Design and analysis of a novel wireless resistive analog passive sensor technique

Abstract

Unobtrusive monitoring of physiological signals in natural settings is important for precision diagnostics. Fully‐passive wireless body‐worn sensors are viable and promising for unobtrusive monitoring. In this study, the authors present a new class of fully‐passive sensor, namely wireless resistive analog passive (WRAP) sensor. It uses resistive transducers at the sensors for converting physical stimulus to load modulation of carrier wireless signal at 13.56 MHz at low power (–20 to 0 dBm). The sensor is simply composed of a loop antenna, a tuning capacitor, and a resistive transducer suitable for the type of physiological signals to be measured. The authors report the characterisation of WRAP sensors for various resistive loads of 1.2 ω to 82 kω at various co‐axial distances (5–40 mm) between the TX and RX antennas. They have prototyped and characterised multiple WRAP sensors with several practical measurements of physiological signals such as heart rate, temperature, and pulse oximetry. They also demonstrate bio‐potential measurement (down to 400 μVpp) using metal–oxide–semiconductor field‐effect transistor as the transducer. These results show the feasibility of developing a new type of body‐worn fully‐passive WRAP sensors for unobtrusive physiological signal monitoring at real‐life settings for precision diagnostics of many disorders and tracking person‐centric therapy efficacy.

Inductive Coupling of Bipolar Signals with a Conjugate Coil Pair for an Analog Passive ECG Sensor Using a PPy-Coated pvCNT Dry Electrodes

“…Three electrodes are connected to the human body (e.g., to capture an ECG signal) as shown in Figure 3c. We have previously reported biopotential capture with single-gate enhancement and depletion-mode MOSFETs [17,20]. However, single-gate MOSFET amplifications were insufficient in collecting ECG signals with inductive coupling.…”

“…The novel WRAP sensor is based on an LC resonance that is inductively coupled between two printed spiral coils (PSCs). Various physiological signals have been captured such as respiration rate, heart rate, and core body temperature [16][17][18][19][20].…”

Long-Range Detection of a Wirelessly Powered Resistive Transducer

“…Alternatively, passive resonators have been utilized to estimate resistance changes. By connecting the sensing resistor in parallel [ 29 ]–[ 32 ] or in series [ 33 ], [ 34 ] to an resonator, resistance changes can affect the line shape of the resonator’s frequency response curve that can be inductively measured by an external network analyzer. However, line shape analysis is a complex nonlinear procedure, leading to lower temperature resolution (1.2 °C in Table I ).…”

Signal Recovery Performance Analysis in Wireless Sensing with Rectangular-Type Analog Joint Source-Channel Coding

“…To reduce the power consumption of wireless digital sensors, low-power ADC designs are proposed [18]- [21]. In contrast to digital sensors, analog sensor designs have been proposed [22], [23] without ADC and digital components.…”