Abstract
A 2-bit adaptive sigma delta modulation system that inherently eliminates the idle tones present in conventional and other adaptive sigma delta systems is described. The system incorporates both memory and look-ahead instantaneous step-size estimations and, as shown by computer simulation results apart from eliminating the unwanted idle tones despite dithering, it offers improved SNR performance and extended dynamic range.
Highlights
Sigma-delta modulation (SDM) is extensively used in various applications due to its high resolution and relatively simple analog implementation
A good example of a multibit Adaptive sigma-delta modulation (ASDM) that originated from a similar adaptive delta modulation (ADM) scheme is the 2-bit ASDM system by Aldajani and Sayed [5, 6], the quantizer of which follows a forward or look-ahead step-size estimation and generates 2-bit output codewords with information about both the sign and the relative magnitude of the step-size resulting in an exponential step-size variability
One of the advantageous features of that system has been its inherent ability to eliminate the periodic pattern that characterized the quantization error of the widely known Jayant’s ADM with 1-bit memory [9, 10]. Motivated by this particular feature and following the aforesaid relation between delta and sigma-delta modulation, in this paper we propose a 2-bit ASDM system based on our recently presented 2-bit ADM in order to examine its operational characteristics and, to investigate in tonal behavior, that is, the generation of output idle tones for DC input signals
Summary
Sigma-delta modulation (SDM) is extensively used in various applications due to its high resolution and relatively simple analog implementation. Adaptive sigma-delta modulation (ASDM) is considered as an alternative to SDM offering increased dynamic range and reduced quantization noise at the expense of some added complexity [1] This is achieved by varying the step-size of the basic two-level quantizer according to a decided rule. One of the advantageous features of that system has been its inherent ability to eliminate the periodic pattern that characterized the quantization error of the widely known Jayant’s ADM with 1-bit memory [9, 10] Motivated by this particular feature and following the aforesaid relation between delta and sigma-delta modulation, in this paper we propose a 2-bit ASDM system based on our recently presented 2-bit ADM in order to examine its operational characteristics and, to investigate in tonal behavior, that is, the generation of output idle tones for DC input signals.
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