JPH0321067Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a television signal splitter that has excellent electrical characteristics over a wide frequency band.

[Technical background of the invention and its problems]

A public listening system for television signals in a building or the like is known, for example, as shown in FIG. In the figure, 1 is an antenna, and the television signal is transmitted from this antenna 1 through a 2-way splitter 2 installed in building A, and then connected in series to branchers 3, 4, and 8, and to terminal splitters 9 and 10, respectively. Connected.

Here, the circuit of the terminal distributors 9 and 10 includes, for example, an impedance matching transformer 20 whose one end is grounded, and a transformer 20, as shown in FIG.
A distribution transformer 21 connected to the other end of the transformer 20, an input terminal 23 connected to the other end of the transformer 20 via a DC blocking capacitor 22, and a DC blocking capacitor 24, 25 connected to both ends of the transformer 21, respectively. The output terminal 26 and 27 are connected together, and an impedance matching resistor 28 is connected between the output terminals 26 and 27. In the above configuration, the impedance of 75Ω on the input terminal 23 side is converted to 37.5Ω by the transformer 20, and then to 75Ω by the transformer 21, so that the impedance of the input terminal 23 is
The television signal given to the transformer 20
After impedance matching is performed, the signal is divided into two parts by a transformer 21 and sent out from output terminals 26 and 27. Therefore, by connecting each television receiver to the output terminals 26 and 27, it becomes possible to listen to the same television receivers. This type of distributor has excellent electrical characteristics such as a small number of circuit components, low distribution loss, large isolation between the output terminals 26 and 27, and a voltage standing wave ratio close to 1.

However, conventional television signal distributors of this type have been designed to distribute television signals in the VHF and UHF bands of 76 to 770 MHz, so they have been designed to distribute television signals in the VHF and UHF bands of 76 to 770 MHz, so they have been designed to distribute television signals in the VHF and UHF bands from 76 to 770 MHz. When dealing with ~1335MHz signals or 10~76MHz signals for two-way transmission with broadcasting stations by installing a transmitter in each home's television receiver, the frequency band is as wide as 10~1335MHz. ,
When these signals are distributed using a conventional distributor, there is a drawback that the electrical characteristics deteriorate at high frequencies. The reason for this is that the impedance matching transformer 20 does not perform constant impedance matching over a wide frequency band, so the output impedance changes and the voltage standing wave ratio worsens, and the input impedance of the distribution transformer 21 also changes. Therefore, the output terminals 26, 2
It is conceivable that the isolation between 7 and 7 may deteriorate. Furthermore, when used in a wide band, distribution loss increases at high frequencies. The reason for this is that the output impedance of the impedance matching transformer 20 and the input impedance of the distribution transformer 21 are low at 37.5Ω, so in order to make this part on a dielectric substrate such as a printed circuit board to match the impedance, the wire must be thick. You need to do it, but transformer 2
The wires used for the transformers 20 and 21 cannot be made very thick, so in most cases a capacitor is inserted in the wire between the transformers 20 and 21 to correct the impedance. However, when the frequency becomes high, the distribution loss increases due to the correction capacitor.

Further, as a circuit for the distributors 9 and 10 shown in FIG. 1, a circuit as shown in FIG. 3 is also known. This distribution circuit includes a distribution transformer 30, an input terminal 32 connected to the midpoint of the distribution transformer 30 via a DC blocking capacitor 31, and an impedance matching transformer 33 connected between both ends of the distribution transformer 30 and the ground. , 34, output terminals 37 and 38 connected to the respective midpoints via respective DC cutoff capacitors 35 and 36, and an impedance matching resistor 39 connected in parallel to the distribution transformer 30. . Here, capacitors 31, 3
5 and 36 are provided because the current-carrying coils L ₁ and L ₂ are connected in parallel between the input terminal 32 and the output terminals 37 and 38 as shown by the two-dot chain line in FIG. When transmitting a low frequency power supply current superimposed on a high frequency signal, transformers 30, 33, 34
This is to prevent the flow of power supply current to. Note that the power coils L ₁ and L ₂ are not provided, the capacitor 31 is omitted, and the capacitors 35 and 36 are connected in series between the transformers 33 and 34 and the ground, respectively, and the midpoint of the transformers 33 and 34 is connected to the ground. The output terminals 37 and 38 may be connected to each other so that the power supply current is superimposed on the high frequency signal and transmitted.

