Experimental Characterization of 2 × 2 Electronically Reconfigurable Polarization Converter Unit Cells at X-Band

In this paper, an electronically reconfigurable polarization converter unit cell operating at X-band is proposed. The polarization converter unit cell consists of a passive patch, a phase shifter, and an active patch. There are two PIN diodes on the active patch. By switching the bias conditions of those PIN diodes, an electronically reconfigurable polarization converter is conceived. Both the passive and active patches are circular, and there are circular types of slots on both patches to enhance the operating bandwidth. To compensate for the capacitance introduced by PIN diodes, an equivalent capacitance structure is introduced on the active patch. 2 × 2 unit cells are designed to check the performance of the unit cell for polarization conversion applications. In addition, a novel type of experimental characterization technique is proposed to check the performance of polarization conversion using 2 × 2 unit cells. Two WR-90 waveguide sections, two rectangular to square sections, and a power supply are taken for the measurements. The rectangular to square waveguide transition section is designed in such a way so that 2 × 2 unit cells can be perfectly adjusted on the transition section and the performance of the 2 × 2 unit cells can be measured. The simulation results of the 8 × 8 array are also added to a miniaturized X-band horn antenna to check the performance of the overall array.

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Experimental Characterization of 2 × 2 Electronically Reconfigurable 1 Bit Unit Cells for a Beamforming Transmitarray at X Band

Journal of Electromagnetic Engineering and Science ◽

10.26866/jees.2021.21.2.153 ◽

2021 ◽

Vol 21 (2) ◽

pp. 153-160

Author(s):

Biswarup Rana ◽

In-Gon Lee ◽

Ic-Pyo Hong

Keyword(s):

Phase Shifter ◽

Unit Cell ◽

Experimental Characterization ◽

Waveguide Transition ◽

Transmitted Waves ◽

X Band ◽

Unit Cells ◽

New Type ◽

Good Agreement

This paper proposes a reconfigurable unit cell for a transmitarray operating at the X band. The unit cell consists of an active patch, a passive patch, and a phase shifter. The active patch has two PIN diodes that change the phase of 180° of the transmitted waves. The passive and active patches both have circular slots to enhance the bandwidth of the transmitted wave. We also propose a new type of experimental characterization technique to measure the performance of the unit cells at the X band without fabricating the entire transmitarray. Instead of a 1 unit cell as described in the literature, we propose 2 × 2 unit cells to measure the performance of unit cells using the X band waveguide. The waveguide consists of a WR-90 section and a rectangular to square waveguide transition section that can be fit to our proposed structure. A good agreement between simulated and measured results was found.

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Simple design of efficient broadband multifunctional polarization converter for X-band applications

Scientific Reports ◽

10.1038/s41598-021-81586-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Thi Kim Thu Nguyen ◽

Thi Minh Nguyen ◽

Hong Quang Nguyen ◽

Thanh Nghia Cao ◽

Dac Tuyen Le ◽

...

Keyword(s):

Circular Polarization ◽

Incident Angle ◽

Polarization Conversion ◽

Simple Design ◽

Cross Polarization ◽

Polarization Converter ◽

Frequency Bands ◽

X Band ◽

Cost Efficient ◽

Patch Resonators

AbstractA simple design of a broadband multifunctional polarization converter using an anisotropic metasurface for X-band application is proposed. The proposed polarization converter consists of a periodic array of the two-corner-cut square patch resonators based on the FR-4 substrate that achieves both cross-polarization and linear-to-circular polarization conversions. The simulated results show that the polarization converter displays the linear cross-polarization conversion in the frequency range from 8 to 12 GHz with the polarization conversion efficiency above 90%. The efficiency is kept higher than 80% with wide incident angle up to 45°. Moreover, the proposed design achieves the linear-to-circular polarization conversion at two frequency bands of 7.42–7.6 GHz and 13–13.56 GHz. A prototype of the proposed polarization converter is fabricated and measured, showing a good agreement between the measured and simulated results. The proposed polarization converter exhibits excellent performances such as simple structure, multifunctional property, and large cost-efficient bandwidth and wide incident angle insensitivity in the linear cross polarization conversion, which can be useful for X-band applications. Furthermore, this structure can be extended to design broadband polarization converters in other frequency bands.

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X-band Band-pass Frequency Selective Surface for Radome Applications

TELKOMNIKA Indonesian Journal of Electrical Engineering ◽

10.11591/tijee.v16i2.1613 ◽

2015 ◽

Vol 16 (2) ◽

pp. 281

Author(s):

Tariq Rahim ◽

Jiodong Xu

Keyword(s):

Frequency Selective Surface ◽

Unit Cell ◽

Dielectric Substrates ◽

Low Profile ◽

X Band ◽

Analysis And Synthesis ◽

Unit Cells ◽

Band Pass ◽

Frequency Selective ◽

Unit Cell Dimensions

A low profile multi layer miniaturized unit cell frequency selective surface (FSS) with second-order band-pass response is design. The metallic layers in the form of capacitive patches and inductive grids are separated by dielectric substrates. The non-resonant sub-wavelength unit cells with unit cell dimensions and periodicities on the order of 0.15λ. The overall thickness of approximately 0.03λ is designed which is useful at lower frequencies with long wavelengths. The FSS exhibit a stable frequency response to different angles of incidence and polarizations. The analysis and synthesis of the FSS is done using equivalent circuit method and simulated using CST microwave studio at X-band.

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Ternary optimization for designing metasurfaces

Scientific Reports ◽

10.1038/s41598-021-96564-5 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Azin Hojjati ◽

Mohammad Soleimani ◽

Vahid Nayyeri ◽

Omar M. Ramahi

Keyword(s):

Design Method ◽

Pso Algorithm ◽

Frequency Selective Surface ◽

Unit Cell ◽

Polarization Conversion ◽

Proof Of Concept ◽

Polarization Converter ◽

Swarm Optimization ◽

Via Hole ◽

Comparison Of The Results

AbstractA fully automated approach for designing metasurfaces whose unit cell may include metallic vias is proposed. Towards this aim, a ternary version of the particle swarm optimization (PSO) algorithm is employed in order to find the optimal metallic pattern and via-hole positions simultaneously. In the proposed design method, the upper surface of the unit cell is first pixelated. One of the possible three states of a metallic covered pixel, an uncovered etched pixel and a pixel containing a centered metalized via-hole is assigned to each pixel. The optimal state of each pixel is then determined by utilizing a ternary PSO algorithm to achieve favorable design goals. This method can be used for designing various metasurfaces as well as other via-assisted electromagnetic structures. As a proof of concept, the proposed method was applied to design two surfaces: a frequency selective surface with a minimum resonance frequency, and a linear-to-circular polarization converter with a maximum polarization conversion bandwidth. Comparison of the results with previous works confirms the efficiency and capability of the proposed method to design diverse metasurfaces in an automated fashion without the need for any theoretical or physical model.

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1-Bit Reconfigurable Unit Cell Based on PIN Diodes for Transmit-Array Applications in $X$-Band

IEEE Transactions on Antennas and Propagation ◽

10.1109/tap.2012.2189716 ◽

2012 ◽

Vol 60 (5) ◽

pp. 2260-2269 ◽

Cited By ~ 67

Author(s):

Antonio Clemente ◽

Laurent Dussopt ◽

Ronan Sauleau ◽

Patrick Potier ◽

Philippe Pouliguen

Keyword(s):

Unit Cell ◽

Pin Diodes ◽

X Band

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Bayesian removal of noise for increased sensitivity in vector pattern recognition lattice imaging of interfaces

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100150800 ◽

1993 ◽

Vol 51 ◽

pp. 994-995

Author(s):

L. Fei ◽

P. Fraundorf

Keyword(s):

