Contactless Smart Card Load Modulation for Low-Distortion RF Signals
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Solution Overview
Problem
In contactless smart card systems, signal distortion occurs due to fixed load impedance in the receiving terminal, which generates noise during wireless signal transmission.
Innovation Solution
A smart card design with an antenna, load circuit, rectifier, and power generator including diodes and voltage regulators that modulate load impedance to minimize signal distortion by controlling voltage levels and impedance during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a voltage regulator with fixed load impedance is used to generate power from the electric field, then power generation is enabled, but signal distortion occurs during wireless signal transmission
Solution Approach 1:
The patent implements a switching circuit that dynamically changes the load impedance of the voltage regulator based on operation mode. In reception mode, the load impedance is set to a fixed value for stable power generation. In transmission mode, the load impedance is changed to minimize signal distortion. This dynamic adjustment resolves the contradiction between enabling power generation and maintaining signal transmission quality.
Solution Approach 2:
The patent changes the electrical parameter (load impedance) of the voltage regulator according to the operation mode. By adjusting the load impedance parameter from a fixed value to a variable value that can be optimized for different modes, the system achieves both effective power generation and minimal signal distortion during transmission.
2Stability of the object's composition
If fixed load impedance is used in the voltage regulator, then power generation from electric field is stable, but noise is generated during wireless signal transmission
Solution Approach 1:
The switching circuit dynamically adjusts the load impedance of the voltage regulator based on operation mode. During reception mode, fixed load impedance ensures stable power generation. During transmission mode, the load impedance is modified to reduce noise generation. This dynamic adaptation resolves the contradiction between power generation stability and noise reduction.
3Reliability
If load impedance is modulated for signal transmission, then signal distortion is reduced, but power generation efficiency decreases
Solution Approach 1:
The system periodically switches between reception mode and transmission mode, with the switching circuit adjusting the load impedance accordingly. During reception mode, fixed impedance maximizes power generation efficiency. During transmission mode, modified impedance optimizes signal quality. This periodic switching resolves the contradiction by applying different impedance settings at different times based on operational requirements.
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
The solution reduces signal distortion and noise interference, ensuring stable wireless signal transmission by maintaining constant voltage levels and adjusting impedance according to transmission mode.
Implementation Method 1
an antenna configured to transmit and receive at least one radio signal
Implementation Method 2
a rectifier configured to rectify the at least one radio signal received through the antenna
Data Source
AI summary
A smart card may include: an antenna configured to receive at least one radio signal; a load circuit that is connected to both ends of the antenna; a rectifier configured to rectify the at least one radio signal received through the antenna, and provide the rectified signal to an output terminal; and a power generator including a voltage regulator, a first diode, and a second diode, the voltage regulator configured to provide an internal voltage, the first diode and the second diode connected in series between the output terminal of the rectifier and a first node, and the first node is configured to receive the internal voltage during a first mode of the smart card, the first mode being a mode during which a load of the load circuit is modulated.