Research On The All Digital Demodulatioin Of LRIG-B Code

The IRIG-B (B code) code is a international standard time code. IRIG-B code isselected as the standardized interface signal between timing equipment and user terminalsin the standardized timing system. Since user terminals get the standard information oftime and frequency via decoding the IRIG-B code, the precision timing system of B codedemodulation affects the one of timing system directly.The paper laid emphasis on the implement of the all digital demodulation of IRIG-Bcode. It was analyzed seriously that how to achieve the demodulation of IRIG-B (DC) codebased on FPGA, The entire demodulating plan and flaw are supplied, in which that how toextract the1PPS and information of time exactly is stressed. Finally, the results based onFPGA are supplied.On the analysis of the current methods, a new method of B (AC) code demodulation ispresented. In this method, that extracting the zero-crossing information of B (AC) code viaa all-digital Costas Loop is proposed for the first time. The use of Costas Loop replaces thetraditionally used zero detection circuits in which there are several problems includingpulse shaking and zero drifting. Moreover，the total program and structure based on FPGAof IRIG-B(AC) demodulation are provided. The application of the Costas Loop in B (AC)code demodulation is seriously analyzed and the Loop is simulated with differentparameter settings in MATLAB，and it is also implemented in FPGA. With analysis, it canbe concluded that the introducing of the Costas Loop will raise the precision of B (AC)code demodulation to1μs or even10-7s.