JPH0535940B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a coaxial cable network having a superimposed transmission function of high and low frequencies.

3. Prior Art FIG. 3 is a block diagram showing an example of a conventional coaxial cable network, in which 31 is a coaxial cable, which is connected to a television 34 via a termination device 32 consisting of a 75Ω resistor and a branch 33 of the coaxial cable 31. The communication control device 35 is connected to an antenna 37 via a distributor 36 of the coaxial cable 31, and the signal received by the antenna 37 is passed through the distributor 33 to the coaxial cable and communicates with the high frequency signal received by the television 34. Low frequency waves used for communication by the control device 35 are transmitted via a coaxial cable.

In such a coaxial cable network, a terminating resistor that is suitable for high frequencies may not be suitable as a load resistor for a pulse transformer of a communication control device that uses low frequency signals. Therefore, when the signal waveform is unipolar, a configuration as shown in FIG. 4 has been used. This is pulse transformer 3
By using a flywheel diode 39 on the primary side of the pulse transformer 8, waveform undershoot can be suppressed without adding a load resistance to the pulse transformer 38.

In the case of a bipolar signal, if a similar form is taken, it will be as shown in Figure 5, and when receiving, either diode 4
1 turns on. Therefore, the input impedance seen from the information transmission medium to the pulse transformer 40 becomes small, and the amplitude of the pulse is attenuated.

Problems to be Solved by the Invention In such conventional coaxial cable networks, the terminating resistor may act as an unsuitable load resistor for the pulse transformer of the communication control device. In addition, there are three types of coaxial cable networks.
When the number of distributions increases to four, the load on the pulse transformer also changes because the number of terminating resistors increases. Therefore, the waveform sent out from the pulse transformer is also affected by the network configuration (distribution method).

The present invention has been made in view of these points, and has a simple configuration that allows a conventional terminating resistor to work for high frequencies, while providing an optimal load resistance for low frequencies that is unaffected by the network configuration. It is possible.

Means for Solving the Problems The present invention solves the above problems by connecting series circuits of capacitors and resistors to multiple terminals of a coaxial cable, and connecting series circuits of a choke coil and a resistor to any one location of the coaxial cable. Make the connection.

Effects The present invention has the above-described configuration, so that for communications using low frequencies, the series circuit of the chiyoke coil and the resistor acts as a load for the pulse transformer of the communication control device without being affected by the terminating resistor of the coaxial cable. For communication using frequency, only the terminating resistor is effective without being affected by the series circuit of the chiyoke coil and resistor.

Embodiment FIG. 1 is a block diagram of a communication control device showing an embodiment of the present invention. In FIG. 1, 1 is a coaxial cable, 2 is a termination device consisting of a series circuit of a capacitor 3 and a resistor 4 connected to the end of the coaxial cable 1, and 5 is a chain coil 6 connected to an arbitrary point on the coaxial cable 1. A pulse transformer load consisting of a series circuit of and a resistor 7, 8 is a coaxial cable 1
9 is a control device connected to a communication control device, 10 is a communication control device connected to
1 is a transmitting device, and 11 is a receiving device. 12 is a transistor for outputting a positive pulse to the coaxial cable 1, 13 is a transistor for outputting a negative pulse to the coaxial cable 1, and the collector of the transistor 12 is connected to one end of the primary winding of a pulse transformer 14 with a center tap. is connected to the other end, and the collector of the transistor 13 is connected to the other end, and a voltage of 5V is applied to the emitters of the transistors 12 and 13. A resistor 15 has one end connected to the output port A of the control device 9 and the other end connected to the base of the transistor 12. Similarly, resistance 1
6 has one end connected to the output port B of the control device 9, and the other end connected to the base of the transistor B. Therefore, when the output port connected to the resistor 15 of the control device 9 becomes low level, the transistor 1
2 is turned on, a current flows in the direction A through the primary winding of the pulse transformer 14, a pulse voltage is generated in the secondary winding, and a positive pulse signal can be transmitted to the coaxial cable 1. Similarly, when the output port connected to the resistor 16 of the control device 9 becomes low level, the transistor 13
is turned on, a current flows in the direction A in the primary winding of the pulse transformer 14, a pulse voltage is generated in the secondary winding, and a negative pulse signal can be transmitted to the coaxial cable 1. 17 and 18 are transistors whose collectors are connected to the input port of the emitter control device 9 and grounded. A resistor 19 has one end connected to the base of the transistor 17 and the other end connected to one end of the primary winding of the pulse transformer 14 . The other end of the pulse transformer 14 is connected to one end of a resistor 20, and the other end of the resistor 20 is connected to the base of a transistor 18. 21 is a pull-up resistor for setting the input port of the control device 9 to a high level. When the transistor 12 is turned on or when there is a positive pulse on the coaxial cable 1, a base current flows through the transistor 17, and the input port of the control device 9 becomes low level. In addition, the transistor 13
When turned on or when there is a negative pulse on the coaxial cable 1, the base current flows through the transistor 18, the input port of the control device 9 becomes low level, and the data on the coaxial cable 1 is monitored during transmission and is received. can do.

