Logging Cable Manchester Ami Code Decoder

With the development of national economy,petroleum plays a more and more important role as a strategy resource.During the exploitation of petroleum,various data should be gathered using many metrical instruments,and data should be transferred by the cable to the ground.In this condition,different methods will be taken according to different situations in order to control the under-well instruments.The length of common cable is 4000～7000m,so the attenuation of the signal is very large,in order to restore the data of the cable ,we only fall the transmission error rate.In order to reach definite BER index in the situation of known SNR,first we should design the baseband signal reasonably,choose the way of modulation and demodulation.Then we should use the measure of FEQ or TEQ to reduce BER as far as possible,but consider that the working condition of logging cable is bad,if still could not meet the index ,we must use the channel coding technology to reduce BER. Therefore this paper proposed Manchester AMI code decoder.This paper presents the domestic and overseas status of the cable transmission system and the principle of Encoder/Decoder, the key technology and the difficulty in Encoder/Decoder especially. First of all, it elaborates the reasons of ISI in the cable transmission. Then, introduces characteristics and model of the cable channels. last, analyses tramssions of the cable channels.Then,both LMS adaptive algorithm and RLS adaptive algorithm are introduced in theory, as well as the converging performance and tracking performance of them and their improvement form are analyzed. The model of communication system is established with Simulink of Matlab, so the accuracy and reliability of adaptive equalizer system are verified. This paper also introduces design process of adaptive equalizer system in detail, and expatiates the key module. Finally, adaptive equalizer system has been achieved according to the development based on DSP,which eliminates ISI and noise in the cable channles with LMS adaptive algorithm and RLS adaptive algorithm.The result of experiment is analyzed in order to demonstrate performance of adaptive equalizer system.Finally,the paper elaborates the decoder's last step—clock recovery in detail and realizes the decoder system through software,moreover simulates by Matlable The performance index of the system satisfied all design requirements. Furthermore, it can be performed with low cost and easy operation comparing with other congeneric products.