JPH02274137A - Information transmission system for local area network - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an information transmission system for a local area network,
In particular, it relates to an information transmission system for a token passing bus type local area network.

[Prior art] The token passing bus is based on M A P (Hanuf
Acturing Autollation Prot
It is used as a lower layer of ocof). The configuration of the token passing bus type local area network is shown in FIG. 4, namely, trunk cable 1. Bidirectional amplifier 2. The main part is constituted by the headend remodulator 5, and the drop cable 3 coming out from each communication terminal 4 is connected to the trunk cable by a branch tap 6. Generally, coaxial cables are used for the trunk cable 1 and the drop cable 3, and the branch tap 6 makes contact with the center conductor by once cutting the trunk cable or by damaging the outer sheath.

[Problem to be solved by the invention] As mentioned above, in token passing bus type local area networks that do not use conventional coaxial cables as transmission paths, it is necessary to cut the main cable in order to accommodate branch taps. Otherwise, it is necessary to damage the outer cover, so it takes time and effort to add more communication terminals, and it is difficult to move them. In particular, frequent movement increases the number of points connected to the trunk cable and the number of damaged points, reducing the reliability of the trunk cable.

The second drawback is a major problem in factories where token passing bus type local area networks are expected to become widespread. Due to the shortened lifespan of the product, L
This is because production lines are often changed, which usually involves moving terminals. Furthermore, since there is a strong demand for the freedom of movement of communication terminals in offices, this drawback becomes a problem in that case as well.

The purpose of the present invention is to eliminate the drawbacks of the prior art mentioned above,
Provided is an information transmission method that allows communication terminals to be moved freely. It's in the second place.

[Means for solving the problem] The information transmission system of the present invention transmits electromagnetic waves as a trunk cable in a local area network having a communication protocol similar to the IEEE802.41-Kunpassing bus or similar communication protocol. Each terminal is connected by a branch tap with an antenna closely electromagnetically coupled to the cable, and a transmitter/receiver of each terminal performs wireless transmission between the antenna and the cable. It is from et al.

The configuration of the above-mentioned branch tap includes two types: a case where it is provided with two antennas for transmitting and a receiving antenna, and a case where it is provided with one antenna that is used for both transmitting and receiving 1S.

[Operation] The information transmission path is a tightly coupled wireless 1 transmission method that transmits and receives information signals wirelessly in a limited space, and the branch tap is a coupler that tightly electromagnetically couples the antenna to the main cable. Branch taps can be installed and moved without damaging cables.

[Example] Hereinafter, an example of the present invention will be described using FIGS. 1 to 3.

In FIG. 1, the trunk cable 1 uses a cable in which the periphery of the twisted pair wires is covered with a material that transmits electromagnetic waves.

6] is a casing of the branch tap 6, and a part of the gauging 61 is formed with a clamp portion for gripping the main cable 1. In this embodiment, as shown in FIG. 2, a C-shaped clamp lug 62 is provided on the -L portion of the gauging 61, and this C-shaped portion is detachably fitted into the main cable 1. However, the present invention is not limited to this. In any case, the branch tap 6 is thus mechanically fixed to the outside of the main cable 1 by the ramp portion 62, and does not damage the outer sheath of the main cable 1.

- In the gauging 61 described in F, a transmitting antenna 7 and a receiving antenna 8 for closely electromagnetically coupling the twisted pairs of the trunk cable 1 are arranged in parallel in the axial direction of the trunk cable 1 and connected to the trunk cable 1. It is fixed in position so that it does not move.

The branch tag 6 is connected to the information terminal 4 by a drop cable 3. To be precise, a hot wire transmitter 11 and a wireless receiver 12 are provided in the information terminal 4, and the transmitting antenna of the branch tap 6 is connected to the transmitting antenna of the branch tap 6 via the transmitting cable 9 and the receiving cable 10 passing through the drop cable 3. 7 and a receiving antenna 8.

The signal flow in this embodiment is as follows.

Frequency f1 transmitted from the transmitter 11 of a certain information terminal 4
The signal passes through the transmission cable 9 in the drop cable 3 and is electromagnetically coupled to the trunk cable 1 by the transmission antenna 7.Then, the signal is transmitted through the trunk cable 1, passes through the bidirectional amplifier 2, and is sent to the head end relay. The modulator 5 converts it into a signal of frequency f2. This time, the main cable 1 is propagated in the opposite direction, coupled to the receiving antennas 8 in all the branch taps 6, and the respective receiving cables 10
and reaches the receiver 12 of the information terminal 4.

In this way, a broadband information transmission path is formed between all the information terminals 4, and a token passing bus type local area network is realized.

Another embodiment of the present invention is shown in FIG. 3. In the branch tap 6 of this embodiment, a transmitting/receiving antenna 13 is fixed inside, and the drop cable 3 is a single core of a transmitting/receiving cable 14. A signal is transmitted to the transmitter 11 and receiver 13 by the duplexer 15 .

[Effects of the Invention] As described above, according to the present invention, it is possible to freely change the position of the branch tap without damaging the main cable, making it easy to add and relocate communication terminals, and to reduce production in factories. The degree of freedom in line layout can be greatly increased. Furthermore, even in an office or the like, the layout can be easily changed, portable information terminals can be moved freely, and it is possible to connect to a LAN from any location.

[Brief explanation of drawings]

FIG. 1 shows an example of the structure of a branch tap section and/or information terminal section applied to the present invention, FIG. 2 shows an example of the external appearance of a branch tag section, and FIG. FIG. 4 is a diagram showing an example of the configuration of a token passing bus type local area network. In the figure, 1 is a trunk cable, 2 is a bidirectional amplifier, 3 is a drop cable, 4 is an information terminal, 5 is a headend remodulator, 6 is a branch tap, 7 is a transmitting antenna, 8
1 is a receiving antenna, 9 is a transmitting cable, 10 is a receiving cable, 11 is a transmitter, 12 is a receiver, 13 is a transmitting/receiving antenna, 14 is a transmitting/receiving cable, and 15 is a duplexer. Patent applicant: Hitachi Cable Co., Ltd. Representative Patent Attorney Nobuo Kinutani

Claims (1)

[Claims] 1. In a local area network that has an IEEE 802.4 token passing bus or a communication protocol similar to this, a cable hidden by a material that transmits electromagnetic waves is used as the trunk cable, and the antenna is closely electromagnetically coupled to the cable. An information transmission system for a local area network, characterized in that each terminal is connected by a branch tap, and a transmitter/receiver of each terminal performs wireless transmission between the antenna and the cable.