The Research On Applying Virtual Instrument Technology To Measure And Monitor Low-frequency Time-codes Time Service Signal

Low-frequency time-codes time service is recommended by ITU-R in middle or low precision time service systems. At present, the measuring method and instrumentation which is noticed in ITU-R new questions influencing the application of low-frequency time-codes time service system severely. It is very important to develop appropriate instrumentation to measure the transmitted signal in research and applications.Several formats of low-frequency time-codes signal were introduced, including DCF77, JJY and BPC. Based on the signal characteristic, the definition of signal field strength is given. Furthermore, the arithmetic to measure field strength and carrier phase is discussed and simulated by Matlab. The simulation figures that the arithmetic works very well.Virtual instruments technology, combined the computer technology and traditional testing technology, is the future of the modern testing system and is very befitting to be applied in measuring and monitoring low-frequency time-code time service signal. The portable BPC measuring system and monitoring system with software LabVIEW and DAQ (data acquisition) cards are discussed. The hardware composition and software structure are presented.With the developed instrumentation, the interference in receiving low-frequency time-codes signal is studied. There is some narrow band interference in the received signal which will severely damage the application. The experiments indicate that the interference can be cancelled by adaptive trap filter very well.Another important part is to release the monitoring result on the Internet. After compared the four methods used in virtual instruments, the result releases on the web by remote panel and datasocket technology.