RFID Transponder Clock Recovery via Current Sensing
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Solution Overview
Problem
RFID transponders face challenges in maintaining proper clock recovery during modulation, as the residual carrier amplitude is insufficient, limiting the strength of the return link, and the use of a Phase-Locked Loop (PLL) increases current consumption, reducing the operating range.
Innovation Solution
Incorporating a current sensor to sense the current in the modulation path and using it for clock recovery instead of or in addition to the input voltage, allowing for stable clock recovery during modulation, and switching between sensed current and residual carrier based on modulation state.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Phase-Locked Loop (PLL) is used for clock recovery, then clock recovery accuracy is improved, but current consumption increases
Solution Approach 1:
The patent extracts the clock recovery function from the traditional PLL approach and implements it using a simpler circuit that utilizes the existing modulation path and current sensor. This extraction eliminates the need for complex PLL components while maintaining clock recovery capability, thereby reducing current consumption.
Solution Approach 2:
The patent replaces the mechanical/electronic PLL system with an electrical solution using current sensing and voltage-based clock recovery. This substitution uses the current already flowing through the modulation path during RFID communication to derive the clock signal, eliminating the need for separate PLL hardware and reducing power consumption.
2Measurement precision
If residual carrier amplitude is used for clock recovery during modulation, then clock recovery is possible, but the strength of the return link is limited
Solution Approach 1:
The patent introduces a current sensor as an intermediary element that measures the current in the modulation path. This current information serves as a mediator to enable accurate clock recovery during modulation without relying on the residual carrier amplitude, thereby maintaining return link strength while enabling proper clock recovery.
Solution Approach 2:
The patent changes the parameter used for clock recovery from residual carrier amplitude to sensed current. By switching to current-based clock recovery during modulation, the system can maintain strong return link while achieving accurate clock recovery, as the current signal preserves the modulation information needed for clock extraction.
3Reliability
If modulation strength is increased to enhance return link, then return link strength is improved, but clock recovery becomes difficult due to insufficient residual carrier
Solution Approach 1:
The patent implements feedback by continuously sensing the current in the modulation path and using this information to maintain clock recovery. The current sensor provides feedback about the modulation state, enabling the system to adapt and maintain accurate clock recovery even when modulation strength is increased to enhance return link performance.
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 enhances the strength of the return link by enabling proper clock recovery during strong modulation without limiting modulation strength and reduces current consumption by avoiding the need for a PLL.
Implementation Method 1
a current sensor (104) which is configured to sense a current in a modulation path of the RFID transponder
Data Source
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AI summary
In accordance with a first aspect of the present disclosure, a radio frequency identification (RFID) transponder is provided, comprising a modulator, a current sensor and a clock recovery circuit, wherein: the modulator is configured to modulate an unmodulated carrier signal received from an external RFID reader; the current sensor is configured to sense a current that flows through one or more transistors comprised in the modulator; and the clock recovery circuit is configured to recover a clock signal using the current sensed by the current sensor. In accordance with a second aspect of the present disclosure, a corresponding method of operating a radio frequency identification (RFID) transponder is conceived.