A multifunctional reconfigurable metasurface based on liquid metal injection is presented. The reflective flexible material metasurface formed by two switchable microfluidic layers&#x2014; the top layer comprising an array of meandered half-rings and the lower layer, straight meander lines&#x2014;can be reconfigured into four states. The proposed metasurface becomes a reflector with emptied channels, whereas it exhibits linear-to-circular polarization conversion (or linear-to-cross-polarization conversion) properties when the top (or bottom) layer is filled with a liquid metal alloy. Upon normal excitation of linearly u/v-polarized waves and activation of the bottom layer, the metasurface reflects cross v/u-polarized waves in the frequencies from 9.83 to 17.42 GHz (53&#x0025; bandwidth) with a polarization conversion ratio (PCR) of at least 90&#x0025;. On the other hand, the metasurface operates as a linear-to-circular polarizer (for u/v-polarized waves) over 8.97&#x2013;11.30 GHz (23&#x0025; bandwidth), reflecting left- or right-hand circularly polarized waves. To verify the polarization conversion performance, a <inline-formula> <tex-math notation="LaTeX">$25\times 25$ </tex-math></inline-formula> element metasurface array is fabricated and measured. The experimental results confirm the simulation results over the 8&#x2013;12 GHz test band. The compactness, structural flexibility, and multifunctionality of the proposed metasurface make it a suitable candidate for modern integrated antenna array systems. 

Reconfigurable Polarization Converter Using Liquid Metal Based Metasurface

A novel high-efficiency polarization-selective bifunctional metasurface (MS) is proposed, which can realize cross-polarized focusing transmission for left-handed circular polarization (LHCP) incidence and co-polarized specular reflection for right-handed circular polarization (RHCP) incidence. As an example of its practical application, the designed MS is applied to form an RHCP folded transmitarray antenna (FTA) whose feed source (FS) is integrated with the bottom metallic surface. To prove the concept, a prototype of millimeter-wave (MMW) FTA based on the proposed MS is numerically simulated, physically implemented, and experimentally measured. The measured results coincide well with the simulated ones, showing a peak gain of 23.6 dBi at 27.7 GHz with the peak aperture efficiency of 43.1%, a 3 dB gain bandwidth of 15.8% (25–29.3 GHz), and a 3 dB axial-ratio (AR) bandwidth over 29.6%. The proposed high-performance antenna has the advantages of low profile, high efficiency, integration design, and broad bandwidth, which may have promising applications in the fifth-generation MMW communication system. The proposed MS and its application to high-gain antenna may promote the uses of MS to real-world applications in satellite communication, radar detection, and wireless communication. 

Polarization-Selective Bifunctional Metasurface for High-Efficiency Millimeter-Wave Folded Transmitarray Antenna With Circular Polarization

A novel high-efficiency polarization-selective bifunctional metasurface (MS) is proposed which can realize cross-polarized focusing transmission for left-handed circular polarization (LHCP) incidence while co-polarized specular reflection for right-handed circular polarization (RHCP) incidence. As an example of its practical application, the designed MS is applied to form a RHCP folded transmitarray antenna (FTA) whose feed source is integrated with the bottom metallic surface. To prove the concept, a prototype of millimeter-wave FTA based on the proposed MS are numerically simulated, physically implemented, and experimentally measured. The measured results coincide well with the simulated ones, showing a peak gain of 23.6 dBi at 27.7 GHz with the peak aperture efficiency of 43.1%, a 3 dB gain bandwidth of 15.8% (25 -29.3 GHz), and a 3 dB axial-ratio (AR) bandwidth over 29.6%. The proposed high-performance antenna has the advantages of low profile, high efficiency, integration design, broad bandwidth, which may have promising applications in the fifth-generation millimeter-wave communication system. The proposed MS and its application to high-gain antenna may promote the uses of MS to real-world applications in satellite communication, radar detection, and wireless communication.

Polarization-Selective Bifunctional Metasurface for High-Efficiency Millimeter-wave Folded Transmitarray Antenna with Circular Polarization

This paper presents the analysis and design of an X-band reflectarray. The proposed antenna can be used for a medium Earth orbit (MEO) remote sensing satellite system in the 8.5 GHz band. To obtain a nearly constant response along the coverage area of this satellite system, the proposed antenna was designed with a flat-top radiation pattern with a beam width of around 29° for the required MEO system. In addition, broadside pencil beam and tilted pencil beam reflectarrays were also investigated. The feeding element of the proposed reflectarray antennas is a Yagi–Uda array. The amplitude and phase distribution of the fields due to the feeding element on the aperture of the reflectarray antenna are obtained directly by numerical simulation without introducing any approximation. The required phase distribution along the aperture of the reflectarray to obtain the required flat-top radiation pattern is obtained using the genetic algorithm (GA) optimization method. The reflecting elements of the reflectarray are composed of stacked circular patches. This stacked configuration was found to be appropriate for obtaining a wide range of reflection phase shift, which is required to implement the required phase distribution on the reflectarray aperture. The antenna was fabricated and measured for verification.

