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Modern microwave radar technologies and systems are taking important roles in healthcare, security, and human-machine interface by remote sensing of human life activities. This paper first reviews the developments in the past decade on the sensing front-end, transponder tag, and leveraging of other wireless infrastructure such as Wi-Fi. Based on the state-of-the-art engineering technologies, several emerging applications will then be studied, including continuous authentication, behavior recognition, human-aware localization, occupancy sensing, blood pressure monitoring, and sleep medicine. As radio frequency spectrum becomes a scarce resource, the allocation and spectrum sharing of life activity sensing bandwidth with other wireless infrastructures will be discussed. Several future research directions will be laid out to solve challenges for ubiquitous deployment of these sensing technologies at the human-microwave frontier.

This paper presents a pulse-stimulus sensor readout circuit for use in cardiovascular disease examinations. The sensor is based on a gold nanoparticle plate with an antibody post-modification. The proposed system utilizes gated pulses to detect the biomarker Cardiac Troponin I in an ionic solution. The characteristic of the electrostatic double-layer capacitor generated by the analyte is related to the concentration of Cardiac Troponin I in the solvent. After sensing by the transistor, a current-to-frequency converter (I-to-F) and delay-line-based time-to-digital converter (TDC) convert the information into a series of digital codes for further analysis. The design is fabricated in a 0.18-μm standard CMOS process. The chip occupies an area of 0.92 mm2 and consumes 125 μW. In the measurements, the proposed circuit achieved a 1.77 Hz/pg-mL sensitivity and 72.43 dB dynamic range.

This article presents a fully integrated 100-GHz continuous-wave Doppler radar transceiver with the double-sideband low-intermediate-frequency (IF) architecture for mechanical vibration and vital sign detection. Fabricated in a 65-nm CMOS process, the whole radar chip transceiver consumes 262 mW with a size of 0.9 mm $\times2.0$ mm. Instead of utilizing a fundamental 100-GHz voltage controlled oscillator (VCO) in the chip, a push–push frequency doubler with the 50-GHz external source is adopted to drive the transceiver. Under a dedicated design on the system architecture and circuit blocks, the chip could transmit 4-dBm saturated power ( $P_{\mathrm {sat}}$ ) over 93–105 GHz with a 40-mV 1-kHz IF carrier and achieve good I/Q performance of phase mismatch $\mu \text{m}$ displacement from 1.5 m, the human vital-sign signal from 2 m, and even a small bullfrog’s hybrid respiratory motion from 0.6 m. To the best of our knowledge, this is the first 100-GHz CMOS Doppler radar transceiver chip with the low-IF architecture for the biological vital sign detection.

The advancement of vital sign radar technology has proven to be a useful tool in assessing various physiological dynamics, including heartbeat and respiration. There remains several signal processing challenges in this field, which include overcoming the nonlinearities and harmonics that populate the power spectrum. Respiration harmonics distort and overwhelm the measurement of heartbeat due to the large signal amplitude. A supervised machine learning algorithm, the gamma filter, offers an efficient, calibration-free solution to model the time series heartbeat signal given respiration and respiration artifacts. The measured signal is provided by a 5.8-GHz quadrature Doppler radar and a modified electrocardiogram signal is used as the ground truth for training the filter. Experimental results show that the heartbeat is independent and separable from respiration and the algorithm can be implemented in real time.

The SARS-CoV-2 pandemic has had a significant impact worldwide. Currently, the most common detection methods for the virus are polymerase chain reaction (PCR) and lateral flow tests. PCR takes more than an hour to obtain the results and lateral flow tests have difficulty with detecting the virus at low concentrations. In this study, 60 clinical human saliva samples, which included 30 positive and 30 negative samples confirmed with RT-PCR, were screened for COVID-19 using disposable glucose biosensor strips and a reusable printed circuit board. The disposable strips were gold plated and functionalized to immobilize antibodies on the gold film. After functionalization, the strips were connected to the gate electrode of a metal-oxide-semiconductor field-effect transistor on the printed circuit board to amplify the test signals. A synchronous double-pulsed bias voltage was applied to the drain of the transistor and strips. The resulting change in drain waveforms was converted to digital readings. The RT-PCR-confirmed saliva samples were tested again using quantitative PCR (RT-qPCR) to determine cycling threshold (Ct) values. Ct values up to 45 refer to the number of amplification cycles needed to detect the presence of the virus. These PCR results were compared with digital readings from the sensor to better evaluate the sensor technology. The results indicate that the samples with a range of Ct values from 17.8 to 35 can be differentiated, which highlights the increased sensitivity of this sensor technology. This research exhibits the potential of this biosensor technology to be further developed into a cost-effective, point-of-care, and portable rapid detection method for SARS-CoV-2.

In this paper, four kinds of conductive threads were studied and their uses on embroidered coils for wireless charging system were examined. The results show that the embroidered coils can achieve a quality factor of at least 3 without compromising the mechanical performance of the textile. A coil was embroidered directly on a T-shirt which shows that the fabrication of embroidered receiver (RX) coil might be integrated into the clothing manufacturing process.

