Transponder Retro-Modulation Using Zero-Impedance Load and Delay Circuits
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Solution Overview
Problem
Conventional contactless transponders face challenges in optimizing Load Modulation Amplitude (LMA) while maintaining frame synchronization, especially in varying electromagnetic field conditions, due to the need to extract a clock signal from the carrier wave, which limits impedance modulation and communication range.
Innovation Solution
A contactless communication method and transponder design that employs zero or almost zero impedance in the modulated state, using controlled delays to synchronize frame transmission, allowing for precise timing and increased LMA, thereby enhancing communication range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the carrier signal is modulated with zero or almost zero impedance in the modulated state, then the Load Modulation Amplitude (LMA) is maximized and communication range is increased, but the clock signal extraction becomes impossible during the modulated state
Solution Approach 1:
The patent applies preliminary action by measuring a duration over clock cycles before the modulated state begins, using a second delay to prepare the timing reference in advance. This allows the system to have the clock timing ready before the zero-impedance modulated state occurs, when clock extraction would be impossible. The measurement of duration over clock cycles is performed in the unmodulated state, preparing the timing information before the modulated state interrupts clock signal availability.
Solution Approach 2:
The patent uses delay circuits as intermediary elements to bridge the gap between the modulated and unmodulated states. The first delay circuit generates a delay to control the transition instant from modulated to unmodulated state, while the second delay circuit generates a delay to control the transition from unmodulated to modulated state. These delay circuits act as intermediaries that manage the timing coordination between states where clock extraction is possible and impossible.
2Manufacturing precision
If the transition instant from modulated state to unmodulated state is controlled at an instant determined by a delay, then precise frame synchronization is achieved, but the system complexity increases due to delay circuit requirements
Solution Approach 1:
The patent applies self-service by using the existing clock signal from the carrier wave to generate the timing reference for the delay circuits. The system uses its own clock signal, extracted during the unmodulated state, to control the timing of transitions. The delay circuits are controlled by measuring duration over clock cycles, allowing the system to self-regulate its timing without requiring external time references or complex synchronization mechanisms.
3Length of stationary object
If the load modulation is performed with zero or almost zero impedance, then the communication range is extended, but the impedance variation visibility from reader side may be affected by electromagnetic field conditions
Solution Approach 1:
The patent applies dynamics by making the impedance modulation adaptive rather than fixed. The system dynamically adjusts the timing of transitions between modulated and unmodulated states based on measured duration over clock cycles. The delay circuits allow the system to adapt the timing to varying electromagnetic field conditions, ensuring that the load modulation remains effective across different communication ranges and field strengths. The modulated state duration is controlled dynamically through the delay mechanism.
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 maximizes LMA, increasing the range of contactless communication by maintaining precise synchronization and adapting to different conditions, even when clock signal extraction is not possible in the modulated state.
Implementation Method 1
a passive transponder has no power supply and uses the energy transmitted by the carrier wave coming from the reader to power its integrated circuit
Implementation Method 2
The transponder then modulates the field generated by the reader, according to the information to be transmitted. The frequency of this modulation corresponds to a subcarrier of said carrier. The frequency of this sub-carrier depends on the communication protocol used and may for example be equal to 848 kHz. The modulation is performed by modifying the load connected to the terminals of the transponder antenna.
Data Source
AI summary
A contactless communication method comprises retro-modulation of a carrier signal received at the terminals of an antenna in an alternation of modulated states and unmodulated states. The modulated state comprises a modulation of a load at the terminals of the antenna at zero impedance, and the transitions from the modulated state to the unmodulated state are controlled at an instant determined by a first delay.