Study Of Software Defined Radio Transmitter Using Direct Sequence Spread Spectrum Based On FPGA

SDR (Software Defined Radio) is the third revolution in wireless communication area after the former two revolutions as the first one is from stable to mobile and the second one is from analog to digital. It is the new direction of wireless communication not only in these days but also in the coming years. It has unmatchable advantages in improving the system flexibility and offers a effective way to realize the future wireless communication system. Considering its excellent features in noise resistance, secrecy and spectrum efficiency comparing to the traditional narrowband technology, spread spectrum will be the key technology in the future wireless communication systems. DSSS (Direct Sequence Spread Spectrum) is the most popular type of the spread spectrum technology in civil use. FPGA has become the first choice for designing the SDR system because of its unique advantages in distributed computing, parallel processing and pipelining.This article firstly introduces the theory foundation of SDR, analyzes its hardware construction and main technology. The key idea of SDR is to design a common and powerful hardware platform, which is also one of the main tasks in this project. The article also discusses the DSSS theory. For the transmitters, to find a pseudo-noise code that has fabulous performance if correlation properties is most critical. OVSF code, Gold code and m sequence are deeply studied. Furthermore, FPGA technology and digital modulation technology based on DDFS are described in detail.Based on the above works and the hardware construction of SDR, I have designed the hardware platform using Altera's Cyclone FPGA. The platform is composed of 210 Mbps high-speed DAC, UART, USB interface, audio CODEC input/output channels, LVDS interface and SDRAM. In order to...