JPS637482B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a branching device used in wired communication equipment that allows for example UHF and VHF band television signals to coexist with mutual communication signals such as carrier intercom signals.

It is conceivable to share common television reception equipment as a communication line such as a carrier-type intercom. For example, using the wiring diagram of wired communication equipment shown in FIG. 1, a television receiver 3 is connected to branch terminals 2a and 2c of a branch 2, and
A transport type intercom 4 is connected to each of the terminals 2d. In such a wiring state, the receiving antenna 1
The TV signal received at the branch terminal 2 of the branch 2
The signals are supplied to the television receivers 3 connected to terminals a and 2c, respectively. On the other hand, communication signals between the carrier intercoms go back and forth between the branch terminals 2b and 2d of the branching device 2. However, as is well known, the branching device used for joint TV reception is designed to prevent spurious signals leaking from the local oscillator of the TV receiver from flowing back from the branch terminal and causing beat interference to other TV receivers. The branching characteristics have directionality. To explain this using Figure 2, the signal branched from the input terminal 5 to the branch terminal 7 will be attenuated by 10 dB in the case of a splitter with a coupling loss of 10 dB and a reverse coupling loss of 30 dB, Since the signal passing from the terminal 6 to the branch terminal 7 is attenuated by 30 dB, each bidirectional signal going back and forth between the branch terminals 2b and 2d of the branch 2 has an attenuation of 10 dB when the branch in the above example is used as the branch 2. and 30dB added
40 dB, which means that the signal from the other party's carrier intercom is reduced by a factor of 100, which poses the problem of significantly reducing the clarity of communication.

The present invention is suitable for use when common television reception equipment is shared as a communication line of a specific frequency band such as a carrier intercom, and only signals of a specific frequency have bidirectionality, and television signals have directional properties. The object of the present invention is to provide a turnout having the following features.

FIG. 3 shows a branching device of the present invention, which is constructed with a turns ratio of 1:n, 8 is an input terminal, 9 is an output terminal, 10 is a branch terminal, and 11 is used as a first branch element. In the transformer, L1 is the primary winding, L
2 is a secondary winding, and these windings are sufficiently connected to each other and wound around, for example, a cylindrical ferrite core to form a closed magnetic path. and 1
The a side of the secondary winding L1 is connected to the input terminal 8, the b side is connected to the output terminal 9, the d side of the secondary winding L2 is grounded, and the c side is the specific frequency bidirectional generation element 1.
Connected to the h side of 6. 12 is an autotransformer used as a second branching element, L3 is a primary winding, L4 is a secondary winding, and these are sufficiently coupled to each other to form a closed magnetic path in, for example, a cylindrical ferrite core. It is made up of 1
The winding end side of the secondary winding L3 and the winding start side of the secondary winding L4 are connected, and the intermediate tap f is taken out.
The e side of the secondary winding L4 is connected to the input terminal 8, and the intermediate tap f is connected to the branch terminal 10. The g side of the primary winding L3 is connected to the j side of the resistance element 13, and the other end k side is grounded. Furthermore, resistance element 13
The resistor 14 is used to create the directionality of the branch, and the well-known resistor 14 shown in FIG. 4 is used, and as shown in FIG. A capacitor 15 having an extremely small reactance at high frequencies may be connected in series for the purpose of blocking high frequencies and passing only high frequencies. Reference numeral 16 denotes a specific frequency bidirectional generation element, which gives the splitter bidirectional characteristics at a specific frequency. For example, a parallel resonant circuit composed of a capacitor 17 and a coil 18 is used, and its h side is connected to the c side of the secondary winding L2 of the transformer 11, and its i side is connected to the branch terminal 10.
connected to. As shown in FIG. 7, the specific frequency bidirectionality generating element 16 is a parallel circuit of a capacitor 17 and a coil 18, and is designed to block direct current or commercial power frequency transformation and pass only high frequencies. A configuration in which a capacitor 19 having an extremely small reactance at high frequencies is connected in series may also be used.

