RFID Receiver AM Noise Compensation via Transmitter Signal Modulation
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Solution Overview
Problem
Passive RFID systems face challenges in reducing amplitude modulation (AM) noise, which degrades receiver sensitivity due to self-blocker signals, especially in reader-to-reader interference scenarios, and conventional noise cancellation methods are costly and complex, requiring high signal-to-noise ratios and increased current drain.
Innovation Solution
An apparatus and method that modulate the received signal with a correction signal derived from the transmitter's AM noise, using a noise compensation function to reduce AM noise at the receiver, avoiding circuit reconfiguration in the transmitter path and maintaining signal integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional noise cancellation methods are used to reduce AM noise impact on receiver, then receiver sensitivity is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent extracts only the necessary noise compensation function from complex conventional cancellers. Instead of implementing full noise cancellation systems, the invention uses a simplified approach that derives correction signals from the transmitter signal itself, removing unnecessary circuitry while maintaining effectiveness in reducing AM noise impact on receiver sensitivity
Solution Approach 2:
The system uses the transmitter's own signal as the source for generating correction signals. The transmitter signal is processed to create error signals that are fed back to correct receiver sensitivity degradation, eliminating the need for external complex cancellation systems and making the system self-sufficient
2Reliability
If high signal-to-noise ratio is maintained throughout transmitter chain to reduce AM noise, then receiver sensitivity is improved, but current drain increases due to higher current requirements in D/A converters, baseband gain, low-pass filtering, and modulator stages
Solution Approach 1:
The patent implements feedback by deriving correction signals from the transmitter signal and feeding them back to the receiver. This feedback mechanism allows the system to maintain receiver sensitivity without requiring high current drain throughout the transmitter chain, as the correction is applied at the receiver end based on the actual transmitted signal characteristics
Solution Approach 2:
The invention changes the approach from maintaining high signal-to-noise ratio through increased current in transmitter stages to using signal processing parameters. By processing the transmitter signal to extract noise characteristics and applying correction through modulation, the system achieves sensitivity improvement without increasing current drain in power-intensive components
3Reliability
If conventional cancellers are used to track changing signal reflections from environment, then noise cancellation effectiveness is improved, but device complexity and difficulty of operation increase
Solution Approach 1:
The patent performs preliminary action by using the transmitter signal itself as the reference for generating correction signals. Instead of needing to track and adapt to changing environmental reflections in real-time, the system pre-establishes the correction mechanism based on the known transmitter signal characteristics, making it inherently adaptive without complex tracking circuitry
Data Source
AI summary
A method and apparatus for compensation of noise in a Radio Frequency Identification (RFID) device through modulation of a received signal is described. The method includes determining an amplitude signal proportional to an amplitude of a transmitter signal and associated noise; processing the amplitude signal to derive a correction signal; and modulating a received signal during a receive period with the correction signal to substantially remove the associated noise from the received signal. An RFID device and an RFID transceiver integrated circuit (IC) are also described.