Wireless Sensor Reader Resonant Frequency Detection
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Solution Overview
Problem
Current passive sensor readers face issues such as large size, high power consumption, inaccuracy, and interference due to wide bandwidth requirements, which limit their use and longevity, especially in battery-powered devices.
Innovation Solution
A reader device that transmits a short pulse of energy at a fixed frequency to excite the sensor, allowing it to ring at its resonant frequency, and uses a phase-locked loop to lock onto and measure the sensor's frequency, reducing the need for wide bandwidth and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If wide bandwidth transmission is used to excite the sensor, then the sensor can be excited across different resonant frequencies, but the device size and power consumption increase
Solution Approach 1:
The reader transmits periodic frequency sweeps rather than continuous wide bandwidth signals. The frequency sweep excites the sensor resonantly at different frequencies over time, allowing the system to determine sensor resonant frequency through phase detection of the ring-down response, thereby reducing instantaneous power requirements while maintaining frequency adaptability
Solution Approach 2:
The system changes the frequency parameter dynamically by sweeping through a range of frequencies and detecting the resonant frequency of the sensor. This allows the reader to adapt to different sensor resonant frequencies without requiring continuous wide bandwidth transmission, reducing power consumption while maintaining versatility
2Measurement precision
If frequency sweep transmission is used to excite the sensor, then the sensor resonant frequency can be accurately determined, but the measurement time increases
Solution Approach 1:
The reader transmits a frequency sweep that preemptively excites the sensor across the frequency range before measurement. The sensor stores energy during the sweep and releases it as a ring-down response, allowing accurate frequency determination through phase detection without requiring prolonged measurement time
Solution Approach 2:
The system uses phase detection of the sensor's ring-down response as feedback to identify the resonant frequency. The phase detector compares the transmitted frequency with the sensor response, providing real-time feedback that enables accurate frequency measurement while minimizing measurement time
3Reliability
If high power transmission is used to excite the sensor, then the sensor response is stronger, but the device generates more electromagnetic interference
Solution Approach 1:
The reader uses periodic frequency sweeps with controlled duration and amplitude, transmitting energy in pulses rather than continuous high power. This periodic excitation provides sufficient signal strength for reliable measurement while reducing average power consumption and electromagnetic interference
Solution Approach 2:
The system converts the sensor's natural resonant behavior, which could be seen as a limiting factor, into a beneficial feature. By detecting the ring-down response and using phase detection, the system accurately determines frequency while using lower transmission power, thereby reducing electromagnetic interference while maintaining signal reliability
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
The solution enables a compact, low-power, and accurate measurement system that complies with electromagnetic regulations, suitable for battery operation and frequent use, with improved resolution and reduced interference.
Implementation Method 1
transmits a short pulse of energy at a fixed frequency to cause the wireless sensor to ring at or near its resonant frequency
Implementation Method 2
uses a phase-locked loop to lock onto and measure the sensor's frequency
Data Source
Figure 1
Figure 2
Figure 3~4A
AI summary
There is provided a wireless sensor reader comprising: a transmit circuit configured to generate at least one excitation pulse to cause a wireless sensor to emit at least one response signal corresponding to a sensed parameter value; at least one antenna configured to transmit said at least one excitation pulse and receive said at least one response signal; a receive circuit for amplifying said at least one received response signal; a digital sampling circuit for converting said at least one amplified received response signal to digital representation; a spectrum analysis circuitry for converting said digital representation of said at least one response signal to a frequency domain representation; and a frequency domain circuitry for processing of said frequency domain representation to determine said wireless sensor sensed parameter value.