Next, regarding the branch circuit with the above configuration, we will explain the constants of each part when the impedance of the input terminal 8, output terminal 9, and branch terminal 10 is 75 Ω each, the coupling loss is 10 dB, and the signal frequency of the carrier intercom is 20 MHz. do.

The transformer 11 uses a cylindrical ferrite core, and has a primary winding L1 and a secondary winding L2 connected to it.
A cylindrical ferrite core is used for the autotransformer 12, and a primary winding L3 and a secondary winding L4 are wound thereon at a turns ratio of 1:3. The resistance value of the resistance element 13 is 100 to 130Ω, the capacitor 17 of the specific frequency bidirectional generation element 16 is 20PF, and the coil 18 is
Set to 3μH.

Figure 8 shows a characteristic diagram of the branching circuit configured with the above numerical values, where A is the insertion loss, the amount of signal loss at the output terminal 9 when the signal is input from the input terminal 8, and B is the coupling C indicates the amount of signal loss at the branch terminal 10 when a signal is input from the input terminal 8 due to loss, and C represents the amount of signal loss at the branch terminal 10 when a signal is input from the output terminal 9 due to reverse coupling loss. As shown in the figure, the coupling loss is 10 dB in the VHF band of 90 to 222 MHz in the TV frequency band.
Reverse coupling loss 30~35dB, insertion loss 1dB, 470~
In the 770MHz UHF band, coupling loss is 11 dB, reverse coupling loss is 20 to 25 dB, insertion loss is 1.5 dB, and coupling loss is at 20 MHz, the frequency used by carrier intercoms.
Characteristics of 11 dB, reverse coupling loss of 12 dB, and insertion loss of 1.2 dB were obtained. In addition, when two of the above-mentioned branchers are connected and a carrier type intercom is connected to each branch terminal, the signal attenuation between the intercoms will be 23 dB, which is the sum of the reverse coupling loss of 12 dB and the coupling loss of 11 dB. The signal from the intercom is
Expressed as a ratio, the attenuation is approximately 1/14th.

As described above, in the present invention, TV broadcast signals have directional properties, and signals in arbitrarily selected and determined frequency bands such as carrier intercoms have bidirectional properties. This prevents spurious signals leaking from the TV receiver's local oscillator from flowing backwards through the branch terminals and into the later stages of the receiving equipment, and also prevents negative effects on the image quality of the TV receiver connected to the branch terminals of the front branch. Moreover, losses in communication lines between devices such as carrier-type intercoms are significantly reduced, making it possible to communicate with extremely high clarity and accurately convey important communication contents. be able to.

[Brief explanation of the drawing]

Figure 1 is a wiring diagram of wired communication equipment, Figure 2 is a diagram showing the symbol mark of a switch, Figure 3 is a diagram showing an embodiment of the switch of the present invention, and Figure 4 is an example of a resistance element. Figure 5 is a diagram of different resistance elements, Figure 6 is a diagram showing different resistance elements.
7 is a diagram showing an example of a specific frequency bidirectionality generating element, FIG. 7 is a diagram showing different specific frequency bidirectionality generating elements, and FIG. 8 is a characteristic diagram of the branching device shown in FIG. 3. 8... Input terminal, 9... Output terminal, 10... Branch terminal, 11... Transformer, 12... Auto transformer, 13... Resistance element, 16... Specific frequency bidirectional generation element.

Claims (1)

[Claims] 1 Connect one end of the primary winding of the transformer used as the first branch element to the input terminal, the other end to the output terminal, and connect one end of the secondary winding to the specific frequency bidirectional generation element. The other end of the specific frequency bidirectional generation element is connected to a branch terminal, and the other end of the secondary winding of the transformer is grounded, and the other end of the specific frequency bidirectional generation element is connected to the autotransformer used as the second branch element. The intermediate tap to which one end of the primary winding and one end of the secondary winding are connected is connected to the branch terminal,
The other end of the secondary winding of the autotransformer is connected to the input terminal, the other end of the primary winding is connected to one end of a resistance element for creating directionality of the turnout, and the other end of the resistance element is connected to the input terminal. A turnout characterized by being grounded.