Battery-Free RF Transmitter Using Relative Motion Charge Induction
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Solution Overview
Problem
Current energy harvesting technologies, such as those using electrets, face challenges in efficiently converting mechanical movement into electromagnetic signals without the need for external power sources or batteries, particularly for applications requiring low-cost communication and tagging.
Innovation Solution
A device comprising a conductive element and an inducer, movable relative to each other, which induces and discharges charge through a transmission circuit to generate and transmit electromagnetic signals, leveraging the movement to produce RF signals without drawing energy from the electret.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If energy harvesting uses electrets to convert mechanical movement into electricity, then energy can be captured from small movements, but the system requires external power sources or batteries which increases device complexity and cost
Solution Approach 1:
The device uses its own movement to generate the electromagnetic signals it transmits. The conductive element moves relative to the electret during normal device operation, and this movement directly generates the charging/discharging cycles that produce RF signals, eliminating the need for separate power sources
Solution Approach 2:
The patent combines the energy harvesting function with the signal transmission function into a single integrated system. The same mechanical movement that operates the device also generates the electromagnetic signals for communication, merging two separate functions into one unified mechanism
2Use of energy by moving object
If the conductive element and inducer are positioned close together to induce charge, then charging efficiency improves, but the device structure becomes more constrained and complex
Solution Approach 1:
The system uses dynamic relative movement between the conductive element and electret instead of fixed positioning. The elements move closer during charging phases and separate during discharging phases, allowing efficient charge induction without permanent structural constraints
Solution Approach 2:
The charging and discharging process occurs in periodic cycles as the conductive element alternately approaches and recedes from the electret. This periodic movement creates repeated charging/discharging events that generate continuous RF signals without requiring complex positioning mechanisms
3Device complexity
If the device transmits electromagnetic signals using movement-induced charge, then battery-free operation is achieved, but the signal transmission range and power may be limited
Solution Approach 1:
The system varies the movement parameters (amplitude, frequency, velocity) of the conductive element relative to the electret to optimize signal transmission power. Different movement characteristics produce different charge induction rates, allowing adjustment of transmitted signal strength without changing the fundamental battery-free mechanism
Solution Approach 2:
The patent utilizes vibrational movement of the conductive element relative to the electret to enhance charge induction efficiency. By incorporating vibrational motion into the relative movement, the system can generate stronger and more consistent electromagnetic signals while maintaining battery-free 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
Enables low-cost, battery-free communication and tagging by deriving all energy for signal generation from device movement, suitable for applications like emergency beacons, telemetry, and position fixing, with potential operation at RF and microwave frequencies.
Implementation Method 1
at least one inducer, for inducing charge in said conductive element
Implementation Method 2
the conductive element is arranged to couple with the transmission circuit, in said first position and/or said second position, such that charging and/or discharging of said conductive element causes the transmission circuit to generate and transmit an electromagnetic signal
Data Source
AI summary
A device for the transmission of electromagnetic signals, the device comprising: a conductive element at least one inducer, for inducing charge in said conductive element; a transmission circuit, for generation and transmission of electromagnetic signals; wherein said conductive element and said at least one inducer are movable, with respect to each other, between a plurality of relative positions; in a first position of said relative positions, said at least one inducer is arranged to induce a charge in said conductive element; in a second position of said relative positions, said conductive element is arranged to discharge; the conductive element is arranged to couple with the transmission circuit, in said first position and/or said second position, such that charging and/or discharging of said conductive element causes the transmission circuit to generate and transmit an electromagnetic signal; and the device is arranged such that movement of said device causes relative movement of said conductive element and said at least one inducer between said plurality of relative positions.