ADPLL Frequency Generator With LMS DCO Gain Tracking
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional analog phase-locked loops (PLLs) are prone to errors and require complex recalibration during frequency hopping, leading to inefficiencies in digital radio transmitters and receivers, while existing digital PLL calibration techniques are inadequate for precise gain tracking of digitally controlled oscillators (DCOs).
Innovation Solution
An all-digital phase-locked loop (ADPLL) with a Least Mean Squares (LMS)-based calibration unit iteratively calibrates the DCO gain using a filtered phase error, allowing for precise estimation and tracking of the DCO normalization value, enabling fast and accurate frequency hopping without repeated close-loop locking processes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional analog PLL is used, then frequency generation is achieved, but errors and error propagation occur due to analog operations and elements
Solution Approach 1:
The patent replaces analog PLL operations with digital PLL operations, substituting analog elements (VCO, analog phase detector) with digital equivalents (DCO, digital phase detector). This digital substitution eliminates analog errors and error propagation while maintaining frequency generation functionality through iterative DCO gain calibration using LMS algorithm.
2Productivity
If conventional PLL frequency hopping is performed, then channel switching is achieved, but complex recalibration is required leading to inefficiency
Solution Approach 1:
The patent performs preliminary DCO gain calibration before frequency hopping operations. By pre-calibrating the DCO gain using the LMS algorithm and storing the calibration data, the system eliminates the need for complex recalibration during frequency hopping, enabling fast channel switching without repeated close-loop locking processes.
Solution Approach 2:
The system uses its own phase error signal and operating conditions to perform self-calibration of the DCO gain. The LMS algorithm utilizes the existing phase error and control word information to iteratively adjust and optimize the DCO gain, making the calibration process self-contained and eliminating external calibration requirements.
3Measurement precision
If DCO gain calibration is performed, then frequency accuracy is improved, but iterative calibration process requires time and resources
Solution Approach 1:
The patent implements continuous DCO gain calibration using the LMS algorithm that operates iteratively during normal operation. Rather than performing discrete calibration steps, the system continuously adjusts the DCO gain using the ongoing phase error signal, achieving high accuracy without interrupting the frequency generation process or requiring separate calibration phases.
Data Source
AI summary
A frequency generator is disclosed. The frequency generator is for generating an oscillator clock according to a reference clock, and the frequency generator is used in a frequency hopping system that switches a carrier frequency among a plurality of channels, and the carrier frequency further carries a modulation frequency for data transmission. The frequency generator includes: a frequency hopping and modulation control unit, arranged for generating a current channel according to a channel hopping sequence and a frequency command word (FCW) based on the reference clock, a digital-controlled oscillator (DCO), arranged for to generating the oscillator clock according to an oscillator tuning word (OTW) obtained according to the estimated DCO normalization value. An associated method is also disclosed.