Resonator-Based Digital Frequency Synthesis With Temperature Compensation
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Solution Overview
Problem
Traditional phase locked loops (PLLs) in communication applications face limitations due to low Q of on-chip inductors, leading to high phase noise, and high Q off-chip devices like crystals have frequency variations with temperature and manufacturing variability, affecting the accuracy and stability of output signals.
Innovation Solution
A direct frequency synthesizer using high speed resonators like BAW, FBAR, or SMR, which generates a frequency signal, adjusts for temperature and resonant frequency variations through frequency compensation circuitry, and integrates with a PLL for improved phase noise performance and frequency stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If on-chip L-C tank circuitry is used for VCO implementation, then integration is improved, but phase noise performance deteriorates due to low Q of on-chip inductor
Solution Approach 1:
The patent introduces a digital frequency synthesizer as an intermediary component between the low-Q on-chip VCO and the final output signal. This synthesizer processes the VCO output digitally to generate the final signal, effectively decoupling the phase noise performance from the VCO's Q limitation and allowing integration of the entire system on-chip.
2Reliability
If off-chip high Q devices like crystals are used as reference, then phase noise performance is improved, but frequency stability deteriorates due to temperature variations and manufacturing variability
Solution Approach 1:
The patent implements a feedback mechanism where the actual frequency of the resonator is measured and compared with the desired frequency. A frequency control word is generated based on this comparison and used to adjust the digital frequency synthesizer, creating a closed-loop system that compensates for frequency drifts due to temperature and manufacturing variations.
Solution Approach 2:
The patent changes the operating parameters of the system by using digital frequency control instead of analog voltage control. The frequency control word adjusts the digital synthesizer's operation to compensate for resonator frequency variations, maintaining stable output frequency despite environmental changes.
3Measurement precision
If digital frequency synthesizer with frequency compensation is used, then frequency accuracy is improved, but device complexity increases
Solution Approach 1:
The patent replaces traditional analog frequency control mechanisms with a digital frequency synthesizer. The digital system uses a frequency control word to precisely control the output frequency, substituting complex analog compensation circuits with digital processing that achieves the same frequency accuracy with reduced component complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution provides a programmable oscillator with low phase noise, precise frequency control, and temperature compensation, enabling high accuracy and stability in output signals across varying temperatures and resonant frequencies, replacing traditional crystal and quartz oscillators with cost savings and improved performance.
Implementation Method 1
A high speed resonator generates a frequency signal
Implementation Method 2
frequency compensation circuitry generates a frequency compensation value to adjust for errors in the frequency signal generated by the high speed resonator
Data Source
AI summary
Systems and methods for digital synthesis of an output signal using a frequency generated from a resonator and computing amplitude values that take into account temperature variations and resonant frequency variations resulting from manufacturing variability are described. A direct frequency synthesizer architecture is leveraged on a high Q resonator, such as a film bulk acoustic resonator (FBAR), a spectral multiband resonator (SMR), and a contour mode resonator (CMR) and is used to generate pristine signals.