/pdf/analysis-and-design-of-an-x-band-reflectarray-antenna-for-ly5tl12p.pdf

Analysis and Design of an X-Band Reflectarray Antenna for Remote Sensing Satellite System

The micro-electromechanical system (MEMS) sensors are suitable devices for vibrational analysis in complex systems. The Fabry–Pérot interferometer (FPI) is used due to its high sensitivity and immunity to electromagnetic interference (EMI). Here, we present the design, fabrication, and characterization of a silicon-on-insulator (SOI) MEMS device, which is embedded in a metallic package and connected to an optical fiber. This integrated micro-opto-electro-mechanical system (MOEMS) sensor contains a mass structure and handle layers coupled with four designed springs built on the device layer. An optical reading system using an FPI is used for displacement interrogation with a demodulation technique implemented in LabVIEW®. The results indicate that our designed MOEMS sensor exhibits a main resonant frequency of 1274 Hz with damping ratio of 0.0173 under running conditions up to 7 g, in agreement with the analytical model. Our experimental findings show that our designed and fabricated MOEMS sensor has the potential for engineering application to monitor vibrations under high-electromagnetic environmental conditions.

/pdf/design-and-development-of-a-moems-accelerometer-using-soi-babd6tek.pdf

Design and Development of a MOEMS Accelerometer Using SOI Technology

A wideband folded reflectarray antenna (FRA) based on single-layered polarization rotating metasurface (PRM) is proposed. The FRA is composed of a wideband polarization grid (PG), a wideband PRM and a wideband circular waveguide as the primary source. First, a wideband polarization rotating unit cell consisting of rhombus-shaped metal patch etched on dielectric substrate is designed, which can be used to rotate polarization of the reflective wave 90° relative to that of the incident wave. The element and its mirror image can provide 0°, 90°, 180° and 270° phase shifts with 2-bit phase quantization and relatively higher polarization conversion rates in the Ku band. Due to the introduction of PG and PRM, the distance between the PG surface and the feed phase center can be reduced to about 1/2 of the distance between the imaginary feed and PRM reflectarray. Finally, a wideband FRA consisting of 315 elements with circular aperture is designed, fabricated and measured. The measured results indicate that the proposed antenna achieves 39.5% 3-dB gain bandwidth with 25.5 dBi peak gain at 15 GHz. Its maximum aperture efficiency is about 40%. Low-profile and wideband features of the FRA make it be a candidate in the wireless communication systems.

/pdf/a-wideband-folded-reflectarray-antenna-based-on-single-5at1ty5dbv.pdf

A Wideband Folded Reflectarray Antenna Based on Single-Layered Polarization Rotating Metasurface

A method for measuring vibration characteristics of MEMS (Micro Electro Mechanical System) is presented. This method aims to simulate a real environment where MEMS operates. At first, the method of applying high and low temperature in a vacuum environment is studied. And the excitation method applying to movable microstructures of MEMS in this environment is found. Based on the above environmental conditions, the vibration characteristics of MEMS movable microstructure are measured by micro-laser vibration measurement. The base excitation method is used to measure the vibration characteristics of MEMS movable microstructures outside the plane. ANSYS 14.0 was used for finite element simulation to verify this method. The electrostatic excitation method is used to measure the inside of the plane. The stroboscopic method is used to verify the electrostatic excitation by fitting the displacement signal of the movable microstructure and the excitation output signal. The results show that the out-of-plane first-order frequency is 11.926 kHz, and the error is 0.30% compared with the experimental results. The amplitude is 44.218 nm, and the error is 0.59%. The in-plane first-order frequency is 5715.7Hz, which achieves the requirement of design precision. Both the numerical simulation and the stroboscopic method verify the excitation method well. The effect of temperature on the natural frequency of the structure is negatively correlated. And as the temperature drops, the motion of the structure becomes increasingly violent. The findings of this study provide important guidance for maintenance, reliable operation and optimal design of MEMS.

/pdf/vibration-characteristic-measurement-method-of-mems-2a65082z5a.pdf

Vibration Characteristic Measurement Method of MEMS Gyroscopes in Vacuum, High and Low Temperature Environment and Verification of Excitation Method

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A Wideband Folded Reflectarray Antenna Based on Single-Layered Polarization Rotating Metasurface

Vibration Characteristic Measurement Method of MEMS Gyroscopes in Vacuum, High and Low Temperature Environment and Verification of Excitation Method