Spread Spectrum Communication System, Fpga-based Encryption

Spread spectrum communication is widely used in all aspects of modern communications because of its good performance in anti-interference, security, low spectral density and large capacity. With the rapid development of information technology, people enjoy the convenience of informationization and also face with problems and risks it brings. The security issue is one of the important aspects, and the core technology is cryptography. It was proved by some facts that the most effective way to ensure confidentiality is to encrypt it with cryptographic algorithms. The rapid development of the EDA technology and FPGA workmanship has provided a new implementation method for the two applications. This paper launchs a series of research of an encryption and spread spectrum communication system based on FPGA. Using the Stratix IV series chips of Altera company as the hardware carrier, and with tools of development, simulation and synthesis, it can implement the related functions of encryption/decryption, frequency spreading and reception in a encrypted spread spectrum communication system.Firstly, the paper researches the performance indexes of encryption spread spectrum communication system, then analyzesthe system work princple.Secondly, the paper researched spread spectrum communication technology. According to RF theory, the paper has completed the system is designed and performance analysis of the RF transmission unit. Characteristics of various types of pseudo-random code are analyzed and compared, and m-sequence is adopted with good autocorrelation. A narrow band digital modulation technique QPSK with low bit error rate is implemented well for the modulation and demodulation of signal during the spread spectrum communication process. The Costas loop is adopted to achieve the received carrier synchronization accurately, and a parallel matched filter is designed to achieve the synchronous capture quickly, and a lead and lag gate is designed and realized in the synchronization tracking section to complete the tracking of the received signal. With EP4SGX70 type FPGA chip as a hardware core, the spread spectrum communication system is completed.Thirdly, the encryption/decryption technology is researched based on 3DES. EP4SE110 type FPGA is adopted as a core chips for related functional verification, and simulation results show that the module could work fast and stable, and has a expected treatment effect. As the same time, it is further discussed how to use the state machines and assembly line to control the encryption/decryption process to improve the processing speed of the algorithm in the paper and finally achieved the optimization of resource usage and the processing speed.