Higher Order Modulation Signal Generator Design And Implementation

Signal generator is an important part of the design, simulation and electromagnetic environment simulation in communication system and a basic component in communication and communication countermeasure system, which is widely used in the fields of communication, radar, measurement, control, and teaching. However, there are some problems in the traditional signal generator such as low output frequency, low transmission rate and hardware problems such as large scale and not easy extension. In order to solve these problems, this paper in-depth study and do the following work:1) In order to solve the problem of low output frequency, limited the modulation function, poor extensible of the present digital signal generator, this paper put forward a kind solution of high order modulation signal generator, which adapts the idea of software radio to improve the extensibility and flexibility of the hardware platform; Through the DSP processor to improve data transmission rate and signal modulation ability; Use frequency converter to guarantee the output frequency.2)To study the thought of software radio, digital modulation theory, the frequency conversion, high efficiency digital filter theory, and MATLAB simulation, that is provided the necessary foundation for the actual development of frequency conversion processing on baseband signal processing.3) For defects of single DSP system, single FPGA system and the DSP+FPGA system, a higher order modulation signal generator design is proposed,which based on the software radio thought and adapted DSP processor as the core that combined with CPLD and frequency converter. The higher order modulation signal generator hardware design is designed with DSP as the core of the baseband signal processing、AD9857 as the core of the frequency conversion module and CPLD as the core control module. At the same time, for each module circuit and the interface circuit between module, the detailed design and analysis.has carried on.4) Higher-order modulation signal generator for the software design, the baseband signal processing for program design and simulation; Analyzed on a serial port communication mode between the frequency conversion chip AD9857 and DSP processor, and designed for it; It is studied in parallel port communication mode and the way of DSP external interrupt initialization, and designed for the parallel program; designed for the DSP external memory interface and read or write of FLASH program.5) Build the system test platform.By analyzing the test result of CCS3.3 software and the oscilloscope physical test results of oscilloscope observation, the data shows that the higher order modulation signal generator can produce 64QAM signals and 64ASK signal, which is to the expected design goal.