Scheme of an fmbroadcast coverage system for a submarine tunnel

Scheme of an fmbroadcast coverage system for a submarine tunnel
(Beijing hengxingketong Technology Development Co., http://www.bjhxkt.com 010-82565576)
Necessity of constructing an fmbroadcast coverage system for Submarine Tunnel

As of 2017, China's total highway mileage reached nearly 0.14 million kilometers, and there were a large number of Highway Bridge tunnels in mountainous areas in the central and western regions. In some large and medium-sized cities, many urban tunnels were built to solve the traffic congestion problem, long Tunnels such as cross-sea tunnel and cross-river tunnel appear. The local traffic broadcast FM signal coverage is basically achieved along the expressway, but the signal coverage in the tunnel is not included in the design of highway tunnel and urban tunnel construction, most drivers have the habit of driving and listening to the FM sound machine. When a vehicle enters the tunnel, the signal is interrupted, affecting the integrity of the program. After an accident occurs in the tunnel, it may take several minutes or minutes for the traffic police and tunnel management personnel to arrive at the scene of the accident. If a serious accident occurs in the tunnel, a fire may occur, therefore, after an accident occurs in the tunnel, an emergency evacuation broadcast system is urgently needed. FMFM broadcast in the expressway tunnel is a good emergency broadcast. Drivers can obtain evacuation and emergency command information through the radio, this service provides emergency incident command and handling to guide drivers to avoid risks. Therefore, whether in terms of security or service to the work and life of the majority of passengers and passengers, it is necessary and important to add an emergency broadcast system in the tunnel and enhance radio open-circuit frequency modulation broadcast signal coverage.

Working principle of fmbroadcast coverage system for Submarine Tunnel

The tunnel FM signal coverage system uses the "FM receiving antenna + Optical Fiber remote transfer + FM direct release + leakage cable" to overwrite the tunnel FM signal. A dedicated eight-wood frequency modulation receiving antenna installed outside the tunnel hole receives the air FM broadcast signal and transmits it to the two-way tunnel after frequency selection and photoelectric conversion, the optical fiber FM direct station is used to enlarge the frequency modulation signal, and the leaked cables are routed to the tunnel to complete the tunnel frequency modulation coverage. When an emergency occurs in a tunnel, you can enable the "group carrier" emergency broadcast host to enable wireless coverage of emergency broadcast signals in the-MHz full band. Drivers only need to keep the radio on, you can receive emergency broadcast information to minimize the loss of personnel and property.

Iii. Scheme Design of emergency channel FM signal coverage system
3.1 FM signal reception

An eight-tree oriented receiving antenna is set up in a relatively open and high-altitude location outside the tunnel to receive open-circuit FM broadcast signals at-MHz. After the received FM broadcast signal is amplified by a high-gain antenna amplifier and filtered by a band-pass filter, the RF optical transmitter is used for electro-optic conversion and sent to the tunnel management center data center through optical cables.

3.2 mixed frequency selection and Signal Transmission

After the open-circuit FM broadcast signal sent to the data center is converted to an optical receiver, two modes can be used for frequency selection: first, a digital frequency converter is used to directly select the frequency points to be covered; the second is to send the signal to a multi-channel FM modem, demodulated the frequency points to be covered into standard audio signals, and then sent to the frequency modulation modulated by the frequency modulation broadcast program to the original frequency, the hybrid output is reused by the RF mixer. The frequency selection signal is converted by the optical near-end electromechanical light and sent to the tunnel through a single-mode optical cable.

3.3 full-band emergency broadcast for group carrier hosts

Microphone, MP3 files, and local audio are connected to the audio console and output to the group carrier host. In case of emergency, you can enable the Group carrier host for emergency signal coverage. The Group carrier host uses full-band and multi-carrier full coverage technologies. At the same time, in the 87.5-200 MHz full-band, the host outputs 103/206 sub-carriers at the same time at a frequency interval of kHz/kHz, enable 87.5-MHz full-band communication of emergency broadcast signals, when all FM broadcast programs in the frequency band are switched to emergency broadcast content.

3.4 FMFM broadcast coverage Signal Transmission

The transmission medium from the main control room to the signal coverage site is a single-mode optical fiber cable. FMFM broadcast signals are transmitted over the optical fiber cable to avoid excessive signal attenuation and prevent interference during signal transmission, and the attenuation difference in the inter-frequency transmission reaches the minimum, so as to meet the needs of the FM coverage system.

3.5 FM signal wireless coverage

The fiber-optic FM direct playback station receives signals from the data center. After photoelectric conversion, the station carries out two-channel output for amplification and overwrites the data through the exposed cable along the tunnel. Depending on the different leaked cable diameter, generally, one fiber-optic FM direct station is used to cover 1-km of the single hole. Tunnel shells with low bending and short distance are covered by Broadband Antennas.

Iv. successful case of fmbroadcast coverage system of hengxingketong undersea Expressway Tunnel
? Fmbroadcast coverage system of Hangzhou City Expressway Tunnel
? Fmbroadcast coverage system of Guizhou renhuai Moutai Expressway Tunnel
? Broadcast and coverage system of Yangtze River Crossing Tunnel in Wuhan, Hubei Province
? Fmbroadcast coverage system of cangling Expressway Tunnel of Zhejiang Provincial Expressway
? Fmbroadcast coverage system of Qingdao Jiaozhou Bay undersea Expressway Tunnel
? Qingdao Jiaozhou Bay Tunnel cluster wireless communication coverage system
? Fmbroadcast coverage system of Hengqin expressway tunnel of the University of Macau
FM coverage system for underground parking lots in Lenovo headquarters (Beijing)

Scheme of an fmbroadcast coverage system for a submarine tunnel