JPS61220531A - Security communication system in tunnel - Google Patents

Abstract

PURPOSE:To attain inexpensive in-tunnel communication with excellent talking quality by using a parallel 2-wire in place of a leakage coaxial cable and adopting a single side band modulation system not susceptible to surrounding noises. CONSTITUTION:One end of a balanced 2-wire line 8 connects to a ground repeater station 9 and is relayed to a base station 10 by a wire or in radio as required, while the other end is terminated by a resistor RL. Further, portable inductive ratio telephone sets 11, 12 moved along the inductive line 8 are coupled to the inductive line 8 by an inductive magnetic field via an antenna coil mounted internally or externally. Thus, a noise current induced in the same direction to both a forward and a return path of the balanced 2-wire line is cancelled together. Moreover, the S/N is improved by adopting the single side band modulation system.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a communication system for ensuring mutual communication between the inside of an underground tunnel or a core and the surface.

(Prior art) In recent years, underground common ditches have been constructed and used for multiple purposes to lay and maintain high-voltage power transmission cables or other communication cables, etc. However, there are various types of work to be done within the Nirera Cave. Since this is dangerous, securing a secure means of communication is essential to ensure the safety of workers.

Various means of mutual communication inside the tunnel or between the inside of the tunnel and the ground have been devised, but it is extremely difficult to ensure secure communication inside the tunnel, especially in underground common ditches, etc. due to its topography.

Conventionally, as a method of expanding the communication between the inside of the cave and the ground and the communication distance within the cave, as shown in Fig. The portable wireless devices 3 and 4 communicate with each other by propagating radio waves, and communicate with the drone in the tunnel and the terrestrial mobile station 6 or base station 7 via the terrestrial relay station 5 connected to this leaky coaxial cable.
I was trying to communicate with.

Furthermore, in land mobile communications, the FM method is generally adopted, and even in the conventional tunnel private communication using the leaky coaxial cable mentioned above, the FM method is also used.
The M method was used.

(Problem to be solved by the invention) However, leaky coaxial cables are extremely expensive and have large transmission losses. To compensate for this, high frequency power amplifiers AMP are connected at predetermined intervals as shown in Figure 4. I needed to. For this reason, when installing over a long distance, not only a large number of AMPs are required and the equipment is complicated, but also the communication system equipment is extremely expensive.

Furthermore, if there is something in the tunnel that generates large electrical noise, such as a high-voltage power line, FM with a relatively wide band
A large amount of noise appeared in the demodulated output of the receiver, deteriorating call quality and further shortening the communication distance.

(Means for Solving the Problems) The present invention has been made in order to solve the various problems of the conventional tunnel communication. Single-sideband modulation method (SSB) that uses wires and is less susceptible to ambient noise
We provide an inductive communication method that employs

Moreover, we actually investigated the noise spectrum distribution inside the tunnel where the high-voltage power transmission line was laid, and in order to minimize the influence of these noises, we used a balanced two-wire guide line as the guide line, and the external environment of the guide line. Changes in impedance and transmission loss characteristics due to influences, etc. were investigated, and based on the results, an optimal intra-cave security communication system was created.

(Example) The present invention will be described in detail below based on illustrated embodiments.

FIG. 1 is a system diagram illustrating an embodiment of the present invention.

In the figure, reference numerals 8 and 8 indicate balanced two-line guide lines, which are laid parallel to each other on both sides of the upper part of the tunnel along the tunnel. One end of this balanced two-wire line jli'58.8 is connected to the terrestrial relay station 9 and relayed to the base station 1° by wire or wireless method as necessary, while the other end of the balanced two-wire line jli'58.8 is terminated with resistor RL.

Here, the balanced 2i-line line is one in which two lines are extended equally to the ground without being grounded, and their terminals are terminated with a required impedance.

Figures 11 and 12 show guide lines 8.8 installed inside the tunnel.
This is a portable induction radio telephone that moves along the guide lines 8, 8 and is coupled to the guide lines 8, 8 by an induced magnetic field via an antenna coil mounted internally or externally.

A specific example of the tunnel communication system configured as described above is as follows.

That is, the portable radios 11 and 12 have different transmitting and receiving frequencies, for example, a duplex system in which the transmitted wave is f1 and the received wave is fI, and the multiplied wave f1 of one portable radio is received by the ground relay station 9. The portable radios in the tunnel communicate with each other by converting and amplifying the wave f1 and sending it out again to the lines 8, 8, and receiving it by the other portable radio. Also, a terrestrial relay station 9 having a combination opposite to this frequency communicates directly with the portable radio device as necessary.

Furthermore, if the terrestrial relay station 9 is provided with a function as a wireless relay station, it is also possible to enable communication between other wireless base stations 13 or terrestrial mobile stations 14 and the portable wireless devices 11 and 12 inside the tunnel. .

Furthermore, the present invention will be explained in more detail by specifically showing each equipment of the above-mentioned communication system.

When examining the noise distribution in the tunnel where ultra-high voltage power transmission cables are laid, it is found that harmonic components of the power transmission frequency and various broadcast waves existing in high electric fields on the ground are mixed in. However, it is widely distributed in the range lQ kHz to 250 kHz, which is commonly used as a carrier wave for guided communications. In addition, the impedance characteristics and signal transmission loss of the balanced two-wire line depend on the frequency, the difference in the distance between the two lines, the distance between the two lines, the distance from the ground, and the ground height of the line, and the difference in the various conductive conductors for power transmission located near the structure. It varies greatly depending on the presence or absence of body substances and their quantity.

In implementing the present invention, taking these points into consideration, the frequency band used is set to 200 kHz to 500 kHz or more, and the upper limit is set to about 1.1 Ml(z).

Furthermore, in order to minimize the effects of various noises generated within the tunnel, it is preferable to lay the two-wire wire line so as to be in equilibrium with the source of the largest noise. In other words, the signal current that normally flows through a two-wire line whose one end is terminated with a resistor RL has opposite directions on the outbound and return routes.However, the noise generated in the tunnel is different between the outbound and return routes of the line. Since noise currents are induced in the same direction, by balancing the lines, such noises cancel each other out and their influence can be removed.

Next, when comparing the signal-to-noise ratio (S/N) of the received demodulated signal in each extraction modulation method, the single-sideband modulation method, the so-called SSB (Single 5ide Band) g modulation method, is advantageous. . That is, the S/N of each of the AM modulation method, 88B modulation method, and FM method is expressed by the following equation.

S/N(AH) -ka2A Ayu.・・・・・・(
1) s, /N (SS B) ”' 2 AC) 襦
・Book (2) S/N (FM) -3″'f>Gake.

......(3) However, 2B: Reception bandwidth (Hz) n: Noise power per unit band within the reception band Pe = A0/2: Carrier m Power ka; Modulation degree (AM and SSB) fd : Maximum frequency deviation in FM (Hz:) mf; Modulation index Comparing these respectively, S/'N (F% (AM) -12m2f """
(5) 8ha(-Bλ(SSB)-1,5m2f
−・・−・(6) However, in general, the occupied frequency band B(FM) in FM is B(FM) −2Cfd + fth ) −
-(7) Therefore, if S(FM)=S/N(SSB) is set in the above equation (6), m/ki082 is obtained.

That is, B(FM)-2(0,82J'a +fa)=3.6
47'a,, -(s).

Therefore, in order to make the S/N (FM) better than S (SSB), the occupied frequency band B (FM) of FM should be
．． The frequency must be 64 times or more, but this is extremely inconvenient in terms of effective frequency utilization and is not desirable when considering not only tunnel self-communication but also communication with the ground and multi-channelization.

Therefore, among the circular methods, the SSB modulation method is the most advantageous for the above-mentioned champion.

FIG. 2 is a block system diagram showing a specific embodiment of the present invention constructed in consideration of the above.

In the same figure, the balanced two-wire line 15.15 has a diameter of 1,6
(mn) of copper wire, the distance between them is 1 (m), and the maximum length is 3.5 km. The ground clearance (height from the floor of the tunnel) h is 2.5 m and the distance is at least 10 (pictures) from the ceiling. Also, the impedance of the line at this time is approximately 600
(Ω), so the terminating resistor tag at one end is set to 600Ω.

The transmission frequencies of the portable radios 16 and 17 are 1.0 to 1,1.
MHz, receiving frequency is 230-250 kHz,
The modulation method is SSB modulation, and its transmission frequency band B (SS
B) is 600 to 2600 Hz (6 dB reduction range), and the transmission power is P '' 13 B (mw). - The transmission and reception frequency of the Mannobujo fixed station 18 is opposite to that of the mobile radio 16.17, and the transmission output is 50Hz. (mvr).

In the tunnel self-communication system configured in this way, the antenna coils of the portable wireless devices 16 and 17 are shown in FIG.
) As shown in ), a high magnetic ferrite core (TDK, H5A) with external dimensions 8.5 x 16 x 60 (m).

When I made a call to terrestrial relay station 18 using a 0.4φ UFIW copper wire wound 100 times around l-60), the third
As shown in Figure (b), when the distance between the guide line and the antenna coil is 0.5 m, 8/N (SSB)
= 25dB or if the same distance is within 1m, S/N (S
A speech quality of SB) = 15 dB was obtained.

The embodiments of the tunnel self-communication system according to the present invention are as described above, but the present invention is not limited to these embodiments, and the present invention does not need to be limited to these embodiments. The frequency band to be used, the spacing between the tracks, etc. may be appropriately selected depending on the shape of the road, etc. Although we have omitted the details of the connection between the ground relay station and other ground stations, this can be connected to various existing security communication networks by wire or wirelessly.
It is clear that a selective call function added to the portable radio may be used to make a selective call call to a desired location.

There is no need to explain that these communication systems can be applied to either simplex or duplex communications, and that the present invention can also be used for remote control or remote monitoring of various devices installed inside a cave.

(Effects of the Invention) Since the present invention is constructed as described above, it is possible to improve communications within noisy underground common ditches, especially tunnels in which ultra-high pressure transmission cables are installed, or secure communications between these and above ground. It is extremely effective in realizing it very economically and efficiently.

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing the principle of the present invention, Fig. 2 is a system diagram showing a specific embodiment of the invention, and Fig. 3 is an implementation of the antenna coil of an induction radio used in implementing the invention. A dimensional drawing showing an example, and FIG. 4 is a system diagram showing a conventional tunnel private communication. 1...Cunnel, 2...Leaky coaxial cable, 3,4゜1
1, 12, 1.6 and 17... Induction radio, 5,
9 and 18...Terrestrial relay station, 6 and 14...Land mobile station, 7.10 and 13...Base station, 8.15...
Guide line, RL...Load resistance, AMP...Diameter. Application fee nil, 1.74 February Shinakyu, (i'□'
□ □I'.

Claims (2)

[Claims] (1) In a system in which a guide line is extended inside a tunnel such as an underground common ditch and communication within the tunnel is secured through this, the guide line is made of two balanced lines, and one end of the guide line is By terminating with a predetermined resistance and connecting the other end to a relay station installed on the ground, it is possible to connect portable induction radios that move within the tunnel along the guide line, or between these radios in the tunnel and a relay station on the ground. A security communication system within a tunnel, characterized in that communication is performed between terminal devices via a private branch exchange or the like. (2) The portable induction radio device adopts a duplex method, uses a carrier suppressed single sideband method (SSB) as a modulation method, and communicates within the tunnel through the ground relay station. The intra-cave security communication system according to claim 1, wherein the possible range of intra-cave communication is expanded by amplifying the signal propagating through the guide line at the ground relay station.