In this paper, a 2.45 GHz band microwave sensor design is introduced to be utilized for the dielectric constant determination of ethanol-water solutions. The introduced microwave sensor is composed of two symmetrically positioned, directly coupled inter-connected split-ring resonators with a circular ring-shaped detection area in the middle region, into which a small amount of ethanol-water solution is dropped. The fabricated prototype of the microwave sensor has a total component size of 12 mm x 30 mm on Rogers RO4003 substrate. The sensor measurement performance is numerically evaluated and experimentally validated in good agreement. The introduced microwave sensor has the structural design novelty of possessing the main detection region in a form of a circular hollow where a disposable 3D printed fluid cup can be accommodated for multiple uses. The introduced microwave sensor has technical feasibility to be used as an ingredient identification device for the chemical solutions to figure out complex dielectric parameters of ethanol-water specimens with small, low-cost, reusable, easy-to-fabricate features as well as the determination of volume percentage concentration of ethanol content.

In this paper, a novel machine learning assisted microwave sensor is introduced for the dielectric parameter characterization of ethanol liquid samples with different ingredient concentrations. The proposed sensor is designed with structural geometry of two intercoupled spiral resonators on Rogers RO4003 substrate in band stop filter configuration. The fabricated prototype has overall physical size of 15 mm x 20 mm in 1.8 GHz frequency band. The quantitative sensing performance is numerically analyzed and experimentally verified with the result of good agreement in between. One design novelty in the proposed microwave sensor is that the middle part of main sensing unit is empty for a disposable 3D printed cap to be placed into. These results minor amount of liquid samples to be dropped without the requirement of whole microwave sensor circuit to be replaced for each sample measurement. The liquid samples dropped into the middle part of microwave sensor change the stop band frequency, which is the main parameter to be correlated to dielectric parameters of liquid samples. The proposed microwave sensor has technical potential to be utilized as quality benchmarking equipment for ethanol samples in a compact size with low cost, high sensitivity, reusable, easy fabrication, and machine learning assisted operability features.

This article proposes a novel rectenna design based on modified Hilbert fractal shaped microstrip antenna and Villard voltage doubler rectifying circuit for RF energy harvesting applications operating at Global System for Mobile Communications (GSM) 900 MHz band. The energy harvesting antenna is numerically optimized and fabricated on a Rogers RO4003 substrate of thickness 1.52 mm with a compact overall physical sizes of 80 mm × 82 mm (λ₀/4.16 × λ₀/4.06). Various geometric parameters and circuit component values of the proposed energy harvesting system are optimized in order to achieve a matched input impedance with good radiation performance of high gain for the input power level less than −20 dBm. The numerical and experimental results point out the technical potential of the proposed rectenna design to be utilized in DC power supply modules of low voltage, low power electronic devices.