Simulation of coil separation and angle effects on the mutual inductance for 13.56 MHz WRAP sensors

IET Wireless Sensor Systems

2021

Self Cite

Monitoring physiological signals during regular life might provide many benefits including early detection of abnormalities and tracking the severities of diseases. A wireless connection between the passive sensor and the scanner eliminates the obtrusive wires, resolves battery-related issues, and makes it easy-to-use. We have previously proposed a wireless resistive analogue passive sensor technique that operates with the help of inductive coupling. The variation of resistive physiological transducer (secondary side) leads to amplitude modulation on the scanner coil (primary side). The design of printed spiral coil (PSC) on printed circuit board, significantly affects the performance of the overall system in terms of sensitivity, the output voltage change as a reflection of the transducer change. To optimize the PSC's profile and maximize the sensitivity, we employ three methods: iterative, analytical, and genetic algorithm (GA). The GA optimized PSCs, as the best result, have been fabricated and the measurement showed a sensitivity of 0.72 mƱ which has 5% (8.8%) deviation from the simulation (theoretical) results. This method can be utilized to design a PSC pair in near-field applications to transfer amplitude modulation with various sizes and fabrication constraints. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Section: Measuring the Coupling Factor (K)supporting

confidence: 80%

Section: Measuring the Coupling Factor (K)mentioning

confidence: 99%

Design and optimization of printed spiral coils for wireless passive sensors

Noroozi

IET Wireless Sensor Systems

2021

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“…7 with respect to resistance can be addressed by utilising an inverse model of the non‐linearity curve. These are our current active research areas [19, 21].…”

Section: Discussionmentioning

confidence: 99%

“…We have previously reported coil design and optimisation for planar sprial coils through iterative algorithm [18]. We are also working on modelling effects of coil separation and orientation on mutual inductance [19, 20]. In case of physiological signals that depend on exact value, such as body temperature, differential measurement approach with a reference coil [21] or transformation from magnitude domain to temporal domain (e.g.…”

Section: Working Principlementioning

confidence: 99%

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

Consul-Pacareu

2018

IET wirel. sens. syst.

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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.

“…Optimal coupling can be achieved by making the diameter of the primary coil greater than the diameter of the sensor coil. The inductive link coupling coefficient is dependent on distance and alignment, such as lateral shift or the angular orientation of the secondary coil with respect to the primary, which was explored in our past study [26]. Our research group conducted an intensive study on an iterative method to find the optimal coil design which will therefore be left undiscussed in this context.…”

Section: Planar Wireless Coil Designmentioning

confidence: 99%

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

Abu-Saude

2023

Sensors

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The wireless capture of analog differential signals from fully passive (battery-less) sensors is technically challenging but it can allow for the seamless capture of differential biosignals such as an electrocardiogram (ECG). This paper presents a novel design for the wireless capture of analog differential signals using a novel conjugate coil pair for a wireless resistive analog passive (WRAP) ECG sensor. Furthermore, we integrate this sensor with a new type of dry electrode, namely conductive polymer polypyrrole (PPy)-coated patterned vertical carbon nanotube (pvCNT) electrodes. The proposed circuit uses dual-gate depletion-mode MOSFETs to convert the differential biopotential signals to correlated drain-source resistance changes and the conjugate coil wirelessly transmits the differences of the two input signals. The circuit rejects (17.24 dB) common mode signals and passing only differential signals. We have integrated this novel design with our previously reported PPy-coated pvCNT dry ECG electrodes, fabricated on a stainless steel substrate with a diameter of 10 mm, which provided a zero-power (battery-less) ECG capture system for long duration monitoring. The scanner transmits an RF carrier signal at 8.37 MHz. The proposed ECG WRAP sensor uses only two complementary biopotential amplifier circuits, each of which has a single-depletion MOSFET. The amplitude-modulated RF signal is envelope-detected, filtered, amplified, and transmitted to a computer for signal processing. ECG signals are collected using this WRAP sensor and compared with a commercial counterpart. Due to the battery-less nature of the ECG WRAP sensor, it has the potential to be a body-worn electronic circuit patch with dry pvCNT electrodes that stably operate for a long period of time.