Implanted Wireless Sensor Frequency Locking
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Solution Overview
Problem
Current methods for communicating with implanted wireless sensors, such as those monitoring abdominal aortic aneurysm pressure, are inefficient in terms of energy usage and prone to errors due to high power requirements and sensitivity issues, particularly in detecting small leaks or stent-graft failures, which can lead to inaccurate pressure readings.
Innovation Solution
A system that uses a low duty cycle, gated series of RF energy bursts to determine the resonant frequency of the sensor, adjusting frequencies based on phase differences to efficiently lock onto the sensor's resonant frequency, thereby reducing energy waste and improving accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a transmission signal having multiple frequencies is used to determine resonant frequency, then the resonant frequency can be identified, but energy is wasted in frequency bands outside the resonant frequency, resulting in increased power consumption, cost, size, thermal requirements, and electromagnetic interference
Solution Approach 1:
The patent applies periodic action by using a frequency sweep method where the transmission signal cycles through multiple frequencies in a systematic sequence. The system transmits at different frequencies periodically, measures the sensor response at each frequency, and identifies the resonant frequency where maximum energy transfer occurs. This periodic frequency sweeping allows accurate resonant frequency determination while concentrating energy transmission only when needed at each frequency step, rather than continuously transmitting across all frequency bands simultaneously.
2Reliability
If high power is used to transmit signals to the implanted sensor, then the signal can be detected, but the sensor signal is weak and dissipates quickly, requiring quick detection and low power operation
Solution Approach 1:
The patent implements feedback by continuously monitoring the sensor's response signal strength and using this information to adjust the transmission power and frequency. The system measures the reflected or backscattered signal from the sensor and uses this feedback to optimize the transmission parameters. When the sensor is detected and its resonant frequency is identified, the system adjusts transmission power to maintain reliable communication while minimizing energy consumption, preventing both signal loss and excessive power usage.
3Use of energy by moving object
If the resonant frequency determination method is optimized for energy efficiency, then power consumption is reduced, but the system must still handle switching transients and false locking issues
Solution Approach 1:
The patent applies preliminary action by performing calibration and characterization of the sensor system before actual measurements. The system first sweeps through frequencies to identify the resonant frequency and characterizes the sensor's response characteristics. This preliminary characterization allows the system to establish reference values and detection thresholds that prevent false locking. By preparing the system in advance with accurate frequency and response data, the patent avoids the need for high power continuous transmission during measurement, thereby reducing power consumption while maintaining measurement accuracy.
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 communication with implanted sensors, reducing the risk of false locks and energy inefficiencies, enabling real-time monitoring of pressure within the aneurysm sac and improving the detection of potential leaks or stent-graft failures.
Implementation Method 1
At least one of the energizing signals induces a current in the sensor which is maximized when the energizing frequency is the same as the resonant frequency of the sensor
Implementation Method 2
determines the resonant frequency of the sensor... The resonant frequency can be used to calculate a measured physical parameter
Data Source
Figure 1
Figure 2a~2d
Figure 3
AI summary
Aspects of the present invention determine the resonant frequency of a sensor by obtain sensor signals in response to three energizing signals, measure the phase of each sensor signal, and using a group phase delay to determine the resonant frequency. The phase difference between the first and second signal is determined as a first group phase delay. The phase difference between the second and third signal is determined as a second group phase delay. The first group phase delay and second group phase delay are compared. Based on the comparison, the system may lock on the resonant frequency of the sensor or adjust a subsequent set of three energizing signals.