Virtual Crystal Oscillator Calibration for Crystal-Less Clock Sync
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Solution Overview
Problem
Existing communication systems require crystals for reference frequency generation, leading to large size and high cost, and existing crystal-less technologies suffer from significant frequency errors that exceed tolerance limits in wireless communication devices, particularly in WBAN applications where ultra-low power and precise clock synchronization are crucial.
Innovation Solution
A crystal-less communication device utilizing an embedded virtual crystal oscillator, which is self-calibrated through a frequency differentiation unit, synthesizer, and signal processing to generate precise clock signals without a physical crystal, allowing for low-cost, highly integrated hardware design and accurate frequency synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a physical crystal is used for reference frequency generation, then frequency stability and synchronization accuracy are improved, but device size and cost increase significantly
Solution Approach 1:
The patent creates a virtual copy of the crystal oscillator function using software algorithms running on the DSP processor. The virtual crystal oscillator (VCXO) emulates the frequency reference function of a physical crystal through digital signal processing, eliminating the need for large physical crystals while maintaining frequency stability requirements
Solution Approach 2:
The patent replaces the mechanical crystal oscillator system with an electronic/software-based system. The virtual crystal oscillator uses digital algorithms and processor operations to generate the reference frequency, substituting mechanical vibration-based frequency generation with electronic computation, thereby reducing physical size while maintaining functional performance
2Area of stationary object
If existing crystal-less technologies are used to reduce device size, then device size and cost are reduced, but frequency error exceeds the ±20 ppm tolerance required for wireless communication
Solution Approach 1:
The patent implements a feedback mechanism where the actual frequency output of the virtual crystal oscillator is continuously monitored and compared against the target frequency. The frequency error is detected and fed back to adjust the oscillator parameters, ensuring the frequency remains within the ±20 ppm tolerance required for wireless communication synchronization
Solution Approach 2:
The patent dynamically adjusts parameters of the virtual crystal oscillator based on detected frequency errors and environmental conditions. By changing operational parameters such as tuning coefficients and compensation values, the system maintains frequency accuracy within tolerance limits while operating without a physical crystal
3Device complexity
If a virtual crystal oscillator is implemented without calibration, then device complexity is reduced, but frequency mismatch and clock synchronization errors increase
Solution Approach 1:
The patent performs calibration of the virtual crystal oscillator during the initialization phase before normal operation begins. The calibration process pre-adjusts the oscillator parameters to account for process variations and environmental conditions, ensuring accurate frequency generation from the start without requiring complex continuous calibration mechanisms during operation
Data Source
AI summary
A communication device uses a local clock generator to regenerate the carrier frequency of the reference signal from a remote communication. In particular, a closed loop is used to self-calibrate the local pulse till the frequency is fixed to be within a fixed frequency margin. Once the local pulse is obtained, the demodulator will use the local pulse to demodulate the reference signal to generate the data signal.