FIG. 2 is a block diagram of a coaxial cable network illustrating one embodiment of the present invention. 1 to 8 are the first
This is the same as 1 to 8 in the figure. 8' is communication control device 8
It is similar to , and is connected to the coaxial cable 1 via a branch 22 . 23 is connected to the coaxial cable 1 via the TV branch 22.
24 is a distributor 2 for transmitting the TV signal received by the antenna.
5 and coaxially.

First, when viewing the television 23 in this configuration, a television signal received from the antenna 24 is transmitted via the coaxial cable 1. In the case of such a high frequency, the coil 6 exhibits high impedance and does not work, so it is not affected by the load 5, and only the termination device 2 suitable for high frequency transmission works.

Next, communication between the communication control devices 8 and 8', that is, communication at a low frequency will be explained. Since the capacitor 3 does not conduct current for low frequencies, there is no effect on the pulse transformer by the terminating device 2, and if the wavelength of the low frequency is sufficiently long compared to the total length of the coaxial cable 1, the reflection of low frequencies can be ignored. By applying a load 5 suitable for communication using a low frequency, normal AMI communication can be performed. Similarly, even if the network configuration increases to three or four distributions, only the load 5 acts without being affected by the terminating resistor 4, and an optimal load can be applied to low frequencies.

In other words, it becomes possible to provide resistance suitable for both high and low frequencies, regardless of the form of the network.

In this embodiment, the load 5 is directly connected to the coaxial cable, but when a DC power source is superimposed on the coaxial cable, the load 5 is connected to the coaxial cable via a large capacity capacitor such as an electrolytic capacitor.

Effects of the Invention As described above, according to the present invention, highly accurate transmission of high and low frequencies can be realized with an extremely simple configuration without being affected by the network configuration, and is extremely useful in practice.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a communication control device for a home bus system according to an embodiment of the present invention, and FIG.
FIG. 3 is a block diagram of a coaxial cable network for a home bus system according to an embodiment of the present invention, FIG. 3 is a block diagram of a conventional coaxial cable network for a home bus system, and FIGS.
The figure is a block diagram of a conventional pulse transformer. 1... Coaxial cable, 2... Termination device, 3...
Capacitor, 4... Resistor, 5... Load, 6... Chiyoke coil, 7... Resistor, 8... Communication control device, 9... Control device, 10... Transmission device, 11...
...Receiving device.

Claims (1)

[Claims] 1 A communication control device that transmits and receives information packets via a coaxial cable, a pulse transformer whose primary side is connected to the communication control device and whose secondary side is connected to the coaxial cable, and which converts and amplifies the output signal of the communication control device. a transmitting device that controls a current in a primary coil of the pulse transformer; a receiving device that receives a transmission signal superimposed on the coaxial cable via the pulse transformer and converts it into a signal that can be input to the communication control device; a plurality of termination devices each consisting of a series circuit of a capacitor and a resistor connected to a plurality of ends of the coaxial cable; and a series circuit of a chiyoke coil and a resistor connected to an arbitrary point of the coaxial cable as a load of the pulse transformer. A coaxial cable network system comprising: