JP4966230B2 - Underground shopping center AM broadcast retransmission system - Google Patents

Description

  The present invention relates to an AM broadcast re-transmission system for an underground shopping mall that can receive AM broadcasting in the underground shopping mall.

  In underground malls and tunnels, the AM broadcasting radio waves (560 kHz to 1700 kHz) are not well received, so the radio signal received by the ground receiving antenna is selected by the tuning circuit and retransmitted at the same frequency. An AM broadcast re-transmission in which a transmitter is provided and a radio wave transmission cable connected to the re-transmission device via a matching unit is provided on an underground shopping center or a ceiling in a tunnel to transmit radio waves for AM broadcasting from the radio wave transmission cable. A system is employed (see, for example, Patent Document 1). The radio wave transmission cable includes an induction cable that transmits radio waves by electromagnetic induction and a leaky coaxial cable that transmits radio waves from a coaxial cable. When a leaky coaxial cable is used, radio waves such as FM broadcast and TV (television) broadcast may be transmitted.

  On the other hand, in recent years, with the spread of Internet communication, terrestrial digital broadcasting, and the like, optical cables and coaxial cables for such communication and broadcasting have been arranged in underground malls. When using an optical cable, the optical fiber that forms the strand is made of a brittle material such as glass. Therefore, use an optical cable that has a suspension line coated with a coating material in parallel with the optical fiber. It is often installed on the ceiling or the like (see, for example, Patent Document 2).

JP-A-8-88609 (FIG. 9) Japanese Patent Laid-Open No. 10-68849 (FIGS. 2 and 4)

  Of the radio wave transmission cables used in the AM broadcast re-transmission system as described in Patent Document 1, the induction cable is less expensive than the leaky coaxial cable, but it is necessary to provide a guide wire for AM broadcasting alone. Therefore, in an underground mall where other cables for communication and broadcasting are arranged, there is a problem that the construction cost is excessive when considering the construction of the communication and broadcasting system for the entire underground mall.

  Accordingly, an object of the present invention is to enable an underground shopping center AM broadcast re-transmission system to be constructed at low cost while saving extra construction costs.

  In order to solve the above problems, the present invention selects a receiving antenna for receiving an AM broadcast radio wave transmitted on the ground and a received signal from the receiving antenna by a tuning circuit, and retransmits at the same frequency. Underground shopping area AM broadcast re-transmission system comprising: a re-transmission device that is connected to the re-transmission device via a matching unit; and a radio wave transmission cable that is disposed in an underground city and transmits a transmission signal from the re-transmission device as a radio wave. In the above, the radio wave transmission cable is an induction cable that transmits radio waves by electromagnetic induction, an optical cable having a conductive suspension line is disposed in the underground shopping area, and the conductive suspension line of this optical cable is connected to the A configuration is adopted in which the induction cable is connected to a re-transmission device and transmits the radio wave.

  That is, the radio wave transmission cable is an induction cable that transmits radio waves by electromagnetic induction, an optical cable having a conductive suspension line is disposed in the underground shopping area, and the conductive suspension line of this optical cable is connected to the re-transmission device via the matching unit. By connecting and using induction cables that transmit radio waves, optical cable suspension lines installed in underground shopping streets can be used for radio broadcasting cables for AM broadcasts, and the AM broadcast retransmission system for underground shopping streets can save extra construction costs. Made it possible to build at low cost. Since the optical signal transmitted through the optical cable is not affected by the radio wave (electromagnetic wave), the radio wave transmitted from the guide cable does not become a disturbance.

  In the underground broadcast AM broadcast re-transmission system of the present invention, the radio wave transmission cable is an induction cable that transmits radio waves by electromagnetic induction, an optical cable having a conductive suspension line is disposed in the underground shopping area, and the conductive suspension line of the optical cable is provided. Because it is an induction cable that connects to the re-transmission device via a matching unit and transmits radio waves, the optical cable suspension line installed in the underground shopping street is used for the AM radio wave transmission cable, saving extra construction costs And can be constructed at low cost.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, this underground city AM broadcast retransmission system receives an AM broadcast antenna transmitted from the ground and an AM reception antenna 1 connected by a coaxial cable 2. It consists of a re-transmission device 3 that selects a signal with a tuning circuit and re-transmits at the same frequency, and an induction cable 5 as a radio wave transmission cable connected to the re-transmission device 3 via a matching unit 4. The receiving antenna 1 is installed on the building roof adjacent to the underground shopping area, the retransmitting device 3 is installed in the receiving / transforming room in the building, and the two induction cables 5 connected to the matching unit 4 are at intervals of 30 cm or more. The terminal is connected to the terminal resistor 6.

