JPS6230531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a circuit for a branching switch 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 the communication line for the carrier intercom. For example, using the wiring diagram of the wired communication equipment shown in FIG.
A transport type intercom 5 is connected to each of c and 3d. In such a wiring state, the television signal received by the receiving antenna 1 is distributed to the distribution terminals 2a and 2b of the distributor 2, and the television signal is distributed to the distribution terminals 2a and 2b of the distributor 3.
The signals are supplied to television receivers 4 connected to terminals a and 3b, respectively. On the other hand, communication signals between the carrier intercoms go back and forth between the branch terminals 3c and 3d of the branch 3. However, as is well known, in the branching device used for communal television reception, as will be explained with reference to FIG. Since the signal passing from the branch terminal 7 to the branch terminal 7 has a directionality such that it is attenuated by 30 dB, each call signal going back and forth between the branch terminals 3c and 3d of the branch terminal 3 is connected to the branch terminal 3 in the above example. If you use
The sum of 10dB and 30dB is 40dB, which means that the signal from the other party's carrier intercom is expressed as a ratio.
The problem is that the clarity of communication will be significantly reduced, meaning that the number will be reduced to 1/100.

SUMMARY OF THE INVENTION An object of the present invention is to provide a branch circuit suitable for use when a common television reception facility is shared as a communication line for a carrier type intercom.

Hereinafter, the present invention will be explained with reference to the drawings.

FIG. 3 shows the circuit of the branching switch of the present invention.
9 is an input terminal, 10 is an output terminal, 11 is a branch terminal T1 is a coupling transformer, L1 is a primary winding, L2 is a secondary winding, and these are wound around a ferrite magnetic core in a sufficiently coupled state. and the primary winding L
The a side of 1 is connected to the center conductor 9' of the input terminal 9, and the b side is connected to the center conductor 10' of the output terminal 10. The c side of the secondary winding L2 is a parallel resonant circuit 12
The d side is connected to the center conductor 11' of the branch terminal 11.
connected to. T2 is a matching transformer, with L3 as a primary winding and L4 as a secondary winding, which are wound around a ferrite core with sufficient coupling to each other, and the f side of the primary winding L3 and the secondary winding L4 The g sides are connected to each other, the intermediate tap h is taken out, the e side of the primary winding L3 is connected to the center conductor 9' of the input terminal 9, and the intermediate tap h is connected to the center conductor 1 of the branch terminal 11.
1'. The i side of the secondary winding L4 has a resistance of 1
Grounded via 3. 12 is a parallel resonant circuit composed of a capacitor 14 and a coil 15, one end of which is grounded, and the other end connected to the c side of the secondary winding L2 of the coupling transformer T1.

Next, regarding the branch circuit with the above configuration, for example, when obtaining a branch circuit when the impedance of input terminal 9, output terminal 10, and branch terminal 11 is 75 Ω each, coupling loss is 10 dB, and the signal frequency of the carrier intercom is 20 MHz. The constants of each part will be explained.

The coupling transformer T1 uses a ferrite magnetic core,
In addition, the primary winding L1 and the secondary winding L2 are connected at a turns ratio of 1:
The matching transformer T2 uses a ferrite magnetic core, and a primary winding L3 and a secondary winding L4 are wound thereon at a turns ratio of 3:1. Resistor 13 is 120Ω, capacitor 14 of parallel resonant circuit 12 is 20PF, coil 1
5 is 3 μH.

Figure 4 shows a characteristic diagram of the branch circuit configured with the above numerical values, where A is the insertion loss and the output terminal 1 when a signal is input from the input terminal 9.
The amount of signal loss at 0, B is the coupling loss at input terminal 9
C indicates the amount of signal loss at the branch terminal 11 when a signal is input from the output terminal 10, and C represents the amount of signal loss at the branch terminal 11 when a signal is input from the output terminal 10. As shown in the figure, in the TV frequency band 90-222MHz VHF band, coupling loss is 10 dB, reverse coupling loss is 30-35 dB, insertion loss is 1 dB,
In the UHF band from 470 to 770 MHz, the characteristics are 11 dB of coupling loss, 20 to 25 dB of reverse coupling loss, and 1.5 dB of insertion loss. It was done.

In addition, when two of the above branch switches are connected in series and a carrier intercom is connected to each branch terminal,
Attenuation of signals between intercoms is reverse coupling loss
The result is 23 dB, which is the sum of 12 dB and 11 dB of coupling loss, and the signal from the other party's carrier intercom is attenuated by about 1/14th.

FIG. 5 shows a circuit in which a well-known two-way divider 16 is connected to the branch terminal 11 of the branch of the present invention, so that the television receiver 4 and the transport type intercom 5 can be connected independently.

FIG. 6 is a wiring diagram of a joint reception facility using a branch circuit using the branch circuit shown in FIG. 5. One of the two branch terminals 11 is connected to the antenna terminal of the television receiver 4, and the other It is connected to the transmission and reception terminals of the transport type intercom 5 via power supply lines 17, respectively.

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. Furthermore, since the loss in communication lines between devices such as carrier intercoms is significantly reduced, communication with extremely high clarity can be achieved, and important communication contents can be accurately conveyed. Can be done.

[Brief explanation of the drawing]

Fig. 1 is a wiring diagram of wired communication equipment, Fig. 2 is a diagram showing the symbol mark of a branch, Fig. 3 is a circuit diagram of the present invention, Fig. 4 is a characteristic diagram of the branch circuit of the present invention, Fig. 5 is a different circuit diagram of the present invention, FIG. 6 is a wiring diagram of a joint reception facility for a branch using the branch circuit of FIG. 5, and FIG. 7 is a usage state of the branch using the branch circuit of FIG. Figure shown. 9...Input terminal, 10...Output terminal, 11...
Branch terminal, T1...coupling transformer, T2...matching transformer, 12...parallel resonant circuit, 13...resistance.

Claims (1)

[Claims] 1 Connect one end of the primary winding of the coupling transformer to the input terminal and the other end to the output terminal, connect one end of the secondary winding to one end of the parallel resonant circuit, and connect the other end of the parallel resonant circuit to Ground and connect the above coupling transformer 2
The other end of the next winding is connected to the branch terminal, one end of the primary winding of the matching transformer and one end of the secondary winding are connected to the branch terminal as an intermediate tap, and the primary winding of the matching transformer is connected to the branch terminal. A branching switch characterized in that the other end of the secondary winding is connected to an input terminal, the other end of the secondary winding is connected to one end of a resistor, and the other end of the resistor is grounded.