PLL VCO Gain Calibration Without Open-Loop Lock Loss

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Solution Overview

Problem

Conventional phase locked loop circuits face challenges in online gain calibration due to phase variations caused by manufacturing, voltage, and temperature changes, leading to unsatisfactory feedback structure adjustments and loss of clocked data, especially when switching to open loop for offline calibration.

Innovation Solution

A phase locked loop circuit with a gain calibration module that induces a frequency variation characterized by a delta function in the output frequency, allowing for online gain calibration of the voltage controlled oscillator by detecting phase errors, thereby maintaining closed-loop operation and preventing phase locking issues.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If phase locked loop circuits switch to open loop for offline calibration, then gain detection can be performed, but the phase locked loop may go out of phase and calibration cannot be completed online

Engineering Contradiction:

Improvegain detection precisionVSAvoidphase locking reliability

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent maintains the phase locked loop in closed-loop operation throughout the calibration process, ensuring continuous phase tracking and preventing loss of lock. The calibration is performed by injecting test signals and measuring phase errors while the loop remains active, eliminating the need to switch to open-loop mode and ensuring uninterrupted useful action of phase synchronization

Inventive Principle:

Principle #20Continuity of useful action

Solution Approach 2:

The patent introduces a phase error detector as an intermediary component that measures the phase difference between the reference signal and the feedback signal. This mediator enables gain calibration by providing quantitative phase error measurements without disrupting the closed-loop operation, allowing calibration data to be extracted while maintaining phase locking

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If feedback structure adjustment is used for wide frequency phase variation ranges, then some phase variations can be adjusted, but the adjustment is unsatisfactory for wide ranges

Engineering Contradiction:

Improvefrequency phase variation rangeVSAvoidphase adjustment precision

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent transitions from adjusting phase in the time domain through feedback structure modification to measuring and calibrating phase errors in the frequency domain by injecting test signals at specific frequencies. This dimensional change enables precise gain measurement across wide frequency ranges by analyzing the phase error response to frequency-varying test signals, rather than attempting direct time-domain phase adjustment

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS8368480B2Phase locked loop circuits and gain calibration methods thereof

Publication Date: 2013.02.05 MEDIATEK INC

AI summary

Phase locked loop circuits are provided, in which a phase locked loop module includes a voltage controlled oscillator to generate an oscillation signal with an output frequency according to a control voltage, and a gain calibration module triggers the phase locked loop module to induce a frequency variation characterized by a delta function in the output frequency and calculates a gain of the voltage controlled oscillator according to a phase error caused by the frequency variation in the output frequency.