Research Of Frequency Division Multiplexing By Cable Carrier Communication Technology Based On XCP

The eXpendable Current Profiler(XCP) is a measuring instrument which canobtain marine of environmental parameters quickly and cheaply.In recent years,suchequipment is widely used in marine natural disaster warning,environmental surveysand military applications.In strong support of Nation Plan Items of863, the NationalOcean Technology Center initiates a large-scale research projects of XCP system.The highlight of this paper is the collection of underwater data and thetransmission mode based FDM.During rotation of the vertical,XCP probe quickly getsthree types of information including temperature signal,electrode signal and coilsignal through the internal sensor. They are exteemely weak signal. Designing a signalconditioning circuit for filtering and amplifying weak signal so that it is notsubmerged by ocean noise. Furthermore, because the frequency signal is moresuitable than the voltage signal to be transmitted in o wired channel, using thevoltage-frequency converter, the analog signal is converted to a frequency signal,thethree signals are modulated in different frequency bands,and the three-way divisionmultiplexing singals are mixed to be an analog signal by FDM.Finally, the frequencydivision multiplexed signal is transmitted to the surface buoy.The first step is to conduct antomatic gain amplification in order to make thesignal amplitude maintain in a small range,then the-way FM signals are separated byactive filter and demodulated by the phase-locked frequency discriminator. Finally,thedemodulated signal is transmitted to the terminal on the helicopter by the wirelesstransmission.Because the wireless channel spectrum resource is scarce andinterference is more serious,the use of spread spectrum technology can not onlyimprove anti-jamming capability,but also play encryption protection for the collectedinformation on the underwater. The various parts modules of the system is emulatedand debugged by simulation software.Finally,the project are analyzed and summarized,and XCP system is proposed anew program in order to improve the efficiency of system and the quality of thecommunication.