Wireless Sensor Reader Resonant Frequency Tuning
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Solution Overview
Problem
Wireless sensor systems face challenges in measuring weak signals with wide full-scale ranges, particularly when only a small subset of the range is used for individual measurements, and in accurately determining gauge pressure without direct access to atmospheric pressure, while also dealing with noise interference and signal attenuation.
Innovation Solution
A wireless reader device that emits a short pulse to excite the sensor, amplifies the ring signal, and uses a phase-locked loop to determine the sensor's resonant frequency, with tunable components to focus on a specific passband window corresponding to the ambient pressure, enhancing signal-to-noise ratio and reducing unwanted interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the reader uses a wide frequency range to cover all possible sensor resonant frequencies, then it can measure any pressure range, but the signal-to-noise ratio decreases and measurement precision is reduced
Solution Approach 1:
The reader dynamically adjusts its operating frequency and passband width based on ambient pressure conditions. The center frequency of the passband is tuned to match the expected sensor resonant frequency, which varies with ambient pressure. This dynamic adaptation allows the system to maintain high signal-to-noise ratio while covering a wide pressure range through multiple measurement cycles
Solution Approach 2:
The system changes the frequency parameter of the reader's receiver and excitation pulse based on ambient pressure measurements. By adjusting the center frequency and bandwidth of the receiver's passband to match the sensor's resonant frequency at the current ambient pressure, the system optimizes signal detection while rejecting out-of-band noise and interference
2Measurement precision
If the reader uses a narrow passband to improve signal-to-noise ratio, then measurement precision improves, but the ability to measure gauge pressure without direct atmospheric pressure access is limited
Solution Approach 1:
The system performs preliminary measurement of ambient pressure using an integrated barometer before conducting sensor measurements. Based on this preliminary ambient pressure information, the reader pre-tunes its passband center frequency to match the expected sensor resonant frequency. This preliminary action enables accurate gauge pressure measurement by establishing the correct frequency reference before the actual measurement cycle begins
Solution Approach 2:
The ambient pressure sensor (barometer) acts as an intermediary that provides information about atmospheric pressure conditions. This intermediary measurement allows the system to calculate the expected sensor resonant frequency and adjust the receiver's passband accordingly, enabling gauge pressure measurement without direct access to atmospheric pressure at the sensor location
3Reliability
If the reader transmits continuous excitation signals to maintain sensor resonance, then signal strength is maintained, but energy consumption increases
Solution Approach 1:
The reader transmits excitation pulses periodically rather than continuously. Each excitation pulse briefly drives the sensor into resonance, producing a ring-down signal that the reader then measures. By spacing these excitation pulses appropriately and using the sensor's natural ring-down response, the system maintains sufficient signal strength for measurement while dramatically reducing average power consumption compared to continuous excitation
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 allows for more accurate and efficient measurement of sensor signals by narrowing the passband to capture only the relevant frequency range, increasing signal strength and reducing noise, thereby improving the accuracy of pressure readings, including gauge pressure measurements, even in environments where atmospheric pressure is not directly accessible.
Implementation Method 1
the sensor transduces a physical parameter into a signal frequency... the sensor to emit a ring signal at its resonant frequency
Implementation Method 2
A reader is then configured to receive and measure the frequency of the sensor signal... A voltage-controlled oscillator in the phase-locked loop locks onto the ring signal frequency and generates a count signal at a frequency related to the ring signal frequency
Data Source
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AI summary
Summarizing a system for obtaining a measurement from a remote location comprises a wireless sensor configured to change its resonant frequency in proportion to at least one sensed parameter; and a reader configured to define a band of resonant frequency values, to optimize itself for operation based on said band, to transmit an excitation pulse at only a fixed frequency to said wireless sensor, to receive a signal from said wireless sensor in response to said excitation pulse, and to sample and hold said received signal.