The Software Design Of Vector Signal Generator SDR-based

With the rapid development of wireless communication technology, the digital modulation Schemes become increasingly rich. To accomplish the function of modulation and demodulation in hardware became more and more difficult and complicate. However, it is greatly enhanced the flexibility of communication system design in software. Today, the vector signal generator has been widely used in the process of testing and debugging a digital communication system, the baseband signal generator is the critical components of the vector signal generator. It provides a corresponding baseband signal to a digital I/Q modulation, or be output directly.In this dissertation, a baseband signal generation process which was based on software radio platform was developed with LabVIEW software. The main contents are as follows:1. The research of pseudo-random sequence generation techniques, it provides different code sources for users, PN9, PN13, PN25, besides user-defined sequence.2. The research of several conventional digital modulation formats such as MASK, MFSK, MPSK, MQAM, etc. established the different mapping between the baseband signal and symbol code. And the multi-order modulation signal, artificially channel noise and I/Q impairment injection were achieved in software.3. The research of shaping filtering techniques in the baseband signal generation. The main function of shaping filter are reducing the inter-symbol interference in baseband signal transmission process and improving the utilization of the spectrum. The design called directly the sub-vi of Raised cosine filter and FIR filtering to build baseband signal shaping filter, and the simulation results were verified by MATLAB.4. Built a test platform. Tested the function and signal quality of the design and confirmed the feasibility of the design.After the final test, the digital baseband signal generator can support the ASK, FSK, PSK, QAM and other formats modulation, and the quality of signal can meet the design requirements. The maximum sample rate is up to 20MS/s, the maximum symbol rate is up to 25 MHz, the EVM values were less than 6%, the design meet the requirements.