A Battery-Less Wireless Respiratory Sensor Using Micro-Machined Thin-Film Piezoelectric Resonators

Abstract

In this work, we present a battery-less wireless Micro-Electro-Mechanical (MEMS)-based respiration sensor capable of measuring the respiration profile of a human subject from up to 2 m distance from the transceiver unit for a mean excitation power of 80 µW and a measured SNR of 124.8 dB at 0.5 m measurement distance. The sensor with a footprint of ~10 cm2 is designed to be inexpensive, maximize user mobility, and cater to applications where disposability is desirable to minimize the sanitation burden. The sensing system is composed of a custom UHF RFID antenna, a low-loss piezoelectric MEMS resonator with two modes within the frequency range of interest, and a base transceiver unit. The difference in temperature and moisture content of inhaled and exhaled air modulates the resonance frequency of the MEMS resonator which in turn is used to monitor respiration. To detect changes in the resonance frequency of the MEMS devices, the sensor is excited by a pulsed sinusoidal signal received through an external antenna directly coupled to the device. The signal reflected from the device through the antenna is then analyzed via Fast Fourier Transform (FFT) to extract and monitor the resonance frequency of the resonator. By tracking the resonance frequency over time, the respiration profile of a patient is tracked. A compensation method for the removal of motion-induced artifacts and drift is proposed and implemented using the difference in the resonance frequency of two resonance modes of the same resonator.

[Retracted] Using Color Difference Compensation Method to Balance and Repair the Image of Art Design

“…e common disadvantage is that the restoration effect is not good when the chromatic aberration pixel-level is reduced. Li et al [8] proposed a fuzzy color image based on multi-scale spectrum separation deviation algorithm, the white balance in the process of image feature extraction cascade classifier design spectrum characteristics of the image recognition, as a pheromone realization of white balance and compensation pixel level fusion, but the disadvantage of the method of computing cost is larger, e real-time performance is not good, and its application value in the fields of real-time video monitoring and image tracking processing is not high [9].…”

A Micromechanical Transmitter with Only One BAW Magneto-Electric Antenna

“…One of the main reasons is that the sizes of the antennas used for signal transmission are too large to be integrated in IMDs [7][8][9]. In addition, the existing IMDs require an additional power source, which could further increase the size of the entire IMDs [10][11][12]. A number of transducers used to provide power sources in IMDs have successfully reduced the size to the scale of the diameter of a piece of human hair [13][14][15][16].…”

Theoretical and Experimental Investigation of a Rotational Magnetic Couple Piezoelectric Energy Harvester

“…Therefore, piezoelectric energy harvesting has been studied by many scholars [1,2]. For example, Moradian et al proposed a battery-less wireless Micro-Electro-Mechanical (MEMS)-based respiration sensor that can be applied in the medical field [3]. It is more convenient to monitor the patient's breathing status over a long time period.…”