MEMS Oscillator Frequency Margining for Spur Suppression
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Solution Overview
Problem
Fractional-N frequency synthesizers generate unwanted low-frequency spurs, making them impractical for many applications unless these spurs are suppressed to a negligible level, which existing techniques struggle to achieve effectively.
Innovation Solution
A MEMS-based oscillator circuit with bidirectional frequency margining capabilities, utilizing a dual-function output enable/frequency margining pin and an active-low margining enable pin to synchronize and control incremental or decremental changes in the frequency of the periodic output signal, allowing for real-time frequency adjustments without additional pins, thus supporting fine control of output frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If fractional-N frequency synthesizers are used to achieve fine frequency resolution, then frequency resolution is improved, but unwanted low-frequency spurs are generated
Solution Approach 1:
The patent implements bidirectional frequency margining that dynamically adjusts the output frequency of the oscillator circuit in real-time. The frequency can be incremented or decremented based on control signals, allowing the system to adaptively tune the frequency to avoid spur generation while maintaining fine frequency resolution. This dynamic adjustment capability resolves the contradiction by enabling the system to operate at frequencies that minimize spur effects.
Solution Approach 2:
The patent changes the frequency parameter of the oscillator output by controlled amounts (frequency margining) to suppress spurs. By adjusting the frequency away from problematic values and maintaining fine resolution through precise control mechanisms, the system achieves both high frequency resolution and spur suppression. The bidirectional capability allows optimization in both frequency directions.
2Object-generated harmful factors
If frequency margining is implemented to suppress spurs, then spur suppression is improved, but device complexity increases due to additional pins and control circuitry
Solution Approach 1:
The patent integrates frequency margining functionality into the existing output enable pin of the oscillator circuit, making this pin serve dual purposes: enabling/disabling the output and controlling frequency margining. This multi-functionality approach eliminates the need for additional dedicated pins for frequency control, thereby suppressing spurs without significantly increasing device complexity. The same control infrastructure is reused for both output control and frequency adjustment.
3Productivity
If real-time frequency adjustments are made without rebooting, then productivity is improved, but control precision becomes more difficult to maintain
Solution Approach 1:
The patent implements a feedback mechanism where the oscillator circuit continuously monitors and adjusts its frequency based on control signals while maintaining lock. The bidirectional frequency margining allows real-time frequency changes with feedback control that ensures precision is maintained during dynamic operation. The system can increment or decrement frequency in controlled steps while maintaining stability, achieving both real-time adjustability and precision control.
Data Source
AI summary
Integrated circuit devices include a packaged MEMS-based oscillator circuit, which is configured to support bidirectional frequency margining of a periodic output signal. This bidirectional frequency margining is achieved using a first signal to synchronize changes in a frequency of the periodic output signal and a second signal to control whether the changes in the frequency of the periodic output signal are incremental or decremental. In particular, the oscillator circuit may be configured so that each change in the frequency of the periodic output signal is synchronized to a corresponding first voltage transition of the first signal and a voltage level of the second signal may be used to control whether the changes in the frequency of the periodic output signal are incremental or decremental.