for joint reception (TV signals, FM broadcast signals) that compensate for the length of the cable and reach the same state as if a cable of a specified length were used.
The present invention relates to an attenuator used when attenuating.

In this type of attenuator, the higher the frequency, the greater the amount of attenuation that must be exhibited, so conventionally a large number of resistors were used as shown in Figure 4.
It was composed of a combination of R ₁ , R ₂ , R ₃ , R ₄ , coil L ₁ , and capacitor C ₁ . However, with a structure using such a coil, after the attenuator is assembled, the coil L ₁ must be adjusted to obtain the attenuation amount with the predetermined √ characteristic, and the adjustment work is extremely troublesome. It had the disadvantage of being. Furthermore, if such adjustment is omitted, a problem arises in that the attenuation characteristics of a large number of attenuators differ from each other.

SUMMARY OF THE INVENTION The present invention aims to eliminate the above-mentioned drawbacks and to provide a pseudo-line attenuator for a transmission line that can provide predetermined and uniform characteristics with simple assembly work.

The drawings showing the embodiments of the present application will be described below. In FIG. 1, numeral 1 indicates the center conductor, and a normal copper wire such as a polyurethane copper wire, an enameled copper wire, or a vinyl-covered copper wire is used. 2 indicates the input end, and the transmission line on the input side (for example, the center conductor of a coaxial cable)
Alternatively, various circuits connected to the input side of the amplification section of the amplifier are connected. Incidentally, the impedance of this input terminal 2 is set to have a value equal to or approximate to the impedance of the transmission line or other connected circuit. Reference numeral 3 indicates an output terminal, which is a terminal for sending a signal to a next-stage circuit, such as an amplifier circuit, and its impedance is set to a value equal to or approximately equal to the impedance of the next-stage circuit. (e.g. 75
Ω) 4 represents a ground conductor, 5 represents its input end, and 6 represents its output end. The ground conductor 4 is connected to an external conductor of a transmission line or a ground conductor of various electronic circuits. Next, 7 is the center conductor 1
The series arm element is shown interposed in the figure. In this series arm element 7, 8 is a ferrite core, 9, 1
0 indicates the through holes drilled in the core 8, and these include the input side center conductor 1 constituting the center conductor 1.
1. The output side center conductor 12 is inserted through each.
The center conductors 11 and 12 are connected in series, and 13 indicates a connecting portion thereof. The ferrite core 8 has such a property that the center conductor inserted through the through hole has a resistance value that increases as the frequency increases, for example, as shown in FIG. 2. A material having the following characteristics is used. Further, its dimensions are, for example, an outer diameter of 5 mm or 6 mm, a length of 5 mm, and an inner diameter of the through hole of 1 mm. Next, reference numeral 15 denotes a parallel arm element, one end 16 of which is connected to the connection part 13 in the series arm element 7, and the other end 17 connected to the ground conductor 4. Note that the connection at one end 16 indicates a connection to a connection portion between the input-side central conductor 11 and the output-side central conductor 12 in an electrical sense. In this parallel arm element 15, 18 is a capacitor, 19 is a resistive element, and these are mutually connected in parallel as shown. The resistance element 19 is constructed by inserting a conductor 22 into a through hole 21 of a ferrite core 20. For the ferrite core 20, a material is used for the conductor 22 inserted through the through hole 21, which has a property that a constant resistance value can be obtained regardless of the frequency. The dimensions are, for example, the outer diameter
3.5 mm, the length is 7 mm, and the inner diameter of the through hole is 1 mm.

In the above configuration, a high frequency signal (TV signal) entering the input end 2 from a coaxial cable or other circuit passes through the series arm element 7, appears at the output end 3, and is sent to the next stage circuit. . A portion of the signal also escapes from the series arm element 7 through the parallel arm element 15 to ground. In this case, since the series arm element 7 is constructed using the above-mentioned material, its impedance increases as the frequency increases, and the parallel arm element 1
5 uses a capacitor 18, so its impedance has a frequency characteristic that is inversely related to that of the series arm element 7, and its value decreases as the frequency increases. Therefore, the signal that enters from the input terminal and is sent out from the output terminal 3 is attenuated more greatly as the signal is in a higher frequency range (attenuated by the attenuation characteristic of the √ characteristic), and the signal level becomes smaller. sent from.

In the case of signal transmission as described above, the resistance element 19 in the parallel arm element 15 has a ferrite core 2.
Since 0 is used, the impedance of the resistive element 19 becomes almost zero in the lightning frequency range, and therefore it functions as a lightning arrester and prevents the element from being burnt out. Therefore, the next stage circuit connected to the output terminal 3 can also be protected.

Next, FIG. 3 shows an example of a usage state of the attenuator having the above configuration, and shows an example in which the attenuator is connected between the input terminal 25 of the communal reception amplifier and the amplifying section 26 via the changeover switch 27. It is something. Sho 28
indicates an output terminal.

