He Design Of A New Generation Of GPS-B Code Decoding Timing System

In electric power system, high precision clock is very important for the running state information acquisition unit during operation. Microcomputer relay protection device, dispatching automation system, fault recorder, event sequence recording device, remote control device, computer data exchange network and lightning location system equipment have a high requirement for timing accuracy. Operating parameters of these systems will be real-time recorded and stored in order to get the trend curve (including real-time curve and history curve).By analyzing these curves; we could sort the accident sequence, analyze causes, and then decrease accidents as well as improve the stability of system equipment.There are currently5timing modes in the word, which are shortwave time service, long wave radio, GPS, IRIG-B code timing service and network time. GPS and IRIG-B code timing service are two widely used timing modes in practice. And thus they have become the mainstream of timing mode at power system.In this thesis, based on the timing needs in the actual power system, I design a new type of multi service system whose module can accept GPS satellite signal and IRIG-B signal in the same time. This module could track GPS satellite acquisition time and accurate location information. It could receive IRIG-B signal time as well. After analyzing, information could be output by CAN and serial isolation interface. The two signals standby for each other which could satisfy various needs of the environment. Because the system module is designed on single chip, tit has high reliability, fast response, low cost, and relatively strong practical significance.According to the characteristics of the GPS satellite signals and the IRIG-B signals respectively, we first present the realization principles and signal demodulation method in detail. Then, we further propose a new method to solve the problem about coexistence of two kinds of signals. This method makes use of the characteristics of two kinds of signal acquisition and signal processing respectively by different functional areas at the same microcontroller, which ensure the system more integrated, more simple and reliable. The method is realized by software, so that the implementation cost was reduced greatly. GPS time signals, from the GPS receiver by satellite antenna, are sent out by RS-232communication protocol, The GPS information could be received by a pin receives using SCM serial and be analyzed to get the timing information by a single chip computer analysis. IRIG-B time format codes come from the standard IRIG-B code clock source. IRIG-B format time clock source codes are transmitted by RS-422communication protocol. Because the IRIG-B is a series of10ms width pulses which are low frequency, it can be acquitted by the SCM input capture function. Through analyzing the pulses, the microcontroller could give out the time information, which is output by CAN, RS-232, or RS-485t meets the needs of most system equipment demand.The time code decoding technology we present in this thesis is simple, low cost and easy operation. It also has a good promotions value. We think it has certain reference values on designing other time system.