The Design Of Digital Modulation And Demodulation Teaching Experiment System Based On VC

Modulation and demodulation technology is a key technology in communication system. The effect of modulation and demodulation has direct impact on the performance of the communication system. Developing a digital modulation and demodulation experiment system is practicallly significant. The experimental teaching system can be used for both undergraduate and postgraduate courses teaching, and token to be as an assistant tool to design communication system for professionals.In this thesis, the design and scheme of the digital modulation system is given after the in-depth studying of the digital modulation and demodulation technologies and related theory.The system includes five kinds of digital modulation and demodulation experiments:QAM, OFDM, ASK, PSK and FSK. Based on the operating principle of modem technology, the modem structure and the function of each module is designed and the specific test content and test questions is given; the interface of each modular’s interface of inputting and adjusting parameters is designed in order to achieve the related modem; the waveform and spectrum of each point is given in order to comprehend the working principle and analyze modulation performance; the testing and experimental test interface is designed, achieving the function of submitting, updating and querying test online; the function of querying and analyzing test results is achieved in order to find the weak links and improve experimental teaching.In the thesis, the human computer interface of the digital modulation and demodulation system is designed by Visual C++6.0 software. The system establish and connect to the database using ADO technology, completing the data including experimental test and student achievement storage and query function; Establishing connection with VC by using Matlab engine, the system complete the data transmission between each point’s signal waveform and spectrum and VC interface. After the completion of the simulation system design, the varied function of the whole simulation system is tested and analyzed.The results show that:The system has the characteristics of design and integrated experiment system and the design of the varied modulation of the whole system is proved to be right. Students can not only complete the design of varied digital modem by designing and adjusting system parameters according to design requirement, but also observe the waveform and spectrum of each point in order to understand the working principle and analyze modulation performance. Besides, they can test online partly and completely. Teachers can submit and update test; they can also query test results and statistical analysis of test results.