PLL Error-Signal Scaling for Frequency-Independent Gain Calibration
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Solution Overview
Problem
Phase locked loops in wireless communication equipment face performance variations due to changes in oscillator gain, which affects the modulation of carrier signals, and existing calibration methods are either invasive or frequency-dependent.
Innovation Solution
An apparatus and method that utilize a scaling controller and sign detector to adjust the modulation signal based on the error signal, ensuring the modulation and phase signals have the same sign, thereby calibrating the oscillator gain independently of spectral content and allowing for continuous operation without dedicated calibration periods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the oscillator gain is increased to amplify high frequencies of the modulation signal, then the amplification of high frequencies is improved, but the oscillator gain becomes too high causing excessive amplification of high frequencies
Solution Approach 1:
The patent dynamically adjusts the scaling factor of the modulation signal based on the detected sign of the error signal. By changing the parameter (scaling factor) in response to error signal conditions, the system compensates for oscillator gain variations and maintains accurate modulation across different frequency ranges without requiring fixed high gain settings.
2Power
If the oscillator gain is decreased to reduce amplification of high frequencies, then the amplification of high frequencies is reduced, but the oscillator gain becomes too low causing insufficient amplification of high frequencies
Solution Approach 1:
The system uses feedback from the error signal to continuously monitor and adjust the modulation signal scaling. The feedback mechanism detects when oscillator gain deviates from ideal values and automatically corrects the modulation signal accordingly, ensuring reliable modulation accuracy regardless of whether the oscillator gain is too high or too low.
3Reliability
If calibration is performed by scaling the modulation signal applied to the input of the oscillator, then the oscillator gain variations are compensated, but the control of the degree of scaling becomes complex
Solution Approach 1:
Instead of implementing a complex global scaling control mechanism, the patent applies local quality adjustment by scaling the modulation signal based on the local condition of the error signal sign. This localized approach simplifies the control mechanism while effectively compensating for oscillator gain variations.
Solution Approach 2:
The patent changes the scaling parameter dynamically based on the error signal characteristics rather than using a fixed complex control algorithm. This parameter change approach maintains reliability while reducing device complexity by using a straightforward conditional scaling mechanism.
4Reliability
If existing calibration methods are used, then oscillator gain calibration is achieved, but the calibration is frequency-dependent or requires dedicated calibration periods
Solution Approach 1:
The patent implements a universal calibration approach that works across different frequency ranges and communication standards. The method uses the error signal from normal operation to perform calibration, making the system adaptable to various frequencies and standards without requiring frequency-specific calibration procedures or dedicated calibration periods.
Solution Approach 2:
The calibration process occurs continuously during normal operation rather than requiring dedicated calibration periods. The useful action of error signal processing is continuously performed, and this same signal is used for both loop control and oscillator gain calibration, enabling uninterrupted operation across all frequency ranges.
Data Source
AI summary
A method for controlling a modulation signal for modulating a phase locked loop. A scaling control signal for scaling the modulation signal is generated using the error signal of the phase locked loop. The scaling control signal is adjusted when the modulation signal and the phase of the modulation signal have the same sign.