The Design And Realization Of Spread Spectrum Communication Experimental System

With the third generation mobile communication (3G) to become the leading modern communication, spread spectrum communication technology has been the most widely used in the field of mobile communications. According to different ways of spread spectrum, spread spectrum communication systems are divided into:direct sequence spread spectrum, frequency-hopping spread spectrum and hybrid spread spectrum. For the three modes of spread spectrum, designing an experimental spread spectrum communication system not only helps to study and master the spread spectrum communication theory, but also provides a comprehensive, design-based experiment platform for hardware and software.The spread spectrum communication experimental hardware platform and software system was designed by using the DDS chip AD9850 and SCM-51 as the core devices and based on learning and mastering the spread spectrum communication technology and deep studying on the control methods of DDS chip AD9850. The system can realize the signal transmissing of direct sequence spread spectrum, frequency hopping spread spectrum and DS/FH hybrid spread spectrum; can capture synchrony and despread the baseband direct sequence spread spectrum signal; can change the spread spectrum modes and experiment projects through software programming and switching; can change the spread spectrum technology parameters such as the spreading gain, the frequency hopping rate and the frequency hopping patterns.In this thesis, the whole system structure and technical parameters was designed according to the spread spectrum communication experiment teaching requirements and for developing the ability of engineering practice. On this base, each module circuit and PCB board was designed. Through installing and debugging the hardware circuit, programming and testing the software, the system test results and corresponding analysis were given. Some valuable conclusion was reached. The results show that:the direct sequence spread spectrum signals, frequency hopping signals and DS/FH hybrid spread spectrum signals are correct; the direct sequence spread spectrum signal can correctly be captured synchrony and despreaded; the spread spectrum technology parameters can be adjusted according to requirement. The experimental system was stable, easy to operate, meets the requirements of doing comprehensive and designed experiments.