Two-Input PLL Polar Modulation With Digital Feedback Compensation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional direct and polar modulation transmitters using fractional-N phase locked loops (PLL) suffer from distortion due to low pass filtering issues and component mismatches, leading to inefficient power consumption and increased complexity in mobile multimedia applications.
Innovation Solution
A method and system employing a two-input PLL with digital feedback compensation, generating digital signals Wn and Vn to adaptively control the PLL, which compensates for non-idealities and bandwidth variations, thereby reducing distortion and improving signal transmission fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional fractional-N PLL designs are used for direct and polar modulation, then the transmitter can be implemented with standard IC manufacturing processes, but distortion occurs due to low pass filtering issues and component mismatches
Solution Approach 1:
The patent introduces a digital feedback equalizer that receives the output signal from the PLL and feeds back correction signals to compensate for distortion. This feedback mechanism continuously adjusts the system to counteract the low pass filtering effects and component mismatches, maintaining signal fidelity while using standard IC manufacturing processes
Solution Approach 2:
The patent employs digital equalization parameters that can be dynamically adjusted to compensate for PLL distortion characteristics. By changing the equalizer parameters based on measured or predicted distortion conditions, the system maintains high signal fidelity without requiring precision manufacturing tolerances
2Adaptability or versatility
If analog control circuitry is used to control analog PLL circuitry, then analog component values can be tuned to control component behavior, but mismatches between components in the analog PLL circuitry and components in the analog control circuitry occur
Solution Approach 1:
The patent replaces the analog control circuitry with a digital control system that interfaces with the analog PLL. This substitution eliminates the component matching problems between analog circuits by using digital logic and algorithms to achieve the same control functionality with higher precision and without physical component mismatches
Solution Approach 2:
The patent introduces a digital-to-analog converter and control interface as an intermediary between the digital control logic and the analog PLL circuitry. This intermediary layer allows precise digital control of analog parameters without direct analog-analog component matching, resolving the mismatch issue while maintaining tunability
3Speed
If the cutoff frequency of the low pass filter is within the range of frequencies utilized by the transmitter, then the PLL can operate at standard frequencies, but the input signal becomes distorted
Solution Approach 1:
The digital feedback equalizer detects signal distortion caused by the low pass filter and generates correction signals that compensate for the frequency-dependent attenuation and phase shift. This allows the PLL to operate at standard frequencies while the equalizer restores the distorted signal components
Solution Approach 2:
The patent applies preliminary equalization to the input signal before it enters the PLL, or applies post-equalization to the output signal, to pre-compensate or compensate for the anticipated low pass filtering effects. This preliminary anti-action counteracts the distortion before it degrades signal quality
Data Source
AI summary
Aspects of a method and system for direct and polar modulation using a two input PLL are presented. Aspects of the system may include generating digital signals Wn and Vn from an input data signal Un and a feedback signal Yn. The generated digital signals Wn and Vn combined may carry the information content of Un while they compensate the non-idealities of the two-input analog phase locked loop (PLL). The digital signal Wn, which may be scaled appropriately in frequency, and the digital signal Vn may be provided as inputs to the PLL. The feedback signal Yn may be a digital signal that may correspond to the analog feedback signal Pt that may be generated by the PLL. Accordingly, the PLL may be adaptively controlled via the digital signals Wn and Vn for properly transmitting the input data signal Un.