Direct RF Sampling Clocking for Weak RFID Signal Detection
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Solution Overview
Problem
In dense reader environments, RFID readers face challenges in filtering out unwanted adjacent reader transmissions, leading to significant noise interference that masks the weak backscattered signals from transponders, making it difficult to accurately detect Radio Frequency (RF) signals.
Innovation Solution
The implementation of a system and method that uses a clock generator and Analog-to-Digital Converter (ADC) to directly sample RF signals, where the clock signal is generated based on the transmission signal, reducing phase noise by mixing the RF signal with the sample clock, thereby improving noise figure and reducing thermal noise effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional filtering methods are used to separate transponder signals from reader transmissions, then adjacent reader transmissions can be partially filtered, but phase noise and thermal noise from the transmitter still mask the weak backscattered signals
Solution Approach 1:
The patent extracts only the necessary frequency components of the transmitter signal by using a bandpass filter to select specific harmonics, then uses an analog-to-digital converter to capture only the relevant signal portions, effectively separating the useful signal from the noisy background
Solution Approach 2:
The patent introduces an intermediary processing stage between the transmitter and the final detection, using a clock generator synchronized to the transmitter signal to create reference frequencies that help isolate the weak backscattered signals from the strong transmitter leakage and thermal noise
2Measurement precision
If the ADC sampling rate is increased to capture weak backscattered signals, then signal detection sensitivity improves, but the noise figure and thermal noise effects worsen
Solution Approach 1:
The patent performs preliminary filtering and signal conditioning before the ADC conversion stage, using bandpass filters to pre-select the frequency band of interest and remove out-of-band noise, thereby reducing the noise burden on the ADC and improving the effective signal-to-noise ratio
Solution Approach 2:
The patent replaces traditional analog mixing and frequency conversion mechanisms with direct ADC sampling of the RF signal, using digital signal processing to perform frequency translation and filtering, which reduces the number of analog components that contribute to thermal noise
3Productivity
If multiple readers operate in the same environment, then system productivity and coverage area increase, but interference from adjacent readers masks the backscattered signals
Solution Approach 1:
The patent maintains continuous synchronization with the transmitter signal by using a clock generator that is phase-locked to the reader's own transmission, ensuring that the sampling process continuously tracks the transmitter frequency and phase, which allows for consistent rejection of adjacent reader interference
Solution Approach 2:
The patent changes the sampling parameters dynamically by adjusting the ADC sampling rate and clock generator frequency to match the specific transmitter frequency being monitored, allowing the system to adapt to different operating conditions and frequency allocations in dense reader environments
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 reduces transmitter phase noise, improves signal quality, and supports multiple protocols by digitally filtering and down-converting RF signals, enhancing the detection of weak backscattered signals in dense reader environments.
Implementation Method 1
Mixing of the RF signal and the sample clock, through the sampling process in the ADC, reduces phase noise associated with the transmission signal in the receive path
Data Source
AI summary
The present disclosure is directed to a system and method for directly sampling RF signals. In some implementations, an RF reader includes a clock generator and an Analog-to-Digital Converter (ADC). The clock generator is configured to generate a sample clock signal based, at least in part, on an input signal associated with transmitting RF signals. The ADC is configured to directly sample RF signals in a receive path of the reader using the sample clock signal to generate a digital signal. Mixing of the RF signal and the sample clock, through the sampling process in the ADC, reduces phase noise associated with the transmission signal in the receive path.