Dual-Current VCO Filtering for Low Jitter and Frequency Stability
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Solution Overview
Problem
Conventional voltage-controlled oscillators (VCOs) face challenges in achieving low jitter while being resistant to variations in manufacturing processes, temperature, and voltage, often requiring additional frequency-calibration circuits and larger loop filters, which increase cost and circuit size.
Innovation Solution
A voltage-controlled oscillator (VCO) and phase-locked loop (PLL) design that utilizes a dual current supply circuit and a VCO filter to differentiate between slow and rapid changes in input voltage, allowing for high gain against slow changes and low gain against noise-induced jitter, eliminating the need for external capacitors and additional calibration circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a low-gain VCO is used to reduce output jitter, then the jitter performance is improved, but the VCO becomes vulnerable to frequency variation caused by manufacturing processes, temperature, and voltage
Solution Approach 1:
The patent implements dynamic gain control by switching between first and second gain values based on operating conditions. The VCO gain is adjusted according to temperature and voltage levels, allowing the system to maintain frequency stability under varying conditions while achieving low jitter when needed. This is accomplished through a control circuit that monitors operating parameters and dynamically selects appropriate gain settings.
Solution Approach 2:
The patent changes the gain parameter of the VCO based on temperature and voltage conditions. By adjusting the gain value according to environmental parameters, the system optimizes both frequency stability and jitter performance. The control circuit modifies the VCO gain parameter dynamically, selecting from multiple predetermined gain values to match current operating conditions.
2Stability of the object's composition
If a high-gain VCO is used to resist variation of manufacturing processes, temperature, and voltage, then the frequency stability is improved, but the output jitter increases and a large-size loop filter is required
Solution Approach 1:
The system dynamically adjusts the VCO gain based on operating conditions, switching between high and low gain values as needed. This allows the system to achieve both frequency stability and low jitter performance by adapting the gain parameter in real-time according to temperature, voltage, and jitter requirements.
Solution Approach 2:
The patent implements parameter changes by selecting from multiple predetermined gain values based on current operating conditions. The control circuit adjusts the VCO gain parameter to optimize performance, using higher gain values for frequency stability and lower gain values for reduced jitter, thereby eliminating the need for large loop filters.
3Reliability
If the VCO gain is decreased to achieve low jitter, then the jitter performance is improved, but the gain must be kept above a certain level to tolerate variation of temperature and voltage
Solution Approach 1:
The system dynamically adjusts the VCO gain based on monitored temperature and voltage conditions. When environmental variations are detected, the control circuit increases the gain to maintain frequency stability. When stability is sufficient, the gain is reduced to minimize jitter. This dynamic adaptation allows the system to achieve both low jitter and tolerance to variations.
Solution Approach 2:
The patent implements parameter changes by selecting from multiple predetermined gain values based on current operating conditions. The control circuit modifies the VCO gain parameter to balance jitter performance and tolerance to variations, using higher gain values when temperature or voltage variations are significant and lower gain values when conditions are stable.
4Stability of the object's composition
If a conventional low-gain VCO is used with additional frequency-calibration circuit, then the manufacturing process variation is mitigated, but the circuit area and cost increase
Solution Approach 1:
The patent implements a multi-functional VCO system that combines frequency calibration and jitter reduction capabilities within a single integrated structure. The control circuit performs multiple functions including gain selection, frequency calibration, and jitter optimization, eliminating the need for separate calibration circuits and reducing overall circuit area.
Solution Approach 2:
The patent merges the frequency calibration function with the gain control mechanism. By integrating these functions into a single control system that dynamically adjusts gain based on operating conditions, the patent eliminates the need for separate calibration circuits, thereby reducing circuit area and complexity while maintaining frequency accuracy.
Data Source
AI summary
Disclosed is a voltage-controlled oscillator (VCO) capable of providing an effective high VCO gain against slow change of an input voltage caused by the variation of manufacturing processes, temperature, voltage, etc. and providing an effective low VCO gain against rapid change of the input voltage for reducing jitter. The VCO includes: an input circuit generating an input current according to an input voltage; a first current supply circuit generating a first output current according to the input current; a second current supply circuit generating a second output current according to the input current; a filter coupled to the input circuit and the second current supply circuit and configured to slow down the influence caused by the variation of the input current on the second current supply circuit; and an oscillating circuit generating an output clock according to the first output current and the second output current.