RFID Interrogator Distortion Cancellation via Feedback Nulling
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Solution Overview
Problem
RFID interrogators face distortion issues due to leaked transmitter energy, which can lead to misidentification of RFID tags, as the same antenna is used for both transmission and reception, and current combiners are not perfect, allowing RF energy to interfere with the received backscatter signals.
Innovation Solution
A circuit is implemented to sample and modify the transmitted signal, adding it back to the received signal to cancel out distortion, using either static or dynamic feedback mechanisms to ensure effective nulling of unwanted energy, with options including separate antennas and directional couplers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single antenna is used for both transmission and reception, then device complexity is reduced, but transmitter energy leaks into the receiver causing signal distortion
Solution Approach 1:
The patent segments the signal path by using a circulator to divide the antenna interface into distinct transmit and receive paths. The circulator directs transmitted signals from the amplifier to the antenna while routing received signals from the antenna to the receiver, preventing transmitter energy leakage into the receiver path while maintaining a single antenna configuration.
Solution Approach 2:
The circulator acts as an intermediary device between the antenna and the transmit/receive components. It mediates the signal flow by selectively directing signals based on their direction of travel, allowing the single antenna to serve both functions without causing harmful interference between transmission and reception paths.
2Measurement precision
If a combiner is used to route signals, then signal directionality is improved, but imperfect combiner performance allows RF energy to leak and distort received signals
Solution Approach 1:
The circulator serves as a superior intermediary device compared to a combiner, providing ideal signal directionality. It perfectly routes transmitted signals to the antenna and received signals to the receiver without the leakage problems inherent in combiners, thereby eliminating RF energy leakage while maintaining accurate signal routing.
Solution Approach 2:
The patent incorporates a feedback path that samples the transmitted signal, processes it through phase shifting and amplification, and subtracts it from the received signal. This feedback mechanism actively cancels out any remaining transmitter leakage and distortion, improving signal accuracy by compensating for imperfections in the signal routing path.
3Use of energy by moving object
If the transmitter continuously operates to power RFID tags, then tag power supply is ensured, but receiver distortion increases due to constant transmitter energy leakage
Solution Approach 1:
The circulator segments the transmit and receive signal paths, allowing the transmitter to operate continuously for powering RFID tags while preventing its energy from leaking into the receiver path. This physical separation enables continuous tag power supply without the harmful side effect of receiver distortion.
Solution Approach 2:
The feedback cancellation circuit continuously processes the transmitted signal and subtracts it from the received signal path. This active feedback mechanism dynamically compensates for transmitter energy leakage, enabling continuous transmitter operation for tag power supply while maintaining clean received signals free from distortion.
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 effectively removes distortion from received signals, improving the accuracy of RFID tag identification by canceling out unwanted transmitter energy, enhancing the reliability of RFID systems.
Implementation Method 1
modifies the RF energy, and introduces the modified energy back into the interrogators receiver that then nulls or cancels the unwanted distortion
Data Source
AI summary
According to several embodiments of the invention, a radio frequency identification (RFID) interrogator utilizing a circuit to remove unwanted distortion from a received signal is described. The interrogator transmits a transmitted signal continuously, while receiving a received signal from a radio frequency identification (RFID) tags. The circuit samples the transmitted signal, and removes the unwanted distortion created by the transmitted signal from the received signal.