Thesis
Low-power phase accumulator for direct digital frequency synthesizers
Washington State University
Master of Science (MS), Washington State University
2013
Handle:
https://hdl.handle.net/2376/100808
Abstract
Direct digital frequency synthesizers (DDFSs) can produce sinusoidal waveforms over a wide range of frequencies, as well as have higher frequency resolution and lower phase noise than phase-lock loop based frequency synthesizers. However, their higher complexity and power dissipation are drawbacks. A DDFS consists of a phase accumulator (PA), a look-up table (LUT) and a digital-to-analog converter. Among these components, PAs dissipate a substantial portion of the power. A novel approach to implementing the PA is presented that reduces power dissipation, complexity and layout area. A phase accumulator consists of an adder and a register to hold the previous sum. Fast carry-look-ahead adders (CLAs) may not be fast enough for some applications so pipelining and/or parallelism are used. Fast CLAs and pipeline registers result in high power dissipation. Our approach uses carry save adders for the lower bits in the calculation which reduces complexity substantially but causes a delay in the carry to the least significant bit of LUT input. The degradation to the spurious free dynamic range due to this delay is shown to be very small. The approach can be applied to both pipelined and parallel architectures. Comparisons of power dissipation and layout area are presented for 32-bit parallel PAs in 0.l8um CMOS technology operating near 2GHz. The spurious free dynamic range degrades by only 0.2dB while the power dissipation reduction is in the range of 10% to 30% and the size reduction is about 13%. The lower power dissipation and less complexity of this approach will help to bring the advantages of DDFSs to more synthesizer applications in the future.
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Details
- Title
- Low-power phase accumulator for direct digital frequency synthesizers
- Creators
- Xu Meng
- Contributors
- George S. La Rue (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Electrical Engineering and Computer Science, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; [Pullman, Washington] :
- Identifiers
- 99900525129601842
- Language
- English
- Resource Type
- Thesis