Staggered Nyquist Regions in DAC Synthesizers
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Solution Overview
Problem
Conventional waveform synthesis systems using digital-to-analog converters (DACs) are limited by guard bands, which create inaccessible spectrum regions and restrict the frequency range due to the need for guard bands, preventing the generation of signals near or within these regions.
Innovation Solution
Staggering consecutive Nyquist regions by varying the DAC clock frequency allows overlapping of guard bands, enabling the use of selective reconstruction filters to recover guard band spectrum, thereby extending the usable frequency range without introducing additional noise or attenuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard bands are used to suppress images in conventional DAC systems, then image suppression is improved, but the usable frequency range is reduced due to inaccessible spectrum regions
Solution Approach 1:
The patent dynamically switches between multiple DAC clock frequencies (first clock frequency and second clock frequency) to operate in different Nyquist regions. This dynamic adjustment allows the system to access frequency ranges that would otherwise be blocked by guard bands, resolving the contradiction between maintaining reliable image suppression and expanding the usable frequency range.
Solution Approach 2:
The patent divides the frequency spectrum into multiple Nyquist regions by using different clock frequencies. Each clock frequency creates a distinct Nyquist region with its own guard bands, allowing the system to segment the overall frequency range and access different portions sequentially, thereby overcoming the limitation of a single continuous guard band restriction.
2Productivity
If the DAC operates near the Nyquist limit to maximize frequency output, then frequency range is improved, but signal quality deteriorates due to guard band induced holes and attenuation
Solution Approach 1:
The system dynamically selects between different clock frequencies based on the desired output frequency. When operating near the Nyquist limit of one clock frequency, the system can switch to a different clock frequency whose Nyquist region provides better signal quality for that frequency range, thus maintaining both high frequency range and signal quality.
Solution Approach 2:
The patent creates multiple copies of the DAC output by using different clock frequencies, each producing a version of the signal optimized for different frequency ranges. By selecting the appropriate copy (clock frequency) for each operating condition, the system avoids guard band induced holes and maintains signal quality while extending the overall frequency range.
Data Source
AI summary
Staggered consecutive Nyquist regions associated with differing DAC synthesizer clock rates (FCLK) avoids spectrum lost through disjoint guard bands at the end of or between adjacent Nyquist regions. The staggered consecutive Nyquist regions overlap by an amount at least as much as is consumed by the guard bands. Selectable reconstruction filters associated with each Nyquist region and its DAC clock rate are used to enforce the staggered Nyquist regions and their various guard bands.