LC-Tank PLL Drift Correction Without Kvco Noise Penalty
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Solution Overview
Problem
Phase-locked loops struggle to handle large frequency drifts in voltage-controlled oscillators (VCOs) while maintaining low Kvco and avoiding noise or discontinuities in the output signal, especially due to temperature and environmental changes.
Innovation Solution
A phase-locked loop design that adjusts the capacitance of the LC tank circuit in incremental units using frequency adjustment control lines, with control signals ramped over a period greater than the phase-locked loop's response time to gradually correct frequency drifts, thereby extending the drift range without introducing noise or discontinuities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the Kvco of the VCO is increased to cover the expected frequency drift over an operational temperature range, then the frequency drift correction capability is improved, but the phase noise performance deteriorates
Solution Approach 1:
The patent segments the frequency correction function into two distinct mechanisms: a coarse correction mechanism using discrete capacitor bank units to handle large frequency drifts, and a fine correction mechanism using a continuously tunable varactor to handle small frequency adjustments. This segmentation allows the system to achieve large frequency drift correction capability without requiring a high Kvco, thereby avoiding the phase noise penalty that would result from increasing the varactor's capacitance range.
2Adaptability or versatility
If the frequency is adjusted by switching in or out discrete units of capacitance, then the frequency adjustment range is improved, but an instantaneous frequency error is introduced
Solution Approach 1:
The patent applies preliminary action by having the discrete capacitor bank units positioned and switched in advance to bring the VCO frequency close to the target frequency before the continuous varactor takes over for fine tuning. This preliminary coarse adjustment reduces the frequency error to a small range that the varactor can correct smoothly, preventing instantaneous frequency errors while maintaining a wide adjustment range.
3Use of energy by moving object
If the control signal range is reduced due to lower supply voltage, then the power consumption is reduced, but the frequency adjustment range deteriorates
Solution Approach 1:
The patent segments the frequency adjustment function into coarse and fine components, where the discrete capacitor bank handles the bulk of the frequency adjustment range requirement. This allows the continuous varactor to operate with a smaller control signal range suitable for low supply voltage conditions, thereby maintaining low power consumption while still achieving a wide overall frequency adjustment range through the combination of both mechanisms.
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
This approach allows for effective correction of large frequency drifts in VCOs within the phase-locked loop, maintaining a low Kvco and ensuring continuous, stable output signal frequency, thus enhancing the loop's frequency stability and performance.
Implementation Method 1
The value of the capacitance can be changed by either adjusting the value of a varactor, or by adjusting the number of discrete capacitor bank units connecting to the tank circuit
Data Source
AI summary
A phase-locked loop that supports a large frequency drift capability, yet maintains a low Kvco, and does not introduce noise or discontinuities in the frequency of the generated phase-locked loop output signal. The phase-locked loop may include a VCO with an LC tank circuit, the capacitance of which may be adjusted in incremental units. By gradually adjusting a control signal applied to a selected VCO LC tank circuit frequency adjustment control line, e.g., in a continuous ramped function, or time-averaged ramped function, from LOW-to-HIGH or from HIGH-to-LOW, over a period of time that is greater than the response time of the phase-locked loop, a frequency range supported by the VCO may be shifted to either a higher frequency range or a lower frequency range, as needed, to accommodate environmentally induced frequency drift in the VCO, without introducing noise or discontinuities in the frequency of the generated phase-locked loop output signal.