Study On Key Technologies Of π/4-DQPSK Modulation And Demodulation Realized By FPGA

In recent years,software defined radio emerges as the times require along with the technique of digital signal processing growing up and the performance of digital processing instrument being consummate.It's based on the principles of modern communication with digital signal processing for core,and supported by the technique of micro-electronics.Its basic concept is making hardware as the platform,realizing the function of wireless communication system and personal communication system by software as much as possible.Software defined radio is called the third revolution in wireless communication field following digital communication and mobile communication,and it will influence the future deeply.The task of topic is realizingπ/4-DQPSK modulation and demodulation system from baseband to intermediate frequency by FPGA.π/4-DQPSK modulation is a linear narrowband technology,which possesses features of high spectrum utilization ratio, better spectrum speciality and stronger anti-fading performance.The modem method has been applied widely in mobile communication system,satellite communication system because of its excellences.Firstly,This thesis studies basic principle ofπ/4-DQPSK modulation part in modem system and makes solution to each module,emphasizes pulse shaping filter and DDS,emulates each key module in Matlab and presents the results.Secondly,the research studies basic principle ofπ/4-DQPSK demodulation part in modem system and makes solution to each module,emphasizes differential detection,DDC and bit synchronization,emulates each key module in Matlab and presents the results also.The next step is using Matlab to emulate the whole system and get the result.On this foundation,each module will be designed by VHDL(Very High Speed Integrated Circuit Hardware Description Language) in QuartusⅡ7.0 of Altera,and the accuracy of function will be proved through the emulation result.Next,design PCB from schematic Document to encapsulation,then to layout in Protel 99 SE.When finishing jointing, download the designed procedure to FPGA main chip.Finally,observing signal waveform,constellation diagram and eye diagram in oscillograph.This system signal source rate 100 kbps,modulated intermediate frequency 10 MHz.The accuracy of the system will be proved by test result.Theπ/4-DQPSK modulation and demodulation system from baseband to intermediate frequency has been realized.