Semi-Passive Backscatter Tag Impedance Modulation
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Solution Overview
Problem
Conventional backscatter communication systems, such as RFID, face limitations in data throughput and range due to energy harvesting from electromagnetic energy, which slows down data rates and reduces read range, especially for fully passive tags.
Innovation Solution
Integration of semi-passive backscatter tags into mobile devices powered by the device's battery, allowing impedance modulation of the antenna to encode data without energy harvesting from electromagnetic energy, optimizing signal-to-noise ratio and increasing data throughput by using higher clock rates and advanced modulation techniques like QAM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If energy harvesting from electromagnetic energy is used in passive tags, then the tag can operate without a battery, but the data rate is slowed down and read range is reduced
Solution Approach 1:
The system dynamically switches between two operational modes: passive mode for energy harvesting and semi-passive mode for high-speed communication. The tag can transition between these modes based on communication requirements, allowing optimization of both energy efficiency and data rate depending on the operational context.
Solution Approach 2:
The patent changes the power supply parameter from purely passive (energy harvesting only) to semi-passive (battery + energy harvesting). This parameter change enables the tag to operate at higher clock rates and use advanced modulation techniques like QAM, thereby resolving the contradiction between energy autonomy and data rate.
2Use of energy by moving object
If energy harvesting from electromagnetic energy is used in passive tags, then the tag can operate without a battery, but the read range is reduced
Solution Approach 1:
The system dynamically switches between passive and semi-passive operational modes. When extended read range is required, the tag can utilize its battery power in semi-passive mode, overcoming the read range limitation imposed by pure energy harvesting in passive mode.
Solution Approach 2:
By changing the power supply parameter to include battery assistance, the tag gains additional energy resources that directly extend the read range. The battery provides supplemental power that compensates for the limited energy available from harvesting alone, thereby resolving the read range contradiction.
3Productivity
If higher clock rates and advanced modulation techniques are used, then data throughput is increased, but power consumption increases
Solution Approach 1:
The system dynamically adjusts its operational mode based on communication requirements. When high data throughput is needed, the tag switches to semi-passive mode with battery power to support higher clock rates and advanced modulation. When lower data rates suffice, it can operate in passive mode to conserve battery life, thus dynamically balancing throughput and power consumption.
Solution Approach 2:
The patent changes the power supply parameter to enable the tag to support higher operating frequencies and more complex modulation schemes. By adding battery power to the energy harvesting, the tag can sustain the higher power consumption required for high-throughput operations without being permanently constrained by energy harvesting limitations.
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 enables high-bandwidth, low-power backscatter communication with data rates up to 100 Mbps over short ranges, improving data throughput and reducing bit rate errors while maintaining battery life, and is backward compatible with existing RFID protocols.
Implementation Method 1
a tag reflects a portion of the electromagnetic energy back to the base station in order to communicate data to the reader
Implementation Method 2
modulation circuitry to modulate an impedance of an antenna of the mobile device for communicating with an RFID base station
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Backscatter communication includes receiving electromagnetic energy from a base station and encoding first data and second data. The first data is encoded at a first frequency by adjusting a radar cross-section of a device to modulate the electromagnetic energy reflected back to the base station. The second data is encoded at a second frequency by limiting the adjusting of the plurality of radar cross-sections to either a first subset or a second subset of the plurality of radar cross-sections for a length of time. The second frequency is lower than the first frequency.