The Research About Rectification Algorithm Of HDB3 Signals On The Long Line Transmission Systems

The signal's high frequency part attenuates seriously on the receiver of the non-repeater long line transmission systems, so that signal rectification is necessary to the non-repeater long line transmission systems.The research background of this thesis is observation and sampling cable system of the seabed 6000 meters deep, television grab bucket. The main task of this paper is to set up a real time rectification algorithm, in the light of the waves of the distorted HDB3 signals which are transferred from a myriameter coaxial-cable and the character of HDB3 coding signals. The characters of long line transmission is equal to lowpass filter, so the rectifier to the HDB3 signals is a highpass filter, and the transfer function of this highpass filter is reverse to the character of long line transmission. But to design such a highpass filter is difficult.This paper is to design a rectification algorithm directly, avoiding the filter and according to the distorted waves of the HDB3 coding signals. Several rectification methods are compared to show their advantages. Threshold method is the basic one of the sampling decision. It can conveniently identify the signals with distinct peak value. Inflexion method fused with pace factor can represents the wave character of the distorted signals. Comparing the numbers of its inflexion can identify different symbols. When the symbols are detecting by the HDB3 coding rules, the error-decision symbols will influence the follow symbols'identification, the error accumulation effect comes forth. By dividing the HDB3 data flow into some small sects, the error accumulation effect will be controlled at each small sect, symbols'effective decision will be realized. A synthetic rectification algorithm is proposed by the discussion of effective integration to the several rectification methods. In this algorithm, inflexion method fused with the superiorities of threshold method and pace method is the main part. The decided symbols are detected and the error-decision symbols will be corrected by the HDB3 coding rules. The entire algorithm is simulated and its efficiency is validated in the MATLAB environment.At last, based on the comparison of CPU, DSP and FPGA, this paper puts emphasis on the research about the method of the synthetic rectification algorithm on the FPGA. Through the integration between software and hardware, according to the low-level highpass filter, a rectification project of the distorted HDB3 coding signals on the non-repeater long line transmission system, is presented.