High Sensitivity Electrical Properties Measurement of Graphene-based Composites using Interferometric Near-field Microwave Technique

High sensitivity electrical properties measurement of composite materials using an interferometric near-field microwave technique is proposed in this paper. A one-port calibration model is developed to relate the measured transmission coefficient to the local properties of the material. To represent the probe-composite sample interaction, an electrical model based on lumped elements is developed. As a demonstration, complex permittivity and conductivity of composite materials prepared with polyvinyl chloride (PVC) and different concentration of graphene are experimentally determined at 2.45 GHz. The obtained results show that the proposed technique is sensitive for the detection of small contrast of permittivity and conductivity in composite material. When graphene concentration increases from 1 to 30%, the conductivity increases from 0.0061 s/m to 0.056 s/m.

Ultra-low profile solar-cell-integrated antenna with a high form factor

This paper presents an ultra-low-profile copper indium gallium selenide (CIGS) based solar cell integrated antenna with a high form factor. A tiny slot was etched from the solar cell to develop an ultra-low-profile solar-cell-integrated antenna. This tiny slot increases the form factor due to the small clearance area from the solar cell. A ground-radiation antenna design method was applied in which lumped elements were employed inside the tiny slot for antenna operation. Another substrate was used under the solar cell for designing the feeding structure with lumped elements connected to the tiny slot using via holes. A prototype was fabricated and measured to verify the operation of a built-in solar-cell antenna and validate the simulated results. The measured results demonstrate that the solar-cell-integrated antenna covers the entire frequency range of the Industrial Scientific Medical band, from 2.4 to 2.5 GHz, with a maximum gain of 2.79 dBi and radiation efficiency higher than 80% within the impedance bandwidth range. Moreover, the proposed design has an ultra-low-profile structure of only 0.0046 λo, where λo represents the free space wavelength at 2.45 GHz, and a high form factor of 99.1% with no optical blockage. The antenna and solar cell were designed to avoid affecting the performance of each other using the radio-frequency decoupler.

Compact dual-band RF rectifier for wireless energy harvesting using CRLH technique

<p>In this paper, a new dual-band radio frequency (RF) rectifier was designed. The proposed design is a low-profile structure with dimensions of <br /> 5×5.5 mm² owing to the use of lumped elements rather than the conventional transmission lines which occupy large footprints. This property can be potentially exploited to use the proposed rectifier in high dense rectenna arrays to generate high output direct current (DC) voltages. Furthermore, the proposed design adopts the composite right/left-handed composite right left-handed (CRLH) technique to realize the dual-band structure at frequencies of 1.8 and 2.4 GHz. Afterward, the matching circuit was optimized to make sure that it offers good matching. The frequency response shows good matching at both bands which are about -22 and -25 dB respectively. Eventually, the simulated circuit has a conversion efficiency of 52% and output voltages of 0.5 V at -5 dBm for the two bands.</p>

Ultra-Low Profile Solar-Cell-Integrated Antenna With a High Form Factor

This paper presents an ultra-low-profile copper indium gallium selenide (CIGS) based solar cell integrated antenna with a high form factor. A tiny slot was etched from the solar cell to develop an ultra-low-profile solar-cell-integrated antenna. This tiny slot increases the form factor due to the small clearance area from the solar cell. A ground-radiation antenna design method was applied in which lumped elements were employed inside the tiny slot for antenna operation. Another substrate was used under the solar cell for designing the feeding structure with lumped elements connected to the tiny slot using via holes. A prototype was fabricated and measured to verify the operation of a built-in solar-cell antenna and validate the simulated results. The measured results demonstrate that the solar-cell-integrated antenna covers the entire frequency range of the Industrial Scientific Medical band from 2.4 to 2.5 GHz with good performance characteristics. The proposed design has a low-profile structure with high optical transparency for solar cells. The antenna and solar cell were designed to avoid affecting the performance of each other using the radio-frequency decoupler.

Electrical analogs of curved beams and application to piezoelectric network damping

In this paper, the method of electric analog synthesis is applied to design a piezo-electro-mechanical arch able to show the capacity of multimodal damping. An electric-analog circuit is designed by using a finite number of lumped elements representing the equivalent of a curved beam. Spatial and frequency coherence conditions are proven to be verified for the modes to be damped: in fact, lumped-element circuit can damp only a finite number of vibration modes. Analogous boundary conditions are ensured, so that natural frequencies and mode shapes of both the curved beam and the analog circuit are equal. The instance considered here is the vibration mitigation of a piezo-electro-mechanical arch. Having a view towards prototypical applications, all simulations consider values of physically feasible passive circuital elements. It is believed that the present results may represent a step towards the design of multi-physics metamaterials based on micro-structures exploiting the principle of multimodal damping.

Investigation of Broadband Printed Biconical Antenna with Tapered Balun for EMC Measurements

This article investigates the design, modeling, and fabrication of small-size (150 × 90 × 1.6 mm) broadband printed biconical antenna. The proposed antenna is intended for use a reference antenna for electromagnetic interference measurement inside the EMC chamber. The reflection coefficient (S11-parameter) is verified by modeling the equivalent circuit of the structure in terms of lumped elements. This structure offers a −10 dB impedance bandwidth (from 0.65 GHz to 2.3 GHz) with the tapered balun feeding method. Therefore, it has a high probability of estimating the electromagnetic waves emitted from several applications such as GSM, LTE, UMTS, 3G, Wi-fi, Bluetooth, ZigBee and more. The simulated standard antenna parameters are compatible with the measured parameters results. Furthermore, azimuth omnidirectional radiation pattern and well-realized gain (3.8 dBi) are achieved, reflecting good values of antenna factor compared to the commercial design.

Electrically Reconfigurable Microwave Metasurfaces With Active Lumped Elements: A Mini Review

Metasurfaces, a kind of two-dimensional artificially engineered surfaces consist of subwavelength unit cells, have recently attracted tremendous attention, owing to their exotic abilities for tailoring electromagnetic responses. With active lump elements incorporated into the design of metasurfaces, dynamic reconfigurabilities enabled by external stimuli could be realized, offering opportunities for the dynamic manipulation of electromagnetic waves. In this mini review, we present a brief review on the recent progress of electrically reconfigurable metasurfaces at microwave frequencies. A brief discussion will also be given with our outlook on future development direction and possible challenges in this interesting field.