RFID Reader AM Noise Cancellation via Signal Inversion
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Solution Overview
Problem
The existing RFID systems face challenges in improving the signal-to-noise ratio (SNR) of backscatter signals due to amplitude modulation (AM) noise, which limits the range and effectiveness of RFID readers, as this noise is not effectively mitigated by current echo or carrier cancellation schemes and is exacerbated by antenna mismatches and environmental factors.
Innovation Solution
The method involves generating a continuous wave (CW) carrier signal, detecting and inverting the AM noise component, and summing it with the CW carrier signal to create an AM noise-cancelled carrier signal, which is then transmitted, thereby reducing AM noise reflected back into the receiver and enhancing the SNR of the backscatter signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a directional device is used to separate incoming backscatter from outgoing CW energy, then some separation is achieved, but AM noise from the outgoing energy still obscures the backscatter signals
Solution Approach 1:
The patent captures the AM noise that would otherwise be harmful and uses it constructively by inverting and subtracting it from the received signal. The noise energy is converted from a detrimental factor into a useful reference for cancellation, improving the detectability of backscatter signals.
Solution Approach 2:
The system performs preliminary action by capturing and inverting the AM noise component before it can obscure the backscatter signals. By pre-processing the outgoing CW energy to extract and invert the noise component, the system prepares the cancellation signal in advance, enabling effective noise removal from the received signals.
2Reliability
If current echo or carrier cancellation schemes are used, then some noise reduction is achieved, but wideband AM noise cannot be effectively mitigated
Solution Approach 1:
The patent changes the approach from narrowband carrier frequency cancellation to wideband amplitude envelope cancellation. By working in the amplitude domain rather than the frequency domain, and by capturing the entire AM noise spectrum before transmission, the system achieves effective cancellation across wideband frequencies rather than at a single carrier frequency.
3Loss of information
If the outgoing energy has sideband energy, then the carrier can be modulated for information transmission, but the carrier sideband energy obscures the returning backscatter sideband energy
Solution Approach 1:
The patent extracts the AM noise component containing the sideband energy from the outgoing CW carrier signal. By separating and inverting only the noise portion while preserving the clean carrier, the system removes the harmful sideband energy that would otherwise obscure returning backscatter signals, allowing both transmission and reception to coexist effectively.
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 effectively cancels wideband AM noise in the carrier signal, improving the SNR of the backscatter signal and extending the operational range of the RFID reader device.
Implementation Method 1
The AM noise component is inverted to an inverted noise signal, and the inverted noise signal is summed with the CW carrier signal to provide an AM noise cancelled carrier signal
Data Source
AI summary
A method and device enables improving a signal to noise ratio (SNR) of a backscatter signal received from a radio frequency identification (RFID) tag. The method includes generating a continuous wave (CW) carrier signal at the reader device (step 505). An amplitude modulation (AM) noise component of the CW carrier signal is then detected (step 510). The AM noise component is inverted to an inverted noise signal (step 515), and the inverted noise signal is summed with the CW carrier signal to provide an AM noise cancelled carrier signal (step 520). The AM noise cancelled carrier signal is then transmitted from an antenna of the reader device (step 525), and the backscatter signal is received at the reader device in response to transmission of the AM noise cancelled carrier signal (step 530).