The novel feed forward and decision feedback equalizer structures and improved variable step algorithm

Abstract

Skin effect and dielectric loss in super-long cable will cause nonlinear attenuation at different signal frequency, and in addition, coupling noise and thermal noise also cause signal distortion at the receiver end. These factors seriously affect the signal transmission speed in the super-long cable. Especially, in the field of exploration of shale gas and bed methane, the transmission cable is also used to transport high-precision synchronization pulse signal, and the synchronization pulse must reach the microsecond accuracy, which is used for data phase calibration. A synchronization signal is a high frequency signal, which suffers more severe attenuation and noise interference. At the receiving end, the sync pulse signal will be drowned in the noise environment, and so it is difficult to restore the original signal.#br#Although fiber can achieve a high transfer rate, but the fiber cable cannot transmit power energy; in addition, the tensile strength and heat resistance of the fiber are much worse than copper cable, these weaknesses limit its application in such industry. Therefore, an effective balancing algorithm is necessary to overcome the propagation effects and interference in a super-long copper cable. However, conventional equalization techniques have well-balanced effect for the short-range communications, but for the long-distance communication, they often have poorly balanced results. In order to solve the above problem and improve the long cable signal transmission speed, this paper presents a new balanced portfolio structure; the new structure uses feed-forward equalizer (FFE) as the pre-stage, and decision-feedback equalizer (DFE) as the post stage to form a new structure. The combination structures can effectively utilize the flexibility of FFE and overcome the problem of error diffusion in DFE. By mathematical modeling and simulation, this paper gives the best combination factors. Furthermore, based on the improved structure, a new convergence algorithm is proposed, which uses the arc tangent function combined with three error converge factors to form a converging function, and it has the advantages of fast convergence and steady-state error. Simulation results show that the FFE-DFE combination equalizer has low computational complexity, fast convergence, and strong channel tracking capability; in addition, it can speed up the data processing speed, and better respond to the real variation of the channel. Simulation results show also that the performance is improved by 50% by eliminating inter-symbol interference and noise.#br#The real circuit board based on the new algorithm have been tested in the East China Petroleum Bureau, the test results show that the algorithm can rectify 160 dB signal distortion, and the transmission speed can reach 5 Mbps in 6 dB signal to noise ratio.