Passive Wireless Sensor Tuning for Reliable RF Environmental Sensing
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Solution Overview
Problem
Current wireless communication systems, particularly RFID systems, face challenges in accurately sensing and processing environmental conditions due to limitations in power supply and signal strength, which affect the reliability and precision of data collected from passive wireless sensors.
Innovation Solution
The implementation of sensor computing devices that communicate with passive wireless sensors, using a power harvesting circuit and a tuning circuit to adjust the resonant frequency based on sensed conditions, allowing for accurate data processing and transmission of environmental data through back-scattering techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If passive wireless sensors are used to sense environmental conditions, then device complexity is reduced and ease of operation is improved, but power supply reliability and signal strength deteriorate
Solution Approach 1:
A computing device is introduced as an intermediary between the passive wireless sensor and the user/system. The computing device receives power from a power source, processes environmental data from the passive sensor, and manages communication. This intermediary handles the power supply complexity, allowing the passive sensor to remain simple while maintaining system reliability through the computing device's power management capabilities.
2Ease of operation
If passive wireless sensors are used to sense environmental conditions, then device complexity is reduced and ease of operation is improved, but signal strength deteriorates
Solution Approach 1:
The computing device acts as a signal amplifier and processor intermediary. The passive wireless sensor transmits weak environmental data signals, which the computing device receives, processes, and prepares for transmission to remote systems. This intermediary approach allows the passive sensor to maintain simplicity while the computing device handles signal strength requirements for reliable communication.
Solution Approach 2:
The system combines the passive wireless sensor with the computing device into an integrated environmental monitoring system. The sensor and computing device work together as a unified system where the sensor's simplicity is preserved while the computing device provides the necessary signal processing and communication capabilities to overcome individual signal strength limitations.
3Measurement precision
If computing device processes environmental data from passive wireless sensors, then measurement precision is improved, but use of energy increases
Solution Approach 1:
The system segments functions between the passive wireless sensor and the computing device. The passive sensor performs only the simple task of sensing environmental conditions without power consumption for processing. The computing device performs data processing and analysis to achieve measurement precision. This segmentation allows precise measurements while the passive sensor contributes zero energy consumption, and the computing device's energy use is justified by the precision it achieves.
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 solution enables reliable and precise sensing and processing of environmental conditions, such as moisture, temperature, and humidity, by ensuring optimal signal strength and power levels, thereby improving the accuracy and reliability of data collected from passive wireless sensors.
Implementation Method 1
a power harvesting circuit coupled to the antenna and configured to harvest power from the RF signal
Implementation Method 2
a tuning circuit coupled to the antenna and configured to adjust a resonant frequency of the antenna in response to the sensed environmental condition
Implementation Method 3
allowing for accurate data processing and transmission of environmental data through back-scattering techniques
Data Source
AI summary
A communication system includes a passive wireless sensor and a sensor computing device. The passive wireless sensor is operable to receive a radio frequency (RF) signal including a carrier frequency signal and a modulated sense request signal, generate a power supply voltage, determine received signal strength (RSSI) of the RF signal, and determine whether the RSSI is at a desired level. When the RSSI is at a desired level, the passive wireless sensor generates a response RF signal including the carrier frequency and a coded sense response signal representative of a sensed environmental condition. The sensed environmental condition affects impedance of a front-end of the passive wireless sensor to produce an affected impedance. The passive wireless sensor generates the coded sense response signal based on tuning the affected impedance to resonate with the carrier frequency signal. The computing device operable to: transmit the RF signal, receive the response RF signal, and generate an environmental condition value based on the coded sense response signal and environmental conversion information.