In the configuration shown in Figure 3, the impedance of 75Ω on the input terminal 32 side is doubled by the transformer 30.
The input terminal 3
The television signal given to the transformer 30
After the signal is divided into two parts by the transformer 33 and 34, the signal is impedance matched and sent out from the output terminals 37 and 38. This type of distribution circuit has the disadvantage that the number of transformers is increased by one compared to the one in Figure 2, but the impedance at both ends of the transformer 30 is 150Ω, which is twice the coaxial cable connected to the input terminal 32. , the impedance on the output side of the transformer 20 shown in FIG. 2 is four times as large as 37.5Ω, and there is an advantage that impedance matching between input and output can be easily achieved over a wide frequency band. The impedance of the coaxial cable connected to the input terminal 32 is made to be constant, for example 75Ω, so if you use the distribution circuit shown in Figure 3, you can use a wider frequency range than the one shown in Figure 2. It is thought that the electrical characteristics will be improved over the band. Moreover,
The impedance value of each conductor connected to both ends of the distribution transformer 30 varies depending on the length and arrangement of the conductor, as well as the capacity and installation condition of circuit components such as the transformers 30, 33, and 34.
It was difficult to make the impedance value of each conducting wire equal to 150Ω, and therefore it was not possible to obtain desired electrical characteristics.

[Purpose of invention]

The present invention was made in order to eliminate the drawbacks of the prior art as described above, and provides a television that can easily and accurately improve electrical characteristics over a wide frequency band using a distribution circuit as shown in Figure 3. The purpose of the present invention is to provide a digital signal splitter.

[Summary of the idea]

In order to achieve this purpose, the present invention extracts the middle point of the distribution transformer and uses it as an input terminal, and
Both ends of the distribution transformer are connected to the first and second impedance matching transformers via the first and second impedance matching transformers, respectively.
In a television signal distributor in which these output terminals are mounted on the surface of a rectangular dielectric substrate having a conductive layer grounded on the back surface and housed in a conductive case, an abbreviation of the surface of the dielectric substrate is used. The input terminal and the distribution transformer are placed in the center, and conductive wires with a round cross section wound around the distribution transformer are pulled out from both ends of the distribution transformer by approximately the same length in different directions, and are placed on the surface of the dielectric substrate. arranged at a predetermined height and connected to the first and second output terminals via the first and second impedance matching transformers,
The height of the center line of the conducting wire drawn out from both ends of the distribution transformer is adjusted based on the back surface of the dielectric substrate, so that the conducting wire has a predetermined impedance value.

[Example of idea]

Embodiments of the present invention will be described below with reference to the drawings.

FIGS. 4 1 and 2 show the internal wiring structure of the television signal distributor according to this embodiment, and FIG. 1 shows a front perspective view of the distribution circuit shown in FIG. FIG. 2 is a rear perspective view showing a pattern of conductive connection points provided on the back surface of the substrate. In addition, in FIG. 4 1, the resistor 39 in FIG.
is omitted to take advantage of the dielectric loss of the core constituting the transformer 30, and in FIG. 4, the portion other than the island portion A to be soldered is a ground pattern B. In FIG. 4, 40 is a rectangular dielectric substrate having a grounded conductive layer (earth pattern B) on the back surface, and this substrate 40 is preferably small enough to satisfy the condition of width a<length b. It is formed into a vertically long shape. An input terminal 32 is provided at the side end of the substrate 40 at approximately the center.
Capacitor 31 and transformer 30 in the horizontal direction of 2
will be placed. Further, output terminals 37 and 38 are provided at positions approximately equidistant from the center of the substrate 40 in the longitudinal direction, and transformers 33 and 34 and capacitors 35 and 36 are sequentially arranged in the vertical direction with the transformer 30 at the center.

