Active Receiver Switch Circuit for Dual-Mode RFID Tags
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Solution Overview
Problem
Traditional RFID tags with passive transmission capabilities lack the ability to integrate both passive and active transmission modes in a single tag architecture, limiting their versatility and efficiency in communication with external readers, especially in applications requiring both back-modulation types.
Innovation Solution
The proposed RFID tag architecture incorporates an active receiver switch circuit and modulation detection circuit, which compares antenna input signals, limits voltage, and generates demodulation signals for both 10% and 100% amplitude modulations, enabling efficient active and passive back-modulations without automatic gain control or DLL, allowing integration with passive frontends.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional passive RFID tag architecture is used, then the tag can operate with power-by-field, but it cannot integrate active transmission capability
Solution Approach 1:
The patent combines passive and active transmission capabilities into a single RFID tag architecture. The active receiver circuit is integrated with the passive power-by-field frontend, allowing the tag to function in both passive back-modulation mode (using rectifier 103 and LDO 104) and active back-modulation mode (using active receiver 5 and modulation detection circuit 12), thereby achieving versatility without requiring separate tag designs.
Solution Approach 2:
The RFID tag is designed with multi-functional capability to support both passive and active transmission modes. The system can automatically switch between 100% ASK modulation (passive) and 10% ASK modulation (active) based on the presence of an active receiver signal, making the tag universally compatible with different reader types and communication protocols.
2Adaptability or versatility
If active receiver is added to enable active back-modulation, then communication versatility improves, but device complexity increases
Solution Approach 1:
The tag architecture is segmented into distinct functional blocks: power-by-field circuitry (rectifier 103, LDO 104), active receiver (5), modulation detection circuit (12), and antenna interface. This segmentation allows independent optimization of each subsystem and simplifies the integration process, as each block can be designed and tested separately before being combined into the complete tag.
Solution Approach 2:
The modulation detection circuit (12) acts as an intermediary between the antenna input and the back-modulation output stages. It detects the modulation type (100% or 10% ASK) and controls the switching between passive and active transmission modes, thereby managing the complexity of integrating both modes without requiring complex control logic throughout the entire system.
3Productivity
If both passive and active transmission capabilities are integrated, then communication efficiency improves, but manufacturing complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the RF signal (modulation depth, frequency) to distinguish between passive and active modes. The modulation detection circuit monitors these parameters and automatically adjusts the tag's transmission behavior accordingly. This parameter-based control approach simplifies manufacturing compared to hardware switching mechanisms, as it requires only signal processing rather than complex mechanical or electronic switching components.
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 architecture enables efficient communication with both passive and active back-modulations, reducing costs and allowing the tag to adapt to existing waveforms, making it suitable for applications requiring both modes, including small antenna systems and mobile communication.
Implementation Method 1
RFID (Radio Frequency IDentification) tags... work on the available RF (Radio Frequency) field
Implementation Method 2
To generate an internal supply from available RF field, such tags implement a full wave rectifier architecture
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
A RFID tag (1) for communicating with an external reader comprises: two antenna connections (LA, LB) for connecting the RFID tag (1) to an antenna (10), an active receiver switch circuit (5) for receiving two input sinusoidal signals from the two antenna connections (LA, LB) and generating a rectified waveform signal (8), a modulation detection circuit (12) for receiving two input sinusoidal signals from the two antenna connections (LA, LB) and generating a first demodulation signal (13) related to a 10% amplitude modulation of a RF field for communication between the reader and the RFID tag (1) and a second demodulation signal (14) related to a 100% amplitude modulation of a RF field for communication between the reader and the RFID tag (1).