The fact that chaotic systems are realized with finite precisions in digital systems leads to dynamical degradation of the original systems. The most well known problem of the degradation is the existence of short cycle length. To generate pseudo random (PR) sequences for spread spectrum communications and improve its statistical properties, this paper introduces a novel switched chaotic system, which consists of four different subsystems and can change its structure timely and randomly from one to another using two switching functions. Using the switched system, a PR sequence generator is designed and realized based on FPGA (field programmable gate array). This technique is derived from the idea of combining DSP Builder tool with Matlab/Simulink and Quartus II software, and guarantees the generation of repeatable consistent sequences based only on the initial conditions. Furthermore, the proposed PR sequence generator is subjected to four basic statistical tests using the well-known tests suites FIPS-140-1. This PR sequence generator successfully passes all basic statistical tests and can be used in the design of various FPGA-based spread spectrum communications.
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