GPS timing server (time synchronization server) network system used in airports
Anhui Beijing-Technology Original information
Abstract: The clock synchronization between multiple critical information systems Command and Control airport, departure system, broadcast and other flight information display, normal to the airport operational and security play an important role, this paper introduces the application and implementation of the system in Jinan airport.
Jinan Airport is an important air traffic hub in the province, it is a large modern airport. There are 94 digital clock at the airport, while the building of the departure system, flight information display multiple information systems, broadcast systems, Command and Control System, information security systems, building automation systems, security monitoring systems, parking management systems, call center systems, etc. systems that work together to connect with each other through the interface, time consistency is very important. The clock of each system by building a unified calibration clock synchronization system and lay a solid foundation for the system to work.
1, the application and the necessity of clock synchronization at the airport clock
time information of the communication device or various internet communication computer device (year, month, day, hour) based on the UTC (Coordinated Universal Time) time shift is limited within a sufficiently small range ( as 100ms), this synchronization process is called time synchronization.
Airport departure check-in systems that open and close at a specified time according to the time signal; FIDS displays flight information at a given time; broadcasting system broadcast a variety of information about visitors guide at the time of booking; building automation systems to control lighting, air conditioning based on the time open and close; command and Control systems rely on accurate time information of various departments to work together command of the airport; security monitoring system must be recorded each time the screen information; parking management systems rely on accurate time car parking fees; call center based on the time information to guide passengers opportunity; passengers and staff also need accurate time information.
Anhui Jing quasi-official micro-electronic technology - ahjzsz
An accurate clock system is an important basis for the airport each production system to function normally.
2, the system clock synchronization
2.1 Introduction
using the star structure, is provided an NTP server, receiving the standard time signal from the GPS is provided a high-precision master clock, the master clock signal received from the NTP time, and signal clock transfer subsystem clocks each pass, to provide a unified standard time of the intake / departure airport staff and passengers, while the master clock output (signal with millisecond) standard time signal to the network NTP time server, a network time server NTP through the computer network system, to provide a unified coordinated airport terminal and the business sector of the production run time signal, the timing of each electromechanical system devices synchronized with the system clock.
2.2 clock system consisting
clock system consists of GPS receiver, the central master clock, clocks, world clock, NTP server, and the transmission channel management control computer.
2.2.1 hardware schematic
of FIG. 1 is a schematic view of hardware components.
2.2.2 Detailed Description of Hardware
2.2.2.1 NTP (Network Time) server
network time server receives a GPS standard time information, standard time information and transmits this to the master clock. Standard network time server can provide time information to networked computers via Ethernet.
After the GPS antenna is properly installed and the standard time signal into the control center communication chamber, connected to the rear of the server network time, turn on the power switch, a network time server starts, after some time, the front panel display local standard time.
2.2.2.2 Center master clock
Master clock as a basis for the master clock of the whole clock system, it can receive standard time signal from a network time server, time accuracy of the calibration itself, and assigned to the respective sub-precision time signal clock. As the master clock is the central part of the whole time of the system, the stability of its work largely determines the reliability of the whole system, so to give full consideration to a combination of factors such as system implementation and system reliability features, its design-oriented, system unit arranged to pay machine, and the master can switch between manual or automatic pay machines. Master clock standard time signal via the standard RS422 interface receives transmission network time server. When the network time server is working properly, the time reference signal as a master clock; network time when the server fails, the master clock will use its high stability crystal oscillator as a time reference. Master clock by a standard RS422 interface to send the standard time signal is calibrated to their respective clocks, while receiving clocks loopback operation state information from, and the control clocks operating status information back to the monitoring terminal, the monitoring computer in display. Master clock connected via a standard RS232 interface and a computer monitor, to enable monitoring of the main device system clock, the time and the computer monitor.
When a power failure, the central master clock can still work 24 hours standby power support. When the central master clock can be synchronized with the school GPS, to keep pace. Within 96 hours blackout, when power is restored to automatically track, synchronized with the standard time.
When the central master clock can automatically school and GPS, to keep pace. Master clock synchronization error ≤10ms. Within 96 hours the power failure power is restored to the normal time can be automatically tracked.
2.2.2.3 monitoring terminal
is provided to control the clock terminal management system (i.e., computer monitor) in the center room, full Chinese display control interface, pull-down menu mode, having good interactive interface, and open its excellent expandability the number of clocks for display changes through a standard RS232 interface connected to the central master clock, with centralized maintenance functions and self-diagnostics, fault management may be carried out, the general performance management, configuration management and security management, the software interface that monitors FIG. 2 shown in FIG.
Monitor terminal comprises a monitoring computer, which is connected to the serial port via a cable directly to the central master clock, having a self-diagnostic function, fault management, performance management, configuration management and security management.
The system can be configured by monitoring terminal equipment capable of running real-time monitoring of the main system clock, the working state of the system, the fault status display can be performed system-wide clock monitoring point. Its ability to monitor and display the contents include: central master clock, the operating state of all clocks. When the system fails, the alarm monitoring software, indicating failure site.
