Bistatic RF Switch Matrix for Incontinence Detection
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Solution Overview
Problem
Existing wireless incontinence detection systems face signal-to-interference ratio issues due to strong interfering signals from the antenna and biological tissue, leading to communication channel degradation and difficulty in detecting weak signals from RFID tags.
Innovation Solution
The system employs a bistatic RF switch matrix with multiple antennae configurations for efficient energy transmission and data reception, using a frequency hopping scheme and ceramic patch antennae to improve signal isolation and prevent conductive paths from patient fluids, coupled with remote validation and encryption for secure data transmission.
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 patent divides the single antenna system into separate transmit and receive antennas (spatial segmentation). The transmit antenna and receive antenna are physically separated and positioned at different locations, allowing independent optimization of each antenna's function while reducing mutual interference and signal loss.
Solution Approach 2:
The patent transitions from a monostatic (single-point) architecture to a bistatic (multi-point) architecture by introducing spatial separation between transmit and receive antennas. This dimensional change from co-located to distributed antenna configuration enables better signal isolation and reduced coupling effects.
2Ease of operation
If the antenna impedance deviates from the transmission line characteristic impedance, then the power reflected from the antenna is coupled into the receiver input, but the reflected signal is much stronger than the backscattered signal from the RFID tag
Solution Approach 1:
The patent introduces an isolator as an intermediary component between the transmit antenna and receive antenna. The isolator acts as a directional device that allows power to flow from the transmit antenna to the RFID tag while blocking reflected power from entering the receive antenna, thereby protecting the receiver from strong reflected signals.
Solution Approach 2:
The patent extracts the harmful reflected signal path from the receiver input by using the isolator to redirect reflected power away from the receive antenna. This separation removes the source of interference (reflected power) from the detection path, allowing the weak backscattered signal to be detected without being overwhelmed by reflections.
3Power
If forward power coupling into the receiver port is present, then the forward power can be 5 dB higher than the tag backscattered signal, but this strong signal adds to the front end of the receiver causing overload and intermodulation distortion
Solution Approach 1:
The isolator serves as a mediator that controls the direction of power flow. It allows the transmit antenna to radiate forward power at high levels while simultaneously blocking this forward power from coupling into the receive antenna, thus protecting the receiver from overload and distortion.
4Power
If power reflected from the RF forward power is present, then the reflected power can be 34 dB stronger than the backscattered signal, but this creates a very strong signal close in frequency to the weak signal of interest
Solution Approach 1:
The isolator acts as a directional mediator that permits power transmission in the forward direction (from transmit antenna to RFID tag) while blocking power flow in the reverse direction (from RFID tag reflections back to receive antenna). This directional control eliminates the strong reflected signal from the receiver input, dramatically improving the signal-to-interference ratio for detecting weak backscattered signals.
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 signal detection and reduces interference, improving the accuracy and reliability of incontinence detection while ensuring secure data communication and efficient pad validation.
Implementation Method 1
a first antenna of the plurality of antennas is established as a transmit antenna that is used to wirelessly energize the passive RFID tag
Implementation Method 2
a second antenna of the plurality of antennas is established as a receive antenna that is used to read backscattered data that is emitted from the passive RFID tag
Data Source
AI summary
An incontinence detection pad has an RFID tag in which an authentication code, such as an electronic product code (EPC), is stored. A reader in wireless communication with the RFID tag of the incontinence detection pad verifies that the incontinence detection pad is an authorized detection pad. Thus, unauthorized incontinence detection pads that do not have the proper authentication code are not able to be used in an incontinence detection system.