As shown in FIG. 5, the distribution transformer 30 is composed of a cylindrical ferromagnetic core 30a and a conductor wire 30b with a round cross section wound around the core. The same length is drawn out in the vertical direction and connected to impedance matching transformers 33 and 34, respectively. The specific structure of these transformers 30, 33, and 34 is, for example, as follows.

Distribution transformer 30 Manufacturer name: Nippon Ferrite Co., Ltd. (NFK) Material of magnetic core 30a: T314 Length L of magnetic core 30a: 6.0 mm Diameter of magnetic core 30a D ₁ ; 3.5 mm Inner diameter of magnetic core 30 a D ₂ ; 1.0 mm Polyurethane Wire diameter of coated conducting wire 30b;
0.29mm impedance matching transformer 33, 34 Manufacturer name: Nippon Ferrite Co., Ltd. (NFK) Material of magnetic cores 33a, 34a: QM051 Length l of magnetic cores 33a, 34a; 3.0mm Long hole d ₁ of magnetic cores 33a, 34a; 5.0mm Short diameter d ₂ of magnetic cores 33a, 34a; 3.0mm Windings 33b, 34b coated with polyurethane
Wire diameter: 0.18 mm Here, as shown in FIG. 6, the dielectric substrate 40
The impedance Z ₀ when the strip-shaped polyurethane-covered conductive wire 30b' is stretched over it is expressed by the following equation.

Z ₀ =377/(w/h)・√[H(1.735εr ^-0.0724 )
・ (w/h) ^-0.836 ] In addition, w: Width of conductor 30b' h: Thickness of dielectric substrate 40 (however, copper foil B
thickness ≪h).

εr: Dielectric constant of the dielectric substrate 40 Then, if paper-based phenolic resin is used for the dielectric substrate 40, and εr = 4.8, w = 0.3 mm, and h = 1.6 mm, the impedance of the conductor 30b' is Z ₀ from the above equation. is about
It becomes 130Ω. Here, by appropriately selecting the conducting wire 30b having a circular cross section to be wound around the distribution transformer 30, it is possible to improve the electrical characteristics over a wide frequency band. Here, since the size of the conducting wire 30b cannot be made too thin due to the winding work of the conducting wire 30b, the distribution transformer 30
When the wire diameter of the conducting wire 30b is set to 0.29 mm as described above and the wire is arranged as shown in FIG. 6, the impedance of the conducting wire 30b is approximately 150 Ω from experimental results.
In this way, by pulling out the conductive wires 30b from both ends of the distribution transformer 30 in opposite directions to approximately the same length and running them over the board 40, it is possible to easily and precisely conduct the wires 30b.
Since a 150Ω line can be obtained, it is easy to balance the output levels of the output terminals 37 and 38, and it is also possible to reduce mismatched portions.
Therefore, it is possible to reduce distribution loss and improve standing wave ratio and isolation over a wide frequency band.

Fig. 7 1, 2, 3, and 4 are diagrams showing the experimental results of each electrical characteristic with respect to frequency using the distribution circuits of Fig. 2 and Fig. 4; Fig. 1 shows the distribution loss characteristic; is the standing wave ratio characteristic of the input terminal, Figure 3 is the standing wave ratio characteristic of the output terminal, and Figure 4 is the isolation characteristic between the output terminals. and the solid curve is the fourth circuit characteristic.
The circuit characteristics shown in the figure are shown. As is clear from Fig. 7, the circuit shown in Fig. 4 has particularly good electrical characteristics at high frequencies, and therefore a distribution circuit with excellent electrical characteristics over a wide frequency band can be easily and accurately obtained. be able to. In addition,
The width a of the dielectric substrate 40 in FIG. 4 only needs to have a length equal to the size of the input capacitor 31 and the diameter of the transformer 30, and therefore, the width a can be made small. Furthermore, transformer 33,3
4 and capacitors 35 and 36 are arranged in the longitudinal direction on both sides of the transformer 30, so they are connected to the substrate 4.
By arranging it close to the center position of 0, it is possible to reduce the length b of the substrate 40,
Moreover, both ends of the transformer 30 and each output terminal 37, 3
8, it becomes easy to adjust the impedance to a constant level over a wide band.

