MIMO Base Station Waveform Control for RFID Energy Harvesting
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Solution Overview
Problem
Existing wireless power transfer systems for passive RFID tags face limitations in increasing incident power due to regulatory constraints and inefficiencies in multipath environments, which affect energy harvesting and communication efficiency.
Innovation Solution
A method and apparatus for real-time wireless power transfer control using MIMO base stations that emit power-optimized waveforms, adjusted through a closed-loop feedback control algorithm based on measurements of backscattered signals to compensate for channel impairments and ensure optimal energy delivery to RFID tags.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If transmit power of interrogators is increased to boost energy flow to transponders, then harvestable energy increases, but regulatory constraints are violated and system efficiency decreases in multipath environments
Solution Approach 1:
The system changes the parameters of the transmitted waveform from traditional continuous wave to power-optimized waveforms with specific amplitude and phase characteristics across multiple subcarriers. This allows the system to deliver higher peak power to transponders without increasing average transmit power, thereby increasing harvestable energy while maintaining regulatory compliance and improving system efficiency in multipath environments.
Solution Approach 2:
The system implements closed-loop feedback control by measuring backscattered signals from transponders and using this information to adjust and optimize the transmitted waveforms in real-time. This feedback mechanism enables the system to adapt to changing channel conditions and transponder states, maximizing energy transfer efficiency without violating regulatory power constraints.
2Device complexity
If traditional continuous wave RF signals are used for power delivery, then system simplicity is maintained, but energy harvesting efficiency is limited especially at low incident power levels
Solution Approach 1:
The system transforms the simple continuous wave signal into complex power-optimized waveforms that incorporate multiple frequency components with specifically optimized amplitude and phase relationships. These waveforms exploit the nonlinear characteristics of rectifier circuits in energy harvesters to achieve significantly improved harvesting efficiency, particularly at low incident power levels close to the harvesting threshold.
3Productivity
If frequency allocation planning is used to increase information throughput, then spectrum sharing is improved, but selective manipulation of power delivered to individual transponders is precluded
Solution Approach 1:
The system segments the power delivery to individual transponders by using spatially selective beamforming and individualized power-optimized waveforms for each transponder. This allows independent control of power levels delivered to each transponder while maintaining frequency sharing among multiple readers, enabling both high information throughput and selective power manipulation.
Solution Approach 2:
The system applies local quality by tailoring the waveform characteristics (amplitude, phase, frequency components) specifically for each transponder's location and channel conditions. This localized optimization allows selective power delivery to individual transponders while maintaining overall system throughput through coordinated multi-reader operation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enhances the efficiency of RF energy harvesting by dynamically adjusting waveforms to counteract channel distortions and interference, thereby increasing the harvestable energy available to tags while maintaining regulatory compliance.
Implementation Method 1
the sensor tag by modulated scattering of the first waveform as incident upon the sensor tag
Data Source
AI summary
A method and apparatus is disclosed herein for real-time wireless power transfer control. In one embodiment, a system comprises: an RF-energy harvesting sensor tag operable to generate a first backscatter signal and at least one base station operable to deliver RF power to the sensor tag by emitting a first waveform comprising a plurality of subcarriers, wherein the first backscatter signal is generated by the sensor tag by modulated scattering of the first waveform as incident upon the sensor tag, and further wherein the at least one base station subsequently emits a second waveform determined at least in part by a closed-loop feedback control algorithm responsive to measurements of the first backscatter signal.