The Application Of OQPSK Synchronizatipn Algorithm In IEEE802.15.4

With the prosperity of the rapid development of information technology andcommunication technology, human society has entered a new information age.A morecomplete development of fast communication systems has become increasinglyimportant.Offset quadrature phase shift keying (OQPSK: offset quadrature phase shiftkeying) modulation technique is the spectral characteristics of the constant envelopemodulation techniques, and has a very high spectral efficiency and powerutilization.Environment suitable for a data transmission system, the practical applicationof a wide range of applications in the fields of satellite communication and mobilecommunication.OQPSK modulation and demodulation techniques widely used in thehigh-speed wireless data transmission system, in particular satellite communicationsystems and terrestrial mobile communication systems, are increasingly meaningfulresearch directions.OQPSK modulation and demodulation techniques, has important theoretical and practical value.The paper first describes the background and current situation of OQPSKmodulation and demodulation technology applications, leads to the in-depth study ofQPSK modulation and demodulation technology principle on the basis ofOQPSK.OQPSK QPSK improvements, it is the phase relationship is the same as withQPSK, the symbol is divided into the same direction and the quadraturetwo-way.OQPSK the inphase and quadrature two path code flow in the time shifted halfa symbol period, and therefore does not appear two road symbol polarity flipsimultaneously.Then analyzed OQPSK modulation and demodulation principle to doin-depth research and its key technologies, including digital downconversion shapingfilter.OQPSK modulation and demodulation system simulation platform is built inMATLAB.Second in the spread spectrum communication applications, there isproposed an improved joint estimation of the carrier frequency and phase of theprogram based on the IEEE802.15.4new modulation and demodulation algorithm.Thecore idea is the use of the maximum likelihood estimation method, the complexity ofthe algorithm is not high, it is estimated that the error is smaller estimated multipleaccess interference generated by high-power users is particularly accurate, thuseffectively eliminating multiple small power users interference, so that the overall errorrate dropped. The oretical analysis and simulation results show that the performance of this algorithm is superior to the traditional single-user detector performance and betterresistance to the "proximity effect".And accordingly designed a simple and efficientmodulation and demodulation circuit.Hardware simulation show that the demodulatorcomplexity about5.1db upgrade similar to the traditional non-coherent demodulationperformance.Finally, the hardware implementation of the program.