Pattern Recognition ◽

Perfect Crystal ◽

Unit Cell ◽

Ion Milling ◽

Beam Radiation ◽

Major Interest ◽

Unit Cells ◽

Mapping Process ◽

Increased Sensitivity ◽

Electron Microscopes

Interface structure is of major interest in microscopy. With high resolution transmission electron microscopes (TEMs) and scanning probe microscopes, it is possible to reveal structure of interfaces in unit cells, in some cases with atomic resolution. A. Ourmazd et al. proposed quantifying such observations by using vector pattern recognition to map chemical composition changes across the interface in TEM images with unit cell resolution. The sensitivity of the mapping process, however, is limited by the repeatability of unit cell images of perfect crystal, and hence by the amount of delocalized noise, e.g. due to ion milling or beam radiation damage. Bayesian removal of noise, based on statistical inference, can be used to reduce the amount of non-periodic noise in images after acquisition. The basic principle of Bayesian phase-model background subtraction, according to our previous study, is that the optimum (rms error minimizing strategy) Fourier phases of the noise can be obtained provided the amplitudes of the noise is given, while the noise amplitude can often be estimated from the image itself.

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Prediction of Effective Thermal Conductivities of Four-Directional Carbon/Carbon Composites by Unit Cells with Different Sizes

Applied Sciences ◽

10.3390/app11031171 ◽

2021 ◽

Vol 11 (3) ◽

pp. 1171

Author(s):

Chang Xu ◽

Zhihong Sun ◽

Guowei Shao

Keyword(s):

Carbon Fiber ◽

Longitudinal Direction ◽

Unit Cell ◽

Carbon Composites ◽

Temperature Boundary ◽

The Matrix ◽

Unit Cells ◽

Experimental Values ◽

Different Diameters ◽

Thermal Conductivities

Two-unit cells developed to predict the effective thermal conductivities of four-directional carbon/carbon composites with the finite element method are proposed in this paper. The smaller-size unit cell is formulated from the larger-size unit cell by two 180° rotational transformations. The temperature boundary conditions corresponding to the two-unit cells are derived, and the validity is verified by the temperature and heat flux distributions at specific positions of the larger-size unit cell and the smaller-size unit cell. The thermal conductivities of the carbon fiber bundles and carbon fiber rods are measured firstly. Then, combined with the properties of the matrix, the effective thermal conductivities of the four-directional carbon/carbon composites are numerically predicted. The results in transverse direction predicted by the larger-size unit cell and the smaller-size unit cell are both higher than experimental values, which are 5.8 to 6.2% and 7.3 to 8.2%, respectively. In longitudinal direction, the calculated thermal conductivities of the larger-size unit cell and the smaller-size unit cell are 6.8% and 6.2% higher than the experimental results, respectively. In addition, carbon fiber rods with different diameters are set to clarify the influence on the effective thermal conductivities of the four-directional carbon/carbon composites.

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A Multiband Antenna Stacked with Novel Metamaterial SCSRR and CSSRR for WiMAX/WLAN Applications

Micromachines ◽

10.3390/mi12020113 ◽

2021 ◽

Vol 12 (2) ◽

pp. 113

Author(s):

Rajiv Mohan David ◽

Mohammad Saadh AW ◽

Tanweer Ali ◽

Pradeep Kumar

Keyword(s):