RF surface coils are commonly used as receivers in Magnetic Resonance Imaging (MRI) systems to acquire sensitive signals from the human body. These coils rely on cables for power and transferring information from the patient to the computer for processing. Higher image quality and faster scan times are possible by using an array of surface coils, and there is a constant need for high-density surface coil arrays. Each array element utilizes at least three cables and, increasing the number of elements in the array also increases the number of cables, making the cable bundle bulkier. This makes the placement of cables complicated for the operators and may cause patient harm when improperly positioned. Wireless technologies can eliminate cables, and this paper proposes a novel design for harvesting the ambient RF energy present during the transmit phase of the MRI system operation. After introducing the surface coil's building blocks, the importance of the decoupler as a mechanism for safety and image quality is detailed. The paper presents the analysis and design of an RF energy harvesting circuit that couples to the decoupler circuit. Its performance is tested both in simulation and the Philips Ingenia 3.0 T MRI system. The results show that the circuit successfully harvests energy, up to 1 W, during the MRI's transmit phase without any adverse effects on the decoupler or surface coil. To make energy harvesting (EH) beneficial, a new GaN -based FET switch that consumes low power is also proposed.

Radiofrequency surface coils used as receivers in magnetic resonance imaging (MRI) rely on cables for communication and power from the MRI system. Complex surface coil arrays are being designed for improving acquisition speed and signal-to-noise ratio. This, in-turn makes the cables bulky, expensive, and the currents induced on cables by time-varying magnetic fields of the MRI system may cause patient harm. Though wireless power transfer (WPT) can eliminate cables and make surface coils safer, MRI poses a challenging electromagnetic environment for WPT antennas because the antennas made using long conductors interact with the static and dynamic fields of the MRI system. This paper analyses the electromagnetic compatibility of WPT antennas and reveals that commercially available antennas are not compatible with MRI systems, presenting a safety risk for patients. Even when the risk is minimized, the antennas couple with surface coils leading to misdiagnosis. This paper presents an approach to eliminate safety risks and minimize coupling using a filter named “floating filter.” A WPT antenna without a filter has a distortion of 27%, and floating filters reduce the distortion to 2.3%. Secondly, the floating filter does not affect the power transfer efficiency, and the transfer efficiency of 60% is measured with and without filters.

Ga2O3 is a candidate for power electronics due to its large bandgap, controllable doping and availability of large inexpensive substrates. These include power conditioning systems, pulsed power for avionics and electric ships, solid-state drivers for heavy electric motors and advanced power management and control electronics. There are already cases where the performance exceeds the theoretical values for SiC. Existing Si, SiC (vertical devices), and GaN (lateral devices) enjoy advantages in terms of process maturity, especially for Si, where devices such as super-junctions surpass the unipolar "limit". Continued development of low defect substrates, optimized epi growth and improved device design and processing methods for Ga2O3 are required to push the experimental results closer to their theoretical values. The actual experimental value of VB is well below the theoretical predictions. Thermal management is a key issue in Ga2O3 power devices and initial studies have appeared on both the experimental and theoretical fronts.

An inductive load test circuit was used to measure the switching performance of fieldplated edge-terminated Schottky rectifiers with a reverse breakdown voltage of 760 V (0.1 cm diameter, 7.85 × 10-3cm2 area) and an absolute forward current of 1 A on 8 μm thick epitaxial ß-Ga2O3 drift layers. The recovery characteristics for these vertical geometry ß-Ga2O3 Schottky rectifiers switching from forward current of 1 A to reverse off-state voltage of -300 V showed a recovery time (trr) of 64 ns. There was no significant temperature dependence of trr up to 150 °C.

In this paper, we report a method of using embroidery to fabricate textile inductor coils for wireless charging of wearable sensor devices on smart garments. Electrical properties of embroidered coils are measured and compared with simulation. A process of making embroidered coils with crossover connections is proposed. An embroidered coil array structure is designed and tested in two wireless charging systems and the results show that it can charge a lithium-ion battery with currents ranging up to 100 mA.

Detection of the SARS-CoV-2 spike protein and inactivated virus was achieved using disposable and biofunctionalized functional strips, which can be connected externally to a reusable printed circuit board for signal amplification with an embedded metal-oxide-semiconductor field-effect transistor (MOSFET). A series of chemical reactions was performed to immobilize both a monoclonal antibody and a polyclonal antibody onto the Au-plated electrode used as the sensing surface. An important step in the biofunctionalization, namely, the formation of Au-plated clusters on the sensor strips, was verified by scanning electron microscopy, as well as electrical measurements, to confirm successful binding of thiol groups on this Au surface. The functionalized sensor was externally connected to the gate electrode of the MOSFET, and synchronous pulses were applied to both the sensing strip and the drain contact of the MOSFET. The resulting changes in the dynamics of drain waveforms were converted into analog voltages and digital readouts, which correlate with the concentration of proteins and virus present in the tested solution. A broad range of protein concentrations from 1 fg/ml to 10 μg/ml and virus concentrations from 100 to 2500 PFU/ml were detectable for the sensor functionalized with both antibodies. The results show the potential of this approach for the development of a portable, low-cost, and disposable cartridge sensor system for point-of-care detection of viral diseases.