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针对测井电缆信道传输量小,电缆传输信号易产生衰减和畸变等问题,通过对正交频分复用(OFDM)技术原理和井下电缆传输特性的分析,利用Altera公司开发的DSP Builder软件搭建了一个基于OFDM技术的井下遥测系统,分析信道传输特性,给出了不同编码调制方案的测试结果。结果表明在信噪比相同的情况下前向纠错编码(FEC)抗噪性能最好,降低了接收端的误码率(BER),提高了系统的可靠性,保证了井下数据的有效传输。
Aiming at the problems of small transmission volume of the cable in the logging cable and easy attenuation and distortion of the cable transmission signal, the paper analyzes the principle of Orthogonal Frequency Division Multiplexing (OFDM) and the transmission characteristics of the cable in the downhole, and builds DSP Builder software developed by Altera A downhole telemetry system based on OFDM technology is used to analyze the channel transmission characteristics and the test results of different coding modulation schemes are given. The results show that FEC is the best one with the same SNR, which reduces the bit error rate (BER) at the receiving end, improves the system reliability and ensures the effective transmission of downhole data.