RFID Reader Delay Matching for Noise Cancellation
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Solution Overview
Problem
RFID reader systems face interference issues due to noise between the sending and receiving portions, leading to degradation of receiver sensitivity, particularly in monostatic and bistatic antenna configurations.
Innovation Solution
The implementation of a RFID reader circuit with RF bandpass filters providing identical or nearly identical delay in both transmitting and receiving paths, coupled with a mixer module that multiplies signals from these filters to recover backscatter sidebands and cancel noise, effectively mitigates interference by matching signal delays and phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a monostatic antenna configuration is used where the same antenna transmits and receives signals, then the device complexity is reduced, but the receiver sensitivity deteriorates due to interference from the strong transmitter signal
Solution Approach 1:
The patent segments the transmitter and receiver signal paths by introducing separate filtering paths with bandpass filters. The transmitter path includes a bandpass filter (BPF1) and the receiver path includes another bandpass filter (BPF2), allowing independent optimization of each path while using a shared antenna. This segmentation enables the system to maintain simplicity while improving receiver sensitivity through delayed signal processing.
2Measurement precision
If a bistatic antenna configuration is used with separate transmit and receive antennas, then the receiver sensitivity is improved by isolating the receiver from transmitter interference, but the device complexity increases
Solution Approach 1:
The patent merges the transmit and receive functions into a single antenna system while maintaining separate signal processing paths. By combining the antenna resources but separating the signal paths with distinct bandpass filters and delay elements, the system achieves the interference isolation benefits of a bistatic configuration without the complexity of separate antennas and their associated matching networks.
3Productivity
If bandpass filters with different delays are used in the transmit and receive paths, then the filtering performance is optimized for each path, but the noise cancellation effectiveness deteriorates due to phase mismatch
Solution Approach 1:
The patent carefully controls the delay parameter of the bandpass filters to be equal or nearly equal in both transmit and receive paths. This parameter matching ensures that the phase relationships are preserved, allowing effective noise cancellation through correlation while still providing the filtering performance benefits. The delay equality is a critical parameter that enables both filtering optimization and noise cancellation.
4Length of moving object
If the transmitter signal is strongly amplified to increase communication range, then the communication range is extended, but the receiver sensitivity deteriorates due to the stronger interfering signal
Solution Approach 1:
The patent introduces bandpass filters as intermediary elements between the transmitter amplifier and the receiver. These filters act as mediators that allow the strong transmitter signal to be amplified for extended range while simultaneously shaping the signal spectrum to facilitate later noise cancellation. The filters serve as intermediaries that enable both strong transmission and sensitive reception by preparing the signals for correlation-based processing.
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 configuration enhances the receiver's sensitivity by effectively canceling noise and isolating backscatter sidebands from the stronger transmitter signal, improving the overall performance of RFID systems.
Implementation Method 1
The mixer module receives a signal from the first RF bandpass filter and a signal from the second RF bandpass filter, the mixer module multiplies the signal from the first RF bandpass filter with the signal from the second RF bandpass filter to recover the backscatter sidebands
Implementation Method 2
the first and second RF bandpass filters provide identical or nearly identical delay of signals
Data Source
AI summary
In one embodiment, a Radio Frequency Identification (RFID) reader circuit includes a Radio Frequency (RF) source, a RF power amplifier coupled to an output of the RF source in a transmitting path, a first RF bandpass filter coupled between the output of the RF source and a mixer module, and a low noise amplifier in a receiving path being coupled to an input of a second RF bandpass filter. The mixer module receives a signal from the first RF bandpass filter and a signal from the second RF bandpass filter, the mixer module multiplies the signal from the first RF bandpass filter with the signal from the second RF bandpass filter to recover the backscatter sidebands in the signal from the second RF bandpass filter, and the first and second RF bandpass filters provide identical or nearly identical delay of signals. Other systems, methods and circuits are also described.