Direct Digital Synthesizer Phase Alignment
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Solution Overview
Problem
Existing direct digital synthesizers face challenges in maintaining phase alignment across the occupied bandwidth, especially when operating at different frequencies, leading to misalignment and loss of coherence, particularly in multi-channel radio frequency systems.
Innovation Solution
The proposed solution involves a direct digital synthesizer system that includes a phase increment calculator, phase accumulator, phase-to-amplitude converter, and phase preset calculator, which determines phase increments and preset values based on a selected frequency and time offset, allowing for alignment with other synthesizers using residual timing alignment mismatch measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If dense sampling of response versus frequency is used to maintain alignment, then phase alignment at center frequency is improved, but alignment across occupied bandwidth deteriorates
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing phase correction values across the entire occupied bandwidth in lookup tables before operation. This allows the system to quickly retrieve appropriate phase alignment corrections for any frequency within the bandwidth without requiring real-time measurements, thereby maintaining both center frequency alignment and broadband alignment simultaneously.
Solution Approach 2:
The patent changes the parameter approach from single-frequency phase adjustment to multi-frequency phase adjustment by storing multiple phase correction values corresponding to different frequencies within the occupied bandwidth. This enables the system to adapt phase alignment parameters based on the specific operating frequency, resolving the contradiction between center frequency precision and broadband adaptability.
2Reliability
If direct digital synthesizer is reset when modulation data is started, then repeatable phase relationship is achieved, but phase coherence with non-reset channels is lost
Solution Approach 1:
The patent applies preliminary action by pre-calculating phase preset values that account for the expected modulation start time and channel synchronization requirements. These pre-calculated values are stored and applied to ensure that when modulation begins, all channels are already positioned to maintain phase coherence, eliminating the need to reset channels and preserving both repeatable phase relationships and inter-channel coherence.
Solution Approach 2:
The patent uses feedback by measuring the actual phase relationships between channels and using this information to adjust phase preset values for future operations. This feedback mechanism ensures that phase alignment is maintained across all channels while preserving the repeatable phase relationship needed for reliable operation.
3Measurement precision
If different calibration is performed for each different frequency, then frequency-specific alignment is improved, but system complexity increases
Solution Approach 1:
The patent applies preliminary action by performing all frequency-specific calibrations in advance and storing the results in lookup tables. During operation, the system simply retrieves the appropriate calibration data for the current frequency rather than performing complex real-time calculations, thereby achieving frequency-specific alignment precision while keeping the operational system complexity low.
Solution Approach 2:
The patent uses copying by creating lookup tables that contain pre-calculated phase correction values for different frequencies. Instead of performing complex calibration calculations for each frequency during operation, the system copies and applies the appropriate pre-stored calibration data, reducing computational complexity while maintaining frequency-specific alignment precision.
Data Source
AI summary
A direct digital synthesizer transmits a signal. The direct digital synthesizer includes a phase increment calculator, a phase accumulator, a phase-to-amplitude converter (PAC) and a phase preset calculator. The phase increment calculator determines a phase increment for a selected frequency. The phase accumulator accumulates the phase increment over time and provides an accumulated phase value. The phase-to-amplitude converter (PAC) converts the accumulated phase value to a periodic signal having the selected frequency. The phase preset calculator determines a phase preset value for the selected frequency of the periodic signal and a provided time offset for a time specified by a controlling event. The direct digital synthesizer is aligned with another direct digital synthesizer using the time offset based on measurements of a residual time alignment mismatch between the signal and another signal transmitted by the other direct digital synthesizer.