Talking about the application of different frequency relay in the weak field area of ​​railway wireless communication and the blind area of ​​tunnel

Talking about the application of different frequency relay in the weak field area of ​​railway wireless communication and the blind area of ​​tunnel


1. Introduction In the additional second line project between Xinlitun and Tongliao West on the Dazheng Line, there are three adjacent stations A, B, and C. Due to the addition of the second line, the B station is demolished, and the two stations are separated by 12.2km. The two stations of B and C are 13.4km apart, and there is a tunnel about 500m long on the up and down lines of station 1km from station A. Within 1km, there are large curves and cuts. Due to the demolition of the station platform of station B, the wireless telephone communication between the stations A and C has weak and blind areas. At present, the main ways to solve the weak field in the bright area are the deployment of relay stations and fiber optic repeaters. The former cost is lower, but because the space wave is not easy to control, the latter needs to lay fiber, which is suitable for long distance between stations, and the cost is relatively large.In order to solve the problem of weak and blind zone communication, according to the actual situation of this project, the different intervals in the design are different. Frequency relay, the use of leakless cable tunnel repeaters and special flat antennas in the tunnel. The equipment is selected from Huatong Space-Time Communication Technology Co., Ltd. products. The brief introduction of the project is as follows.

Second, the system composition The wireless train adjustment system is 450MHZ-C system, and the weak field different frequency relay frequency is 150MHZ.
(1) Weak field relay equipment in the bright section The weak field relay equipment in the bright section is composed of the first repeater type WJJ-11 and the tail type repeater type WJJ-12. The original station B at the edge of the zone communicates with the station platform and the locomotive in the weak field area through the relay and wireless forwarding functions of the head and tail repeaters. Station call locomotive: The station modulates 114.8HZ signaling of the calling locomotive to F1 transmission (F1 is 457.7MHZ), the first station receives F1 to demodulate 114.8HZ and then modulates to F2 transmission (F2 is 151.7MHZ.), And the tail station receives F2 Demodulate 114.8HZ and then modulate to F1 transmission. After receiving F1 demodulated 114.8HZ, the vehicle shows that it is called and sends 415HZ ring back signal. After corresponding operation, the two parties talk. Locomotive call station: For the above reverse flow, the call station signaling is 123HZ.
(2) Relay equipment in the blind zone in the tunnel WJS series relay is a special equipment for solving the communication in the tunnel without leakage cable.It consists of WJS-1 hole repeater, WJS-2 hole repeater, flat antenna, It consists of a power splitter connecting the repeater in the cave and the flat antenna, a SYV-50-9 RF cable, an intermediate frequency isolator connecting the two repeaters, and a YZW2X4.0 control cable. Among them, the control cable not only transmits the 220V AC power required by the repeater but also transmits the intermediate frequency 455KHZ containing call control signaling, and the two are separated by the intermediate frequency isolator. When the tunnel is shorter, no repeater can be installed in the hole, and more than 2 repeaters can be installed when the tunnel is long. One repeater can carry up to 5 flat antennas. The hole repeater is set in the hole relay room, the hole repeater is set in the car avoidance hole at an appropriate place in the tunnel, the flat antenna is mounted on the upper part of the hole wall, and the control cable, radio frequency cable and power splitter are set in On the wall of the cave. The communication process is as follows, the station calls the locomotive: the station modulates the 114.8HZ signaling of the calling locomotive to F1 transmission, and the hole repeater receives F1 to demodulate the intermediate frequency 455KHZ containing 114.8HZ signaling. Each repeater is modulated to F1 and transmitted to a flat antenna via a radio frequency cable and a power splitter. The locomotive receives F1 and demodulates 114.8HZ and then displays the called and sends a 415HZ ringback signal. After corresponding operation, the two parties talk. Locomotive call station: For the above reverse flow, the call station signaling is 123HZ. The communication between the station and the locomotive in the tunnel via the head and tail repeater is similar to the above

3. Equipment configuration Due to the dismantling of Station B, a new set of WJJ-12 tail platform repeaters was set up at Station B, and the first station repeater of WJJ-11 type was set up in Station C in addition to the original station platform. The original station platform of Station A remained unchanged A set of WJS-1 type repeater is set at the side entrance of station A of the upstream tunnel, which is responsible for the communication relay between station A platform and the locomotive in the upstream tunnel. Due to the short tunnel, there are no repeaters in the tunnel, only 3 flat antennas and 2 power splitters, and corresponding RF cables and relay cables; the equipment in the downlink tunnel tunnel is similar to the downlink tunnel , A set of WJS-1 type repeaters on the downstream side entrance, a set of tail station repeaters on station B, a set of first repeaters on station C, and a locomotive in the down tunnel passing through the hole repeaters and removing station B Communication between the newly-built tail station repeater, the first repeater of station C and the station platform of station C.

