| Summary: | 碩士 === 國立海洋大學 === 電機工程學系 === 85 === An equalizer is a structure used in digital communication
systems foreliminating the intersymbol interference(ISI)
generated in the channel. Itsperformance is usually nastered by
the adopted adaptive algorithm. Therefore, equalizers using
different algorithms may have different limitations on their
applications. Every conventional adaptive algorithm may have
its own disadvantage,such as low convergence rate(e.g., LMS),
high computational complexity, and numerical instability(e.g.,
RLS). Aiming ata these shortcomings, we propose atransform-
domain approximate RLS(TARLS) algorithm. The proposed methodis
shown to be behave similarly to the RLS in terms of convergence
rate whilekeeping its computational complexity to be of the same
order as that of LMS.Besides, we also consider the performance
of the proposed method under the environment of finite
precision. We find that the proposed method can be immune from
the possible numerical instability introduced by the
quantization error. The proposed method is also used to replace
LMS type algorithm employed in a blind equalizer. Such a
combination is proven to be able to improvenot only the low
convergence rate of the blind equalizer but also the
numericalinstability caused by finite precision. In addition, in
view of the fact that a simple structure is often preferred for
real-time implementation of equalizers,we implement some LMS
type and blind equalizers by using a digital signal processor(
DSP). Real-time processing of data signals is achieved in all
cases. We use computer simulation to verify that the
proposed method, whenbeing applied to a system identification
task can indeed perform better than theLMS and RLS algorithm do.
By simulating the QPSK signal passing through a multipath fading
channel, the superiority of the por posed method over the
conventional method is demonstrated. At last, by using a signal
processingsoftware, we demonstrate the feasibility of using
digital signal processors toimplement real-time processing
adaptive equalizers.
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