| The promotion and use of wireless shunting locomotive signaling and monitoring system(referred to as: STP system) in the railroad effectively prevent the shunting locomotive over the stop signal machine from happening squeezing accident, conflict accident and derailment accident caused by speeding, promote and improve the safety management level of the shunting operation, ease the pressure of the shunting staff.The characteristic of microwave communication transmission is that making use of the antenna in free space to achieve along the line of sight transmission. The assuming of free space propagation model ignores the influence on waves which is caused by the Earth’s surface, but in the actual ground communication, because of the presence of vegetation,buildings or mountains and other obstacles, they will destroy the line of sight path between the receiving and transmitting antennas. Through the wire ground reflection and diffraction analysis, a physical model of ground propagation is established. When the antenna distance from the transmitting to receiving is large, the received power is reached to a ten of fourth power attenuation with distance, and its loss is much faster than the free space. At the same time, the received power is independent of frequency, and related to the height of the transmitting antenna and receiving antenna. Because of the electric field of the receiver distributed in the adjacent Fresnel zone is reversed, its generating interference is destructive,rather than constructive. Therefore, we must make sure the first Fresnel zone of the direct wave is not blocked, the receiving point can receive the field strength of the free space. But the different shapes of obstacles(such as buildings, trees, etc.) often exist, and affect the transmission path, so the diffraction loss is greater than the free space loss.Combined with the new wireless shunting locomotive signal detection systems engineering design requirements, in accordance with the relevant provisions of engineering specifications, the thesis has performed a system design on the system components, functions,system equipment to transmit information and the principles laid. The system is divided into two parts: ground equipment and vehicle equipment, the two part of information exchange is completed by the means of wireless communication.Ground topography, station range, weather and so on are all factors that affect the field strength coverage of the system. Especially in the railway station of the mountain and hilly areas, building, tunnel, mountain, curve and other landforms can cause the wireless signal coverage to appear unstable weak field strength area, and even blind area. Through the main factors that affect the field strength coverage of the system are analyzed, we have proposed three schemes: the regulation of ground antenna, the addition based on repeater and the addition based on fiber optic repeater. Each scheme is introduced on applicable situation,theoretical analysis and link calculation, the three schemes are analyzed and compared instructions.Combined with the station environment and equipment condition of the Dazhou Railway Station, this thesis has conducted a preliminary design of the system engineering solutions and programs feasibility studies. From the communication quality, construction and maintenance, and project investment, the thesis make a comparison and analysis of the two schemes: the ground antenna adjustment and the additional repeater. According to the review comments of preliminary design solution of the Chengdu Railway Administration and the long-term development program of Dazhou Railway Station, we have optimized and improved the scheme, and finally formed a construction program. For installation and post repair and maintenance, ground hosts, electrical services maintenance terminal, vehicle service terminals, automotive and ground antennas host common symptoms may encounter,the thesis gives judgment and treatment method. |
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