4. Frequency selection and field strength calculation According to TB / T3052-2002, the frequency of C system in the 450MHZ band is 457.700MHZ, and the inter-frequency relay frequency is 151.700MHZ. The median design value of the input level of the receiver of the locomotive in the 450MHZ band is 28dBμV (among them, the minimum available level of the radio station is 10dBμV, the fluctuation is 11.5dBμV, and the reserve is 6.5dBμV). Because the influence of the curvature of the earth is not significant in the field strength calculation range of wireless alignment, the plane earth formula is used to approximate the calculation.
1.450MHZ: Entry level of the receiving point: V input = P1-L1 + G1-L0-F + G2-L2. Where: P1 is the transmit power 5W (144dBμV); L1 is the transmit feeder loss 6dBμV; G1 is the transmit antenna gain 13dBμV; L0 is the free space transmission attenuation; F is the attenuation correction factor; G2 is the receive antenna gain 0dBμV; L2 is the receive feeder Loss is 3dBμV.
Free space transmission attenuation: L0 = 22 + 20lgd + 20lgf. In the formula: d is the distance between receiving and transmitting antennas (km); f is the carrier frequency (MHZ); L0 = 22 + 20lg13.4 + 20lg450 = 97.6dBμV.
Attenuation correction factor during plane ground propagation: F = 22 + 20lgh1.h2.f / d = 22 + 20lg25X4.8X
450/13400 = 34.1dBμV.
When the locomotive is 13.4km from the station: VIN = 144-6 + 13-97.6-34.1 + 0-3 = 16.3dBμ. V does not meet the requirements of 28dBμV, but can reach the working door opening level of the repeater.
2. The emission level of the flat antenna in the tunnel: (the output level of the repeater in the cave is 144dBμV [5W], the attenuation of the RF cable is 0.05dB / m, the spacing of the flat antenna is 160m, the gain is 1dBμV, and the attenuation of the main circuit of the power splitter is 3dB. The branch attenuation is adjustable from 3-25dB.) The farthest antenna emission level: P = 144-0.05 × 540-3 × 2 + 1 = 112dBμV, adjust the power splitter branch attenuation to 12dB, 24dB from far to near , Then the antenna emission level is 112dBμV. Because the propagation of radio waves in the tunnel is greatly affected by factors such as trains, tunnel wall structures, tunnel cross-sections and curves, the antenna spacing, power splitter branch attenuation and repeater output level should be adjusted according to the actual measured field strength. Strongly meet the requirements.

Fifth, equipment installation, the newly built operation room of station C, the station platform and the first repeater are set on the 25-meter iron tower, the antenna tower is set with a 10Ω lightning protection ground line, and the AC power required by the radio station is led by the communication machinery room; the use of station B is removed In the original 20-meter iron tower, the tail repeater was set in an unattended relay room, and the power supply was powered by solar energy. The repeater at the entrance of the tunnel is set in an unattended interval relay room, and the power supply is powered by solar energy. Interval relay rooms should pay special attention to the good settings of high-frequency surge arresters, system working ground wires and antenna tower lightning protection ground wires to ensure the safe operation of equipment. The radio frequency cable in the tunnel is hung on the hook on the upper part of the cave wall, and the flat antenna and power splitter are arranged on the top of the cave wall. The distance between the plate antennas is about 160m, and it is adjusted according to the actual field strength of the tunnel during construction. The main circuit attenuation of the power splitter is 3dB, and the branch circuit attenuation is adjustable from 3-25dB. The closer to the repeater, the greater the attenuation of the branch circuit, so that the output level of each antenna is basically the same.

6. Summary Resolving wireless weak fields such as mountain tunnels is a comprehensive project that requires the joint efforts of relevant railway departments and manufacturers. New weak field coverage equipment using new technologies reduces investment and improves the communication quality of weak field areas such as mountain tunnels. For the equipment that has been put into use, there should be improvement measures to solve the existing problems, tap the potential of the system, and meet the needs of rapid railway development.

Electric Grill

Electric Grill,Electric BBQ Grill,Portable Barbecue Grill,Electric Barbecue

Shaoxing Haoda Electrical Appliance Co.,Ltd , https://www.hotplates.nl

This entry was posted in on