Bistatic RFID Antenna Matrix for Signal Isolation
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Solution Overview
Problem
Existing incontinence detection systems face signal-to-interference ratio issues due to strong interfering signals near the RFID tag, leading to communication challenges and performance degradation, especially when the antenna impedance deviates from the transmission line characteristic impedance and biological tissue interaction affects the RFID system.
Innovation Solution
The system employs a bistatic RF switch matrix with a full cycle scanning mode to optimize antenna combinations for valid reads, using a frequency hopping scheme and ½ wave ceramic patch antennas to improve signal isolation and reduce interference, and includes a remote validation process for secure and efficient data management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a monostatic architecture using a hybrid directional coupler is used to provide receiver isolation from the transmitter, then simultaneous transmission and reception on the same antenna is enabled, but the coupling between transmitter and receiver ports is about -10 dB, causing 90% of the received signal to be lost
Solution Approach 1:
The system divides the antenna array into separate transmit and receive antenna elements, physically segmenting the monostatic architecture into a bistatic configuration. This segmentation allows independent optimization of transmit and receive paths, eliminating the coupling losses inherent in monostatic hybrid coupler architectures.
Solution Approach 2:
The patent introduces a bistatic RF switch matrix as an intermediary component that manages the connection between multiple antennas and the RFID reader. This switch matrix enables dynamic configuration of antenna pairs, selecting optimal transmit-receive combinations to maximize signal quality while minimizing interference.
2Power
If the antenna impedance deviates from the transmission line characteristic impedance, then power is reflected from the antenna, but the reflected power is coupled into the receiver input and is much stronger than the backscattered signal from the RFID tag
Solution Approach 1:
The system extracts the problematic reflected power from the receiver path by using separate transmit and receive antennas. The spatial separation ensures that reflected power from the transmit antenna does not couple into the receive antenna, effectively removing the source of receiver overload while maintaining power transfer efficiency.
Solution Approach 2:
The patent converts the potential harm of impedance mismatch and reflected power into a benefit by using the reflected power as an indicator for adaptive antenna selection. The system monitors signal quality metrics and uses this information to dynamically select antenna pairs that minimize interference and maximize the backscattered signal from the RFID tag.
3Object-affected harmful factors
If a hybrid directional coupler is used to provide receiver isolation, then transmitter-receiver coupling is reduced, but the S/I ratio can be on the order of 50 dB, making it difficult to detect the weak backscattered signal
Solution Approach 1:
The patent transitions from a single-antenna monostatic architecture to a multi-antenna bistatic architecture, adding spatial dimensions to the system. By utilizing multiple transmit and receive antennas with different spatial positions and orientations, the system creates additional degrees of freedom for signal reception, enabling better separation of the weak backscattered signal from interference through spatial filtering and diversity combining.
4Adaptability or versatility
If RFID systems are located in close proximity to a patient's body, then incontinence detection is enabled, but communication channel degradation occurs due to the interaction of biological tissue and body fluids with the RFID tag
Solution Approach 1:
The system implements dynamic antenna selection and configuration based on real-time signal quality measurements. The bistatic RF switch matrix continuously monitors communication channel conditions and adapts the transmit-receive antenna pairs accordingly, allowing the system to maintain reliable communication despite the challenging electromagnetic environment created by proximity to the patient's body and interactions with biological tissues and fluids.
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 enhances the detection system's ability to accurately read RFID tags with improved signal isolation and reduces false positives, enabling reliable incontinence detection and secure data handling.
Implementation Method 1
a bistatic radio frequency (RF) switch matrix which is operable to establish a first antenna of the plurality of antennae as a transmit antenna that is used to wirelessly energize the passive RFID tag
Implementation Method 2
to establish a second antennae of the plurality of antennae as a receive antenna that is used to read backscattered data emitted from the passive RFID tag
Data Source
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AI summary
An incontinence detection system includes an incontinence detection pad (60) for placement beneath a person to be monitored. The incontinence detection pad has a passive radio frequency identification (RFID) tag (64). A reader (12) is provided and a plurality of antennae (13-16) is coupled to the reader. The reader includes a bistatic radio frequency (RF) switch matrix which is operable to establish a first antenna of the plurality of antennae as a transmit antenna that is used to wirelessly energize the passive RFID tag and to establish a second antennae of the plurality of antennae as a receive antenna that is used to read backscattered data that may be emitted from the passive RFID tag. The first and second antennae are situated in respective housings that are spaced apart from each other. An arrangement of first and second electrodes on an electrical sheet of an incontinence pad is also provided.