Research Of The Adaptive Equalization Technique Based On QAM Signal

In digital communication, one primary factor that effects data transmission is the inter-symbol interference (ISI). The main reason of ISI is the characteristic of non-ideal channel, which is inevitable mainly because ofmulti-path fading. Presently, adaptive equalization is the main solution of dealing with multi-path fading in wireless communication. It can decrease the effect of ISI and noise, reduce the bit error ratio and trace time-changing channel. So it is necessary to add equalizer to the physical receiver. It can enhance the adaptability of broadband digital transmission apparatus and effectively decrease the performance requirement of channel and receiver, accordingly can reduce cost.The equalization needs training sequence, which is not provided at all time, so the usage of the blind equalizer is necessary. In the sophisticated channel conditions, the blind equalization and its theory is still the problem which should be studied and improved in the communication field, and is also one of the major contents in the dissertation.The work of this dissertation focuses on quadrature amplitude modulation (QAM) signal that is common in communication system and constant modulus algorithm (CMA) the most studied blind adaptive equalization algorithm in recent years. On the base of study and modulation of CMA and modified CMA (MCMA), this dissertation proposes a novel MCMA (NMCMA) which introduces a novel cost function. The cost function includes an additive signal constellation matched error (CME) term, which speeds up convergence rate and corrects rotation of phase. Additionally, the feedback segment is added, which greatly reduces the number of taps and raises convergence rate.Simulation of this dissertation is under MATLAB environment using m language. The Simulation results demonstrate that with litter more computation, NMCMA could increase convergence rate and decrease the steady-state mean square error, improve performance a lot with few taps which establishes theory foundation for project realization. At the meantime, this dissertation pioneered the application of equalization in radar signal. Simulation results demonstrate that the CMA could reduce ISI of bi-phase coding signal in the condition of knowing some parameters.