DCO Gradient Factor Identification for Low-EVM PLL Modulation
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Solution Overview
Problem
In mobile radio systems, determining the gradient factor of a digitally controlled oscillator (DCO) is challenging, especially during operation, as inaccuracies can lead to inadmissible distortions in modulated output signals, particularly in systems like UMTS where breaks for oscillator gradient ascertainment are not available, complicating the process and increasing error vector magnitude (EVM).
Innovation Solution
An arrangement comprising a data alignment device and an identification device is used to determine the gradient factor by conditioning modulation signals, phase error signals, and oscillator control words to derive necessary magnitudes, allowing for accurate ascertainment of the gradient factor during operation through a data alignment process and identification device adaptation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the gradient factor KDCO is assumed to be at an optimum, then the frequency change of the output signal is accurate and sudden, but if the gradient factor is incorrect, then inadmissible distortions arise and error vector magnitude increases
Solution Approach 1:
The patent implements a feedback mechanism where the actual frequency output of the DCO is measured and compared with the expected frequency based on the control word. The difference (error signal) is used to continuously adapt and refine the gradient factor KDCO, ensuring that the oscillator's frequency response remains accurate despite variations in operating conditions such as temperature or process deviations.
Solution Approach 2:
The patent dynamically adjusts the gradient factor KDCO as a variable parameter based on measured performance. Instead of using a fixed assumed value, the system changes the KDCO parameter in real-time to match the actual characteristics of the DCO, thereby maintaining optimal frequency accuracy and minimizing distortion under varying operating conditions.
2Measurement precision
If breaks are available for oscillator gradient ascertainment, then the gradient factor can be determined accurately, but in continuous modulation systems like UMTS, breaks are not available making determination challenging
Solution Approach 1:
The patent enables continuous determination of the gradient factor during ongoing modulation operations without requiring system pauses or breaks. The measurement and adaptation process runs continuously alongside normal signal generation, allowing the system to maintain accurate gradient knowledge even in continuous modulation schemes like UMTS where traditional measurement breaks are unavailable.
Solution Approach 2:
The system performs self-diagnosis and self-calibration by using its own output signal to determine its gradient factor. The DCO's frequency output is fed back into the measurement apparatus, allowing the system to automatically characterize itself without external intervention or system interruptions, thereby simplifying operation in continuous modulation modes.
3Reliability
If the gradient factor is determined during operation, then continuous modulation systems can maintain accuracy, but the process becomes more complex without available breaks
Solution Approach 1:
The patent divides the gradient determination process into distinct functional modules: a data alignment device that conditions and synchronizes measurement data with control words, and an identification device that extracts the gradient factor from aligned data. This segmentation allows each module to be optimized independently and simplifies the overall implementation by breaking down the complex determination process into manageable, modular stages.
Solution Approach 2:
The patent introduces a data alignment device as an intermediary component between the DCO output and the gradient analysis function. This intermediary conditions the raw frequency data, aligns it with the corresponding control words, and prepares it for gradient extraction, thereby simplifying the identification process and enabling accurate in-operation determination without excessive complexity.
Data Source
AI summary
An arrangement for determining a gradient factor for a digitally controlled oscillator has a data alignment device and an identification device. The data alignment device can be supplied a modulation signal, a phase error signal and an oscillator control word. The data alignment device is configured to output a modulation setting word based on the modulation signal, output a time interval magnitude based on the phase error signal and a reference interval, and output an oscillator modulation word based on the oscillator control word. The identification device is configured to adapt and output the gradient factor based on the modulation setting word, the time interval magnitude and the oscillator modulation word.