The Research And Application On An Improved Equalization Method For Direct Conversion Receiver

In the wireless and mobile communication system, signal is vulnerable to environmental randomness and multi-path interference effects in the transmit process, such as multipath effect. Common direct conversion receiver, signal are susceptible to dc voltage deviation, the leakage of vibration and noise, causing received signal distortion and interference between operator number, so it is necessary to balance the output of the baseband signals at the receiving end to the direct conversion receiver, improve the data processing speed, reduce the bit error rate, improve the efficiency of system, makes the receiver of the baseband signal compensation is more effective. Adaptive equalization is a very effective means to obtaining-information junction compensation signal to intersymbol interference, in the receiving output signal can be supplemented and correct the distortion, to restore the original signal.This paper proposes a modified equilibrium method that is suitable for the direct conversion receiver output signal distortion. Frequency equalization method usually used forward feedback equalizer(FFE) or decision feedback equalizer(DFE) common equalizer. FFE and DFE have their advantages and disadvantages, the forward feedback equalizer has simple structure, can eliminate not severe intersymbol interference, but processing the severe intersymbol interference power is not enough; Decision feedback equalizer can eliminate the severe intersymbol interference well, but realizing the wrong front end, because error diffusion result in wrong judgment. Considering the advantages and disadvantages of the above two kinds of equalizer, this paper adopted the ways of optimizing the FFE and DFE combined equalizer. Although FFE and DFE combined equalizer can better compensation signal, in the case of channel distortion and noise pollution, wrong decision feedback diffusion and the residual intersymbol interference will lead to the equalizer have serious performance degradation.This article first has carried on the structure to the equilibrium structure of internal improvements, in the structure on the join bayesian decision FFE-DFE-Beyes equalizer. Improve the balance of equalizer by bayesian decision device performance, reduce the bit error rate, improve the compensation performance, eliminate residual intersymbol interference, reduce the wrong judgment test feedback. Secondly, based on this structure, an improved Marr function of variable step size least mean square error algorithm. Will be based on Marr function of variable step size LMS algorithm is used for combining the FFE-DFE-Beyes equalizer, it can accelerate the convergence speed, faster processing data, and channel tracking performance and good adaptive ability, it can better track real-time changes in the wireless communication system.Simulation and hardware implementation results show that the variable step size algorithm based on Marr improvement FFE- DFE- Beyes equilibrium method can effectively compensate the receiver baseband signal distortion, improve the convergence speed, intersymbol interference suppression, and removed noise.signal recovery is good and the overall balance effect is obvious.