A Rearch And Implementation Of Adaptive Echo Cancellation Algorithm Based On The RF Repeater Of The Same Frequency

Now, it is the Information Age, the mobile communications is developing at a rapid pace. However, the signal is impossible to cover all regions, so there are a weak signal area and the blind area. For these areas, we usually use the repeater which enhances the power of RF signal. It solves weak coverage problems by this way, but it brings echo signal, which results in the unnormal reception of an effective repeater signal. In communication systems, echo has always been an unavoidable topic.At present, the universal way is to use adaptive echo cancellation technology to cancel echo.In this paper, based on RF repeater with the same frequency, we takes DVB-T standard as example and talks about a echo cancellation technology that is to add echo cancellation module based on the FPGA and DSP. Taking into account echoes are constantly variable,while the adaptive filter can track to the real-time changes in echo signal,thus the adaptive algorithm has been widely applied in echo cancellation.This paper mainly studies the adaptive echo cancellation algorithm based on the RF repeater with the same frequency and its implementation process.The choice of adaptive algorithm will directly affect the results of the echo cancellation system.It is needed to think about the following points when choosing adaptive algorithm: the convergence rate, the stability of the system and the complexity of the algorithm.The algorithm is required to implement easily and to reduce the costs of system.Now, there are a number of adaptive algorithms and the corresponding improved algorithms. Such as the LMS algorithm (Least Mean Square), NLMS algorithm (Normalized Least Mean Square ), BLMS algorithm (Block Least Mean Square), variable step-size algorithm, RLS algorithm (Recursive Least Squares).This paper introduces some echo cancellation technology based on the same frequency RF repeater, takes the DVB-T as example and achieves the signal through the Matlab simulation; Second, it briefly introduces echo cancellation scheme, which is achieved on the platform of the FPGA and DSP; then, we focuse on the basic principles of adaptive filters as well as some common basic adaptive algorithms. We compare their respective advantages and disadvantages of adaptive algorithm by the simulation of Matlab, and adopt an improved variable step size based on transform domain adaptive algorithm which shows it has faster convergence, smaller steady-state error by the simulation of Matlab, favorable performance in echo cancellation. That achieves a compromise between the convergence speed and steady-state error; Finally, based on CCS software, it achieves echo cancellation based on the DSP by designing C program of adaptive algorithm.