RFID Reader Signal Filtering for Sideband Noise Reduction
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Solution Overview
Problem
RFID reader systems face interference from sideband noise when transitioning between unmodulated and modulated carrier signals, which can disrupt the low-level backscatter signals from passive RFID tags.
Innovation Solution
The RFID reader determines whether the digital input signal is unmodulated or modulated and accordingly filters or bypasses the analog signal to prevent interference, using transmitter circuitry with switches and filters to produce either filtered or unfiltered analog signals for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If the RFID reader transmits modulated carrier signals to communicate information with RFID tags, then information transmission capability is improved, but sideband noise leaks into the receiver circuitry and interferes with low-level backscatter signals
Solution Approach 1:
The patent applies dynamics by making the filter configuration adjustable based on the signal type being transmitted. The RFID reader dynamically switches between different filter states (first filter configuration for unmodulated signals, second filter configuration for modulated signals) to optimize performance for each transmission mode, thereby reducing sideband noise interference while maintaining information transmission capability
Solution Approach 2:
The patent changes the filter parameters (cutoff frequencies, bandwidth) based on the transmission mode. When transmitting unmodulated carrier signals, the filter is configured with first parameters that pass the continuous wave while attenuating sideband noise. When transmitting modulated signals, the filter parameters are adjusted to pass the modulated spectrum while still providing noise reduction
2Reliability
If the RFID reader uses filtering to reduce sideband noise, then signal clarity is improved, but transmission of unmodulated carrier signals may be degraded
Solution Approach 1:
The system dynamically adjusts the filter configuration based on the type of signal being transmitted. For unmodulated carrier signals, the filter is configured in a first state optimized for passing continuous waves. For modulated signals, the filter switches to a second state optimized for reducing sideband noise while passing modulated spectra. This dynamic adaptation ensures both transmission modes operate optimally
Data Source
AI summary
A Radio Frequency Identification (RFID) reader is provided that receives a digital input signal, converts the digital input signal to an analog input signal, and determines whether the digital input signal is an unmodulated signal or is modulated with information. When the digital input signal is modulated with information, the RFID reader filters the analog input signal to produce a filtered analog input signal and transmits the filtered signal. When the digital input signal is an unmodulated signal, the RFID reader bypasses the filtering of the analog input signal to produce an unfiltered analog input signal and transmits the unfiltered analog input signal.