Figure 8 1 and 2 show the distribution circuit of Figure 4 in case 50.
Figure 1 shows the rear view,
2 is a perspective view seen from the front. The case 50 includes a dielectric substrate 4 on which electrical circuit components are mounted.
0, and mounting members 52 and 53 extending from both ends of the case body 51. Here, the ground pattern of the dielectric substrate 40 is connected and fixed to the inner surface of the case body 51 by soldering or the like. Output terminal plugs 54 and 55 are provided on the front of the case body 51, and an ohm band 56 for the input terminal is provided on the same side. The input terminal 32 in FIG. 4 is connected to the ohm band 56, and the output terminals 37 and 38 are connected to the plugs 54 and 55, respectively, by soldering or the like. Further, the mounting members 52, 53 are provided with mounting screws 57, 58, etc. In order to fix such a case 50 in a box 60 embedded in a wall surface as shown in FIG. It is pulled into the box 60 through the insertion hole 61, pulled out of the box 60, and fixed to the ohm band 56 of the case 50. Then, push the case 50 together with the coaxial cable 70 into the box 60, screw the screw into the screw hole 57 of the case 50 to fix the case 50 inside the box 60, and then insert the flash plate 62 into the front opening of the box 60. The flash plate 62 is fixed by inserting screws into the screw holes 58, and the parts above the plugs 54 and 55 are shielded. Here, if the dielectric substrate 40 is made small and vertically long as described above, the case body 51 can also be made small and vertically long, and therefore the installation work inside the box 60 can be easily performed. The advantage is that it can be done.

Note that, as shown in FIG. 1, the number of turnouts 3 to 8 installed in building A is usually greater than the number of distributors 9 and 10, so the shape of the case 50 and dielectric substrate 40 is designed to be suitable for turnouts. Just make one and use it as a distributor. That is, the difference between the branchers 3 to 8 and the distributors 9 and 10 is that the former has a function of sending out an input signal as an output signal at a predetermined level, whereas the latter has such a function. The point is that it has not been done. Therefore, in the case of a branch, a plug for outputting the output signal is provided on the side surface of the case 50, and this plug is connected to the output terminal provided in the output terminal notch 80 (see FIG. 8) of the dielectric substrate 40. Connected. Therefore, when wiring a distribution circuit using such a branch printed circuit board 40 (see FIG. 8), an output terminal notch 80 is provided at the side end position of the dielectric substrate 40 facing the input terminal 32. Therefore, the usable space in the width direction of the printed circuit board 40 is limited by the space of this notch 80, but even in such a case, the fourth
The wiring structure as shown in the figure can be effectively applied, and therefore the cases 50 can be standardized.

Further, the distribution circuit shown in FIG. 4 may be housed in a vertically elongated case 90 as shown in FIG. 10. This case 9
0 has an opening on the top surface and an input connector seat 9 on the side thereof.
1 and output connector seats 92 and 93, and after inserting the distribution circuit mounted on the dielectric substrate 40 from the top opening, the top opening is closed with a lid body and then installed on the wall of the room, etc. Secure with screws, etc. In such a case 90, due to installation work, the output connector seat 92
Although the distance between and 93 cannot be made very small, it is possible to reduce the size in the width direction by making it into a vertically elongated shape. Therefore, if the distribution circuit shown in FIG. 4 is housed in such a case 90, it is necessary to make the dielectric substrate 40 vertically elongated and small. However, even if the dielectric substrate 40 is made small in this way, the iso We can provide a distributor with good distribution.

