الفهرس 
Communication Channels ImpairmentsOnly 14 pages are availabe for public view
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Abstract
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The output of the matched filter at the receiver is greatly
distorted due to channel impairments such as noise, inter-symbol
interference, non-stationarity in the channel. That is due to the fact
that the matched filter is designed to be matched with the
transmitted signal.
Adaptive filter may be used to avoid these drawbacks caused
by the channel since it has the ability to track the channel variation.
The present thesis presents two different systems based on using
adaptive filter together with the matched filter at the receiver. In the
first system, BARKER code is used to modulate four level data. At
the receiver, the adaptive filter is used after the matched filter and
adapts it’s output as the ideal auto-correlation function of the
BARKER code. The basic idea in the adaptation process is based
on the shape of the auto-correlation function, which has alternative
zeroes. So, the adaptive filter adapts it’s output to zero at these
instants and stops adaptation at the next instants thus solving the
problem of the distortion in the matched filter output. The main
advantage of this method is that the adaptation processor of the
adaptive filter will modify the tap weights each double the baud
interval i.e., slower processor is sufficient to be used.
In the second system, M-sequence is used to modulate
binary data by using an EXOR gate. To recover the binary data at
the receiver, an adaptive filter is used before a modified matched
filter (MMF) to minimize the distortion caused by the channel
impairments. The main advantage of this method is the simplicity
in modulation and increasing security in data handling. Each of the
two systems is derived mathematically and simulated on digital
computer to measure the performance. Some computer simulation
results are shown to demonstrate the effect of various parameters
on the performance of the system. The results show that an
improvement is achieved on the performance for both stationary
and non stationary channels.