RFID Carrier Phase Modulation for High Bit Rates and Stable Power Feed
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Solution Overview
Problem
Current RFID systems face challenges in increasing bit rates beyond the Mb/s range while maintaining remote power feed and compliance with European recommendations, due to limitations in channel bandwidth and phase modulation-induced spurious amplitude modulations.
Innovation Solution
A phase modulation method where a phase jump between symbols is spread over a first part of the symbol time, with the establishing of the phase jump completed in that part and constant periods during the second part, to minimize undesirable effects and maintain remote power feed and compliance with standards.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If phase modulation is used to increase bit rates beyond Mb/s, then data transmission speed is improved, but spurious amplitude modulations are generated causing communication failures
Solution Approach 1:
The phase jump is segmented into multiple smaller phase jumps applied to individual carrier cycles within the symbol. Instead of applying the total phase jump instantaneously, it is distributed across several cycles (e.g., if total phase jump is Δφ and symbol time is Ts with N cycles, each cycle receives a phase jump of approximately Δφ/N). This segmentation reduces the amplitude of spurious modulations while maintaining the overall phase modulation effect for data transmission.
Solution Approach 2:
The phase jump is prepared and applied gradually at the beginning of the symbol time rather than instantaneously. The first part of the symbol time is dedicated to establishing the phase jump in a controlled manner, preventing sudden transitions that would generate harmful spurious amplitude modulations. This preliminary action ensures that the phase modulation occurs smoothly without disrupting the carrier amplitude.
2Productivity
If channel bandwidth is widened to increase bit rates, then data transmission speed is improved, but remote power feed capability deteriorates
Solution Approach 1:
The invention changes the temporal distribution parameter of the phase jump within the symbol structure. By confining the phase jump establishment to the first part of the symbol time and maintaining constant carrier periods in the second part, the effective bandwidth utilization is optimized without requiring excessive bandwidth expansion. This parameter adjustment allows achieving higher bit rates through more efficient use of the available bandwidth while preserving the remote power feed function.
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 allows for higher data rates while maintaining remote power feed and compliance with European recommendations, reducing communication failures and optimizing data transmission.
Implementation Method 1
The reader, considered as a base station, generates a carrier wave (short range alternating magnetic field) which serves to power the contactless cards in proximity to the antenna of the reader. This is referred to as remote power feed.
Implementation Method 2
This antenna may be modeled electrically in the form of a resonant circuit of R, L, C type characterized by a center frequency fc, a quality coefficient Q and having a limited bandwidth BP. fc=1/(2π√{square root over (LC)})
Data Source
AI summary
A method for phase modulation of a carrier signal from a transmitter to a contactless transponder in which data is coded as consecutive symbols, each corresponding to a predefined number of carrier cycles, and in which a symbol time is at least two cycles of the carrier signal includes, at the transmitter, spreading a phase jump of a symbol in relation to a preceding symbol over a first part of the symbol time. The establishment of the phase jump is completed in the first part of the symbol time. The periods of the cycles are constant during a second part of the symbol time.