11 and 2 show another method of connecting the distribution transformer 30 and the capacitor 31 in FIGS. 4 1 and 2. FIG. 11 shows details of the wiring diagram shown in FIG. 4, in which conducting wires 30b drawn out from both ends of the magnetic core 30a are connected to the transformer 31 via the island portion A. If the length of the lead-out portion C of the conductor 30b from both ends of the magnetic core 30a to the island portion A is long in this way, when a thin conductor 30b is used, the inductive component of the lead-out portion C becomes large, and high-frequency signals are It may become difficult to pass through and the electrical characteristics may deteriorate. Therefore, as shown in FIG. 11 and 2, the shape of the island portion A is made approximately T-shaped, and the length of the drawn-out portion C is reduced by connecting the conducting wires 30b drawn out from both ends of the magnetic core 30a to the island portion A located directly below. By making it shorter, it is possible to eliminate the adverse effects caused by the thinness of the conducting wire 30b.

In the above embodiment, even if the capacitor 31 and resistor 39 shown in FIG. It can be measured.

[Effect of idea]

As explained above, according to the television signal distributor according to the present invention, the input terminal and the distribution transformer are arranged approximately at the center of the surface of the dielectric substrate, and the input terminals and the distribution transformer are arranged approximately at the same length from the distribution transformer in different directions. Connect the first and second output terminals to the drawn out conductor via the first and second impedance matching transformers,
Since the height of the center line of the conductor is adjusted to give the conductor a predetermined impedance value, it is easy to balance the output level between the output terminals, thus reducing distribution loss and reducing standing waves over a wide range of frequencies. It is possible to measure improvements in ratio and isolation. Moreover, since the dielectric substrate on which the electric circuit components are mounted can be made vertically long and compact, the case in which it is housed can be made compact, and therefore the installation work can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an example of the wiring structure of a branch and a distributor, FIGS. 2 and 3 are circuit diagrams of a conventional distributor, and FIG. 4 1 and 2 are distribution diagrams according to an embodiment of the present invention. Figure 5 is an enlarged view of the main parts of Figure 4, Figure 6 is a diagram for explaining the circuit characteristics of Figure 4, Figure 7 is 1, 2, 3, 4. 8 is a diagram showing the experimental results of the distribution circuit shown in FIGS. 2 and 4, FIGS. 8 1 and 2 are diagrams showing the circuit of FIG. 4 housed in a case, and FIG. Explanatory diagram for installing the case No. 2 into the box, No. 10
The figure shows the circuit in Figure 4 housed in a case different from Figures 1 and 2 in Figure 8, and Figure 11 1 and 2 show the circuit in Figure 4.
It is a figure which shows the other connection method of the distribution transformer in a figure. 30...Distribution transformer, 30b...Conducting wire, 3
2... Input terminal, 33, 34... Impedance matching transformer, 37, 38... Output terminal, 40
...Dielectric substrate, 50, 90... Case, 60...
...Botx.

Claims (1)

[Claims for Utility Model Registration] 1. The middle point of the distribution transformer is drawn out and used as an input terminal, and both ends of the distribution transformer are connected to the first and second impedance matching transformers via the first and second impedance matching transformers. In a television signal distributor in which output terminals are mounted on the surface of a rectangular dielectric substrate having a conductive layer grounded on the back side and housed in a conductive case, approximately the center of the surface of the dielectric substrate is provided. The input terminal and the distribution transformer are placed on the surface of the dielectric substrate, and conductive wires with a round cross section wound around the distribution transformer are pulled out from both ends of the distribution transformer by approximately the same length in different directions, and are placed at a predetermined position on the surface of the dielectric substrate. from both ends of the distribution transformer with the back surface of the dielectric substrate as a reference. A television signal distributor characterized in that the conductor wire is adjusted to have a predetermined impedance value by adjusting the height of the center line of the lead wire. 2. A television signal distributor according to claim (1) of the utility model registration, characterized in that the case has a vertically elongated shape, and the dielectric substrate has a substantially rectangular shape in accordance with the shape of the case. Distributor. 3. In the distributor according to claim (1) of the utility model registration, the distribution transformer is connected by connecting the middle point of the distribution transformer and the input terminal using the conductive layer of the dielectric substrate. A television signal distributor characterized in that the lead-out length of the conductor wire is shortened.