In the above configuration, if the length of the coaxial cable (transmission line) connected to the input terminal 25 is a predetermined length (the length at which the planned attenuation occurs in the design), all switches are turned off. Switch to the OFF side. Then, the signal that has entered the input terminal 25 is transmitted as it is to the amplifying section 26, and the signal amplified by the amplifying section 26 is output from the output terminal 28. Further, if the length of the coaxial cable connected to the input terminal 25 is short, an appropriate number of the plurality of switches 27 are switched to the ON side as shown in the figure, depending on how short the coaxial cable is. Then, the signal that enters the input terminal 25 passes through two attenuators, and a signal whose level and frequency characteristics are the same as in the case where the length of the cable is a predetermined length is input to the amplification section 26. .

As described above, in this invention, even when the cable length on the input side is short and the expected attenuation cannot be obtained in the cable on the input side, the attenuation characteristic is the same as that of a coaxial cable. The transmission signal can be attenuated by the characteristic attenuation characteristic, and this has the effect of making it possible to send an appropriate signal to the next stage while compensating for the cable length.

Moreover, in the present invention, even if the structure has the same attenuation characteristics as the above-mentioned coaxial cable,
Since the series arm element 7 can be formed simply by attaching ferrite cores 8 of a unique shape to the center conductors 11 and 12 on the input side and output side of the series arm element 7, the means for forming it is as follows. It has the advantage of being extremely simple (there is no need for the trouble of adjusting the reactance of the coil as in the case of using conventional coils), and it goes without saying that it can be assembled extremely quickly. Its shape is extremely small, which contributes to the miniaturization of equipment.Furthermore, it reduces the number of elements that make up the parts, contributing to cost reduction, and furthermore, the electrical characteristics of each product are uniform. This has a revolutionary effect in making this type of attenuator high-quality and inexpensive. To repeat further, the present invention has two central conductors on the input end side and the output end side, and also has a ferrite core equipped with two through holes in parallel. Each of the above two center conductors is inserted into each one, and one end of each of the two center conductors outside the through hole is connected to each other, and the other end is connected to the input end and the output end, respectively. In addition, the ferrite core is constructed of a ferrite core that has a property of being able to obtain a resistance value that increases as the frequency of the high frequency wave passing through it increases with respect to the center conductor. , These constitute a series arm element, and on the other hand, a conductor is inserted through the capacitor and its through hole so that the impedance decreases as the frequency increases, with frequency characteristics having an inverse numerical relationship with the above series arm element. Since the parallel arm element is configured by connecting the ferrite cores in parallel, the series arm element 7 only needs to add one ferrite core 8 to the line, and the parallel arm element 15 is connected to the capacitor 18. and ferrite core 20
It is extremely useful in terms of drastically reducing the number of parts and reducing assembly man-hours.

Moreover, for signal transmission, parallel arm elements 15
Since the ferrite core 20 is used in the device, its impedance becomes almost zero in the lightning frequency range, so it functions as a lightning arrester and has the effect of preventing element burnout. Therefore, output end 3
It also has the revolutionary effect of protecting the next stage of circuitry connected to the circuit.

[Brief explanation of the drawing]

The drawings show an embodiment of the present application, and FIG. 1 is a perspective view of an attenuator, FIG. 2 is a graph showing the relationship between frequency and resistance value, and FIG. 3 is a circuit diagram showing the state of use.
FIG. 4 is a circuit diagram showing a conventional example. 1... Center conductor, 11... Input side center conductor, 12...
Output side center conductor, 7...Series arm element, 8...Ferrite core, 15...Parallel arm element.

Claims (1)

[Claims] 1 It has two center conductors on the input end side and the output end side, and also has a ferrite core equipped with two through holes in parallel, and these two through holes each have the above two center conductors. One end of each conductor is inserted through each of the two central conductors, and one end of each of the two center conductors outside the through hole is connected to each other, and the other end is connected to the input end and the output end, respectively. The ferrite core is composed of a ferrite core that has the property of being able to obtain a resistance value that increases as the frequency of the high frequency wave passing through increases with respect to the above-mentioned center conductor. On the other hand, the ferrite core is made up of a capacitor and a conductor inserted through its through hole so that the impedance decreases as the frequency increases, with frequency characteristics having an inverse relationship with the series arm element. A parallel arm element is constructed by connecting these in parallel, and one end of the parallel arm element is
Connect the center conductors of the input end side and the output end side to the mutually connected side, and connect the other end to the ground conductor to set the impedance of the series arm element and the parallel arm element, respectively, between the two centers. A pseudo-line attenuator for a transmission line, characterized in that the impedances have frequency characteristics that are inversely related to each other so that a signal passing through the conductor has an attenuation amount of √ characteristic.