Virtual Radio Test System

Software radio is regarded as a great revolution to the structure of traditional radio communication system. Without the constraint of hardware structure, software radio is becoming the best way to solve the problems of co-operation among different modes and develop more services. It is of magnitude commercial and military value.Software radio system, with the core of general-purpose processor, is named "virtual radio" system because of its similar structure with virtual instrument. The development of virtual radio system is helpful to rapidly establishing a prototype system and accelerating the investigation of the structure of software radio system in depth. This is of much both theory and experience meaning. The paper focused on establishing virtual radio experiment system to implement narrow-band communication among different kinds of modes.The second chapter of this paper studied the structure frame of virtual radio experiment system. Under the direction of hardware/software co-design method, we implemented system modeling and partitioned task into software and hardware module. Also we put forward a new modeling method. Through isolating the internal behavior of system components and communication modes, we implemented a modularization design method.In the third chapter the structure design of the bottom hardware layer of virtual radio experiment system was discussed, including digital up-converter and down-converter module. They not only accomplish up-frequency and down-frequency conversion of digital signal, but also reduce the load of general-purpose processor. They are of favorable programmable ability and suit to kinds of modes.The forth chapter studied the software structure of virtual radio experiment system which is partitioned into three layers. The bottom layer is the kernel mode device driver to control hardware. The middle layer is the user mode device driver to establish data transmittal path. The top layer is application program. The working process of the kernel mode device driver in bottom layer was analyzed. The working flow of the user mode device driver in middle layer and of application program in AM and FM modes in top layer were discussed.In the fifth chapter we discussed the problems of symbol synchronization in software radio system. This is helpful to further implementing the modulation and demodulation of digital signal. A new symbol synchronization method suit to software radio system was put forward, which is based on signal interpolation. The new method use least mean square (LMS) filter instead of traditional multinomial interpolation filter, and apply energy detecting arithmetic to reduce the error code ratio within the delay of half period transmittal. The result of experiment confirms the correctness of the new method by comparing the timing jitter energy and error code ratio.The general work of this paper is summarized and the farther research direction is pointed out in the last chapter.