2.2.2.4 clocks
clocks are connected via a standard RS422 interface to the central master clock. Under normal circumstances, the standard time signal reception center clocks transmitted from the master clock, the accuracy of the calibration itself, and may send back its own operating status information; when the standard time signal is not received, the sub-clock accuracy itself may take time. Terminal clocks used in all-digital slave clocks.
2.2.2.5 world clock
signal be calibrated, synchronized with the GPS time when the world clock by the time in different time zones 12 cities of the composition, each receiving a master clock digital clocks sent to the school. World clock independent of the crystal, if the master clock fails, world clock will work independently.
And when the world clock recovery function, world clock adjustment with a keyboard, a reset button and a power switch having a manual correction.
City Name world clock display is: Jinan, Tokyo, New York, Los Angeles, Paris, London, Berlin, Moscow, Sydney, Singapore, Cairo, New Delhi.
2.3 System Configuration and functional debug
2.3.1 GPS mounting
the antenna module to be mounted in a rugged, durable device housing. All elements of the antenna and the circuit modules are housed in a sealed antenna assembly. The main components of low profile microstrip antenna plug, ceramic RF filter (i.e. preselector) and a signal preamplifier. The antenna module is designed and tuned to receive the L1 wave effective partial signal transmitted by GPS satellites (nominal frequency of 1575.42MHz). Once the signal is received, the signal is amplified by the receiver into M12. A signal pre-amplification in the antenna module is an external power supply can be implemented by the receiver of M12. The antenna module of obtaining current 20MA nominally 5 volt DC power directly from the antenna connector M12 receiver.
Installation of the antenna module is connected to: a low profile antenna specially designed built-in antenna module, it is used in conjunction with the receiver M12. GPS signals received by the antenna is amplified in the antenna combination, then treated transmitted via a cable receiver module M12. The antenna is mounted in a plastic box to protect it from harsh environments.
Requirements for cable connectors: an antenna module forwards the received GPS signals and receive power supply (5Vdc, 20mA) from the receiver module via the same cable. We recommend using RG-58 coaxial cable connecting the antenna module and the receiver module. An antenna mounted on the module substrate as a radio frequency antenna circuit connected to the socket interface. Please note that the power cable loss at a frequency of 1575.42MHz (L1 band for GPS) is not more than 6dB. To meet the requirements 6dB loss, RG-58 cable length should be limited to less than 6 meters. Connecting ends of the cable between the antenna module and the receiver module must be at right angles to the plug-subminiature connector. Note that the RG-58 cable wire should be twisted wire. If provided with solid conductors, the installer is required to install the cable is bent in the antenna base, it must ensure that the operating state of holding the wire to be as good as the strand.
Set up an antenna must take full account of the local natural environment and electromagnetic environment, set up the choice of venue is particularly important. The antenna is generally placed in the open air, ice and sun, wind and rain, over time will inevitably fail, serious or even no signal, so the maintenance of the satellite antenna can not be ignored. For the GPS positioning performance at its best, when the antenna module is mounted, you must do the following four points:
the antenna plane same as the local horizontal plane;
antenna will face the sky, so that the head may look directly at all visible satellites. Regardless of the size of the antenna aperture size, should be set up in the local open as possible to the highest point of the open, away from the slopes, trees, tall buildings, towers, high voltage transmission lines and other blockage of the antenna beam. Should have sufficient field of view on the main beam direction of the antenna, the antenna should be as wide as possible in front of the viewing angle. General requirements for the antenna as a reference point, the highest point of the obstacle to an angle less than 3 degrees;
erected position of the antenna of the outlet should be avoided to reduce the wind load of the antenna. In thunderstorm areas, erect position of the antenna should avoid lightning-prone locations, and to take a variety of lightning protection measures;
Antenna module maintenance: After commissioning antenna mounting, upon reception of a determined satellite television signals, azimuth angle, elevation angle substantially fixed. To eliminate the effects of drift caused by the satellite can be measured based on the actual income effect, regular or irregular basis to fine-tune the antenna, so always in the best receiving state.
To prevent the antenna from lightning, the antenna should be mounted above the lightning rod, lightning protection grounding system must be carefully checked before the thunderstorm season is good arrival.
Installation 2.3.2 NTP server
should be installed in the engine room with the UPS system, and network system and the central master clock and use. Server network interface switches: RJ-45 used at both ends of the cable connector, the two connectors practice international standards EIA / TIA 568B, such a cable referred to as a parallel cable or a positive sequence line may NIC (Network Interface adapter) is connected and a switch or hub.
2.3.3 mounted master clock
should be installed in the engine room with the UPS system, and the NTP server and through the network cable, due to the master clock correction signal will be issued to the respective clocks, and therefore need to master clock signal is transmitted to line each sub-network is connected between the weak lines, when the clock correction signal into the distribution frame among weak points.
2.3.4 mounted clocks
installed in use position and is connected to the clock distribution frame through network sub weak.
2.3.5 Network Clock Set information source
disposed NTP server IP address of the network clock signal and the clock signal transmission protocol (SNTP protocol generally used). When each information system can use the clock information Netime, Sntp read clock software server's school, clock synchronization function.
3 summarizes
through the construction of Jinan clock synchronization system, so that the linkage between the various airport systems more smoothly, accurately and maximize the role of information systems.