  In this underground mall, a UHF receiving antenna 11a for digital terrestrial broadcasting and an FM receiving antenna 11b for FM broadcasting are also installed on the building roof so that they can receive digital terrestrial broadcasting and FM broadcasting, and are coaxial with these receiving antennas 11a and 11b. Retransmission devices 13a and 13b for digital terrestrial broadcasting and FM broadcasting connected by a cable 12 are installed in a receiving / transforming room in a building, and transmission signals from these retransmission devices 13a and 13b are optical modulation devices. 14 is converted into an optical signal and transmitted to an optical cable 15 disposed in an underground shopping center. The optical signal transmitted by the optical cable 15 is transmitted to the underground shopping street from the digital terrestrial broadcasting and FM broadcasting antennas 16a and 16b provided at various locations in the underground shopping street.

  As shown in FIG. 2A, the optical cable 15 is formed by covering a plurality of optical fibers 15a with a covering material 17 such as a resin, and in parallel with these optical fibers 15a, using a conductive metal wire. A suspension member 18 is covered with a covering material 17, and a tension member 19 that reinforces the optical fiber 15 a is also embedded in the covering material 17. The covering member 17 is provided with a neck portion 17a between the covering portions of the suspension wire 18 and the optical fiber 15a in order to make it easy to install with the suspension wire 18, and in order to make the optical cable 15 easily branched, the optical fiber 15a. A cut portion 17b is provided at the center of the covering portion.

  The optical cable 15 is installed on the ceiling of an underground shopping center with a suspension line 18, and a part of the optical cable 15 is installed in parallel at intervals of 30 cm or more as illustrated in FIG. Is connected to the matching unit 4 and is used as a guide cable 5 for transmitting a radio wave for AM broadcasting to an underground mall. Therefore, it is possible to construct an underground shopping center AM broadcast re-transmission system at low cost while saving extra construction costs. In the example shown in FIG. 2B, one optical cable 15 is a branch cable with a small number of optical fibers 15a.

  In the above-described embodiment, the optical cable is provided with a neck portion between the hanging portion and the coated portion of the optical fiber in the covering material. However, the optical cable may have a conductive hanging wire, and the covering material may have a neck. There may be no part.

  In the above-described embodiment, the suspension line of the optical cable for digital terrestrial broadcasting and FM broadcasting is used as the guide cable for AM broadcasting. However, the suspension line of another optical cable for the Internet or the like is used as the guidance cable. You can also.

System diagram showing an embodiment of an AM broadcast retransmission system for underground shopping centers 1 is a cross-sectional view showing the optical cable of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reception antenna 2 Coaxial cable 3 Retransmission apparatus 4 Matching device 5 Guidance cable 6 Termination resistor 11a, 11b Reception antenna 12 Coaxial cable 13a, 13b Retransmission apparatus 14 Optical modulation apparatus 15 Optical cable 15a Optical fiber 16a, 16b Antenna 17 Covering material 17a Neck part 17b Cut part 18 Hanging line 19 Tension member

Claims (1)

  Receiving antenna for receiving radio waves for AM broadcasting transmitted on the ground, a retransmitting device for selecting a received signal from the receiving antenna by a tuning circuit and retransmitting at the same frequency, and a matching unit for the retransmitting device In an underground city AM broadcast re-transmission system, which is connected to the base station and is disposed in an underground city and includes a radio wave transmission cable that transmits a transmission signal from a re-transmission device as a radio wave. The radio wave transmission cable transmits a radio wave by electromagnetic induction. An optical cable having a conductive suspension line is disposed in the underground shopping area, and the conductive suspension line of the optical cable is connected to the re-transmission device via the matching unit to transmit the radio wave. AM broadcast re-transmission system for underground shopping malls, characterized by cable.

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