An Inmproved Vehicle Passive Keyless Entry System Research

Modern car entrance guard system is mainly divided into two kinds of entrance guard system active and passive entrance guard system.The earliest active entrance guard system is mainly used for mid standard and low standard cars, passive entrance guard system is mainly used in high standard cars.As the car as a decline in the cost of electronic products and the improvement of application requirements, passive entrance guard system gradually appear in the mid- standard cars now.In the passive entrance guard system based on the research in the market now found the system still has many defects, Such as its single carrier frequency of communication,Modulation method is most simple ASK modulation Spectrum bandwidth utilization rate is low, anti-interference ability is not strong. Already a lot of illegal car on the market entrance guard system interference of electronic equipment is available. The main significance of this thesis is how to make use of electronic technology, against the radio interference.The thesis mainly uses spread spectrum technology to improve the existing automobile passive entrance guard system.Mainly studied the principle of spread spectrum communication, spread spectrum technology, especially the kinds of frequency hopping technology.Main content including channel convolution code coding, channel decoding Viterbi algorithm, the principle of pseudo-random sequence, the mathematical model and algorithm implementation of m sequence, the principle and realization of the FSK modulation, spread spectrum code synchronization capture and synchronous tracking method, and the solution of frequency hopping codes, demodulation process and the realization of the algorithm, rolling code encoding and decoding principle and the realization of the algorithm.This thesis compared with the existing passive on the market access system can help the whole system greatly improve the ability of anti-jamming. Using of frequency hopping technology, greatly improve the channel bandwidth, the initiative to avoid interference, which is only based on the software algorithm, hardware cost is not increased because of the transformation, in now based on the cost of improving the anti-jamming ability of the system.