Abstract
A 2-bit adaptive delta modulation system with improved performance is proposed in this paper. Its main characteristic is a new adaptation algorithm that incorporates both memory and look-ahead instantaneous step-size estimation and leads the modulator into generating a 2-bit output codeword. As shown by computer simulation results, the proposed system offers reduced overshoot and fast response to signal variations in comparison to other similar systems.
Highlights
Adaptive delta modulation (ADM) is a common alternative to fixed step-size delta modulation (DM) offering increased dynamic range and reduced slope-overload noise at the expense of some added complexity
The 2-bit ADM system described by Aldajani, [9, 10], generates output codewords consisting of two binary digits which carry information about the sign of the error signal e(n) = x(n) − y(n) as well as its absolute value, so that the step size is determined at each sampling period according to the rule
Based on the adaptation algorithm of the 2-digit ADM system presented above, we propose a modification that eliminates the need of a ternary digit in the generated output codeword at the expense of a slightly inferior signal-to-noise ratio (SNR) performance
Summary
Adaptive delta modulation (ADM) is a common alternative to fixed step-size delta modulation (DM) offering increased dynamic range and reduced slope-overload noise at the expense of some added complexity. Various modifications and extensions of that basic instantaneously adaptive scheme have been proposed in the literature including 2- or 3-bit ADM and 2-digit ADM [2,3,4,5,6,7,8] These multidigit systems provide for a variable rate in step changes between adjacent sampling instants incorporating various forms of “memory” and/or “look-ahead” stepsize estimation, that is, feedback and/or feedforward adaptation, respectively, and offer enhanced overall performance in normalized comparison to single-bit adaptive DM [6,7,8].
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