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Title:Direct Digital Synthesis And Spur Reduction Using Method Of Dithering
Author(s):Patel, Karnik Radadia Aka
Contributor(s):Schutt-Aine, Jose
Subject(s):signal synthesis
direct digital synthesis
spur reduction
Abstract:Many application, including communication, test and measurements, and radar require the generation of sinusoidal signal with high degree of spectral purity. One method for producing source signal with high purity is by using technique of Direct Digital Synthesis. The method of Direct Digital Synthesis for generation sinusoidal signal uses a very simple circuit, it is easy to control, has stable performance, high frequency conversion speed and fine accuracy. The standard approach to implement a Direct Digital Synthesizer is to truncate the output of phase accumulator to reduce the size of lookup table and truncate the output of lookup table to match number of input bits of Digital to Analog Converter. This process generates spurs and degrades the quality of signal at the output of Direct Digital Synthesizer. One way of reducing the spurs in Direct Digital Synthesizer without increasing the size of look-up table is by quantizing the summed output of a dither generator and phase accumulator before sending the resultant multi-bit signal to the lookup table or by quantizing the summed output of a dither generator and lookup table before sending multi-bit signal to the Digital to Analog Converter. By adding the output of dither generator i.e. by adding a pseudo-random sequence to the Direct Digital Synthesizer the truncation spur can be can be randomized and converted to noise throughout the available bandwidth, thereby increasing the floor noise and improving the signal resolution.
Issue Date:2012-12
Publication Status:unpublished
Peer Reviewed:not peer reviewed
Date Available in IDEALS:2014-01-09

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