Efficient wireless power transmission to a designated location can reduce the size of implantable device and save source energy, but the receiver coil and rectifier circuit still occupy a large area. This paper proposes a novel magnetic resonant coupling (MRC)-based double figure-of-eight coil sensor system to induce and monitor heat. Implantable devices could obtain energy from the surrounding electric field or heating effect. The fundamental of generating the heating effect by the proposed coil-based sensor system is derived, and conceptual system architecture is built. Then the radiating coil is analyzed in terms of Litz-wire coil optimization, lumped parameter extraction, impedance-matching network, equivalent circuit model, and coupling coefficient. Considering the current ratio, operating frequency, and designated location, the triple-mode operation mechanism is analyzed for the first time to adjust superposed electromagnetic fields at the designated location. At the odd-mode resonance, the electric field intensity in the middle between two figure-of-eight coils is significantly improved. Finally, the physical prototype of proposed coil-based sensor system is built up and experiments are conducted to test the currents in both figure-of-eight coils as well as the induced voltage and temperature change in the in-vitro sample by using the electrode sensor and thermocouple sensor. Measurements validate the feasibility of the proposed coil-sensor system. It also provides essential guidance on designing sensors for deep-tissue stimulation and hyperthermia treatment.

A complex permittivity characterization method for liquid samples has been proposed. The measurement is carried out based on a self-designed microwave sensor with a split ring resonator (SRR), the unload resonant frequency of which is 5.05 GHz. The liquid samples in capillary are placed in the resonant zone of the fabricated senor for high sensitivity measurement. The frequency shift of 58.7 MHz is achieved when the capillary is filled with ethanol, corresponding a sensitivity of 97.46 MHz/μL. The complex permittivity of methanol, ethanol, isopropanol (IPA) and deionized water at the resonant frequency are measured and calibrated by the first order Debye model. Then, the complex permittivity of different concentrations of aqueous solutions of these materials are measured by using the calibrated sensor system. The results show that the proposed sensor has high sensitivity and accuracy in measuring the complex permittivity of liquid samples with volumes as small as 0.13 μL. It provides a useful reference for the complex permittivity characterization of small amount of liquid chemical samples. In addition, the characterization of an important biological sample (inositol) is carried out by using the proposed sensor.

A novel configuration for a Ka-band V-shaped microstrip meander-line slow-wave structure (SWS) is reported. The SWS is designed to work at a voltage less than 4 kV and provide a wide bandwidth. Coplanar waveguide (CPW) input-output feed lines and a shielding structure are incorporated to enable fast on-wafer cold test measurements on a CPW probe station without requiring dicing or a metal enclosure. Simulated dispersion characteristics and coupling impedance for the optimized design are presented. The simulated S₁₁ of the entire structure is better than -15 dB over 25-36 GHz. The proposed configuration is fabricated using 4″ Si wafers and standard microfabrication processes. The measured S₁₁ of the entire structure is better than -10 dB over 20-40 GHz. The observed high insertion loss has been explained in detail, and alternative approaches that can reduce the loss have been proposed. The PIC simulation results show that for a 3.6-kV, 50-mA sheet beam, the output power can potentially reach 14.5 W at 34 GHz with a gain of 21.6 dB. A 3-dB bandwidth of about 25% centered at 32 GHz is also indicated.

A symmetric configuration of two V-shaped microstrip meander-line slow wave structures (MLSWSs) is studied for application in Ka-band traveling-wave tubes (TWTs). Simulated dispersion characteristics and coupling impedance are presented for an optimized design. Particle-in-cell (PIC) simulation results show that for a 3.6-kV, 50-mA sheet-beam, the output power can potentially reach 28 W at 32 GHz with a gain of 28- and a 3-dB bandwidth of about 25% centered at 32 GHz. The proposed configuration is realized by first microfabricating a number of V-shaped MLSWSs on a 4'' quartz wafer and then laser-dicing individual SWSs. A metal enclosure with waveguide input-output couplers is fabricated to house the SWSs and facilitate measurements. With two of the SWSs placed symmetrically inside the metal enclosure, the measured S11 for a 150-period symmetric MLSWS is better than -15 dB over 24-40 GHz. The reasons for the measured S21 being higher than expected are identified and verified by measurements on another set of SWSs which is fabricated using printed-circuit technique. An assembly that can be used for hot-tests is also presented.

Malaria parasite- Plasmodium falciparum infection is a severe healthcare problem in tropical and subtropical regions. Early detection of such disease is vital in reducing mortality and controlling the spread in the affected areas. In this article, detecting the ring-stage malaria parasite is carried out by using the proposed photoacoustic (PA)-surface acoustic wave (SAW) sensing and detection system. By optical radiation, the PA signal is generated from the red blood cell (RBC), and then, the SAW sensor could transfer the acoustic wave into the electrical signal for the analysis. The SAW sensor is manufactured via the standard two-step lithography techniques. The proposed system consists of a tunable pulse laser device with the adjusting optical components, a PA-SAW sensor, a function generator, two analog front-end (AFE) circuits, a digital oscilloscope, a workstation for data postprocessing, and several auxiliary coaxial cables for data communications. With the acquired PA signal and its fast Fourier transform (FFT) spectrum from the various specimens, the cultured ring-stage malaria parasite in the infected whole blood could be detected at a low concentration level of 0.5% with the PA-SAW sensor. The proposed system demonstrates its excellent potential in the early diagnosis of the malaria parasite.