Negative Modulation Contactless Transponder for Small Antennas
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Solution Overview
Problem
Current radio-frequency communication technologies, such as ISO/IEC 14443 and NFC, face challenges in achieving effective communication distances due to the small size of contactless objects like micro-SD cards, which have limited antenna surface area, leading to insufficient coupling with readers and restricted modulation amplitude, limiting communication range and efficiency.
Innovation Solution
The method involves negative modulation of the carrier frequency by a contactless transponder, increasing the amplitude of sidebands up to 200% of the carrier frequency, allowing for greater communication distances and reduced antenna size while maintaining compliance with standards, by applying a modulation rate greater than 100% and generating sidebands independently of the reader.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If retro-modulation of reader's electromagnetic field is used to communicate, then communication can be established according to ISO/IEC standards, but the small antenna surface area of micro-SD cards results in insufficient coupling with readers and restricted modulation amplitude
Solution Approach 1:
The patent changes the modulation parameter from conventional amplitude modulation (0-100% modulation rate) to negative modulation (greater than 100% modulation rate). This parameter change allows the transponder to generate sidebands with amplitude exceeding the carrier frequency amplitude, thereby compensating for the insufficient coupling caused by small antenna surface area and achieving reliable communication.
Solution Approach 2:
The patent inverts the conventional modulation approach by using negative modulation where the modulation rate exceeds 100%. Instead of the transponder merely modulating the reader's field within limited amplitude ranges, the transponder now generates sidebands that are stronger than the carrier, effectively reversing the traditional amplitude relationship and overcoming the coupling limitation.
2Power
If conventional amplitude modulation with modulation rate between 0 and 100% is used, then sidebands are generated for communication, but the modulation amplitude is restricted and communication distance is limited
Solution Approach 1:
The patent fundamentally changes the modulation rate parameter from the conventional 0-100% range to greater than 100% (negative modulation). This parameter change directly increases the sideband amplitude beyond the carrier amplitude, thereby extending the effective communication distance without requiring larger antennas or higher power transmission.
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 significantly enhances communication distances between readers and transponders, reduces the required antenna size, and minimizes current consumption, while ensuring compatibility with existing standards, particularly benefiting micro-SD cards and other small contactless devices.
Implementation Method 1
a radio-frequency transponder object communicates by modulation of the amplitude of a carrier frequency
Implementation Method 2
Radio-frequency communication is in principle of short range and effected by lower electromagnetic induction and coupling with a range of around 0.01 or even approximately 1 m
Data Source
AI summary
The present invention concerns a method of radio-frequency communication between a contactless transponder and a reader, in which at least one sideband of the carrier frequency is used for communicating a response from the transponder by modulation of the amplitude of this carrier frequency. The method is distinguished in that the modulation at least partly applies a modulation level greater than 100%, which causes a negative modulation. The invention also concerns a corresponding communication circuit.