The New Pre-emphasis Technique Of Long-distance Transimission Based On Pulse-width Modulation Scheme

With the rapid development of seismic observation technologies, the precision of seismic geophone constantly improves, the method of data acquisition gradually updates and the density of detector in exploration area is higher and higher. This brings about huge amount of the problems of data acquisition, transmission and processing. Seismic exploration digital detector not only collects the high precision of weak seismic signal, but also requires high speed data transmission by long seismic cables. Considering the power consumption, the baseband signal is selected to transmit. But in high speed data communication over long seismic cable, inter-symbol interference(ISI) causes the amplitude distortion and phase distortion, thereby greatly reducing the data rate. The data dependent jitter is caused by the reflection and the transmission loss of cable, which further restricts the data rate and transmission distance. This thesis proposes an efficient digital pre-emphasis method, which can effectively improve the speed and reliability of data transmission, and simplify the difficulty in engineering implementation.Based on the pulse-width modulation(PWM) pre-emphasis technology, a method of local PWM pre-emphasis is investigated firstly, which can simplify the complex circuit and reduce power consumption. It uses binary phase shift keying(BPSK) coding signal as an example to determine the best position of pulse-width modulation pre-emphasis through the simulation of simulink. Secondly, in order to further eliminate data dependent jitter, the adaptive local pulse-width modulation pre-emphasis method is putted forward, which can dynamic compensate for the different signal data sequences with strong or weak pre-emphasis. Finally the method of adaptive pulse-width modulation pre-emphasis is extended into multiple-valued data transmission, which is different from the 2nd-order pre-emphasis technology utilizing degrees of freedom in amplitude domain and time domain. It only exploits timing resolution to compensate for the signal integrity, which can reduce the complexity of algorithm. The results of eye diagrams and verification of hardware circuit show the new pre-emphasis method can significantly improve the quality of signal transmission.