Split Ring Resonator ◽

Unit Cell ◽

Ring Resonators ◽

Split Ring ◽

Medium Theory ◽

High Frequency Structure Simulator ◽

Dimension Analysis ◽

Unit Cells ◽

Coaxial Feed ◽

Triple Band

This paper presents an innovative method for the design of a triple band meta-mode antenna. This unique design of antenna finds application in a particular frequency band of WLAN and WiMAX. This antenna comprises of a square complimentary split ring resonator (SCSRR), a coaxial feed, and two symmetrical comb shaped split ring resonators (CSSRR). The metamaterial unit cell SCSRR independently gains control in the band range 3.15–3.25 GHz (WiMAX), whereas two symmetrical CSSRR unit cell controls the band in the ranges 3.91–4.01 GHz and 5.79–5.94 GHz (WLAN). This design methodology and the study of the suggested unit cells structure are reviewed in classical waveguide medium theory. The antenna has a miniaturized size of only 0.213λ0 × 0.192λ0 × 0.0271λ0 (20 × 18 × 2.54 mm3, where λ0 is the free space wavelength at 3.2 GHz). The detailed dimension analysis of the proposed antenna and its radiation efficiency are also presented in this paper. All the necessary simulations are carried out in High Frequency Structure Simulator (HFSS) 13.0 tool.

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Dynamic crushing behavior of closed-cell aluminum foams based on different space-filling unit cells

Archives of Civil and Mechanical Engineering ◽

10.1007/s43452-021-00251-1 ◽

2021 ◽

Vol 21 (3) ◽

Author(s):

S. Talebi ◽

R. Hedayati ◽

M. Sadighi

Keyword(s):

Surface Area ◽

Dynamic Behavior ◽

Energy Absorption ◽

Peak Stress ◽

Absorption Capacity ◽

Unit Cell ◽

Lattice Structures ◽

Energy Absorption Capacity ◽

Closed Cell ◽

Unit Cells

AbstractClosed-cell metal foams are cellular solids that show unique properties such as high strength to weight ratio, high energy absorption capacity, and low thermal conductivity. Due to being computation and cost effective, modeling the behavior of closed-cell foams using regular unit cells has attracted a lot of attention in this regard. Recent developments in additive manufacturing techniques which have made the production of rationally designed porous structures feasible has also contributed to recent increasing interest in studying the mechanical behavior of regular lattice structures. In this study, five different topologies namely Kelvin, Weaire–Phelan, rhombicuboctahedron, octahedral, and truncated cube are considered for constructing lattice structures. The effects of foam density and impact velocity on the stress–strain curves, first peak stress, and energy absorption capacity are investigated. The results showed that unit cell topology has a very significant effect on the stiffness, first peak stress, failure mode, and energy absorption capacity. Among all the unit cell types, the Kelvin unit cell demonstrated the most similar behavior to experimental test results. The Weaire–Phelan unit cell, while showing promising results in low and medium densities, demonstrated unstable behavior at high impact velocity. The lattice structures with high fractions of vertical walls (truncated cube and rhombicuboctahedron) showed higher stiffness and first peak stress values as compared to lattice structures with high ratio of oblique walls (Weaire–Phelan and Kelvin). However, as for the energy absorption capacity, other factors were important. The lattice structures with high cell wall surface area had higher energy absorption capacities as compared to lattice structures with low surface area. The results of this study are not only beneficial in determining the proper unit cell type in numerical modeling of dynamic behavior of closed-cell foams, but they are also advantageous in studying the dynamic behavior of additively manufactured lattice structures with different topologies.

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C-Band and X-Band Switchable Frequency-Selective Surface

Electronics ◽

10.3390/electronics10040476 ◽

2021 ◽

Vol 10 (4) ◽

pp. 476

Author(s):

Umer Farooq ◽

Adnan Iftikhar ◽

Muhammad Farhan Shafique ◽

Muhammad Saeed Khan ◽

Adnan Fida ◽

...

Keyword(s):

Bottom Layer ◽

Frequency Selective Surface ◽

Transverse Magnetic ◽

Unit Element ◽

Angular Stability ◽

Band Spectrum ◽

Pin Diode ◽

Pin Diodes ◽

X Band ◽

Frequency Selective

This paper presents a highly compact frequency-selective surface (FSS) that has the potential to switch between the X-band (8 GHz–12 GHz) and C-band (4 GHz–8 GHz) for RF shielding applications. The proposed FSS is composed of a square conducting loop with inward-extended arms loaded with curved extensions. The symmetric geometry allows the RF shield to perform equally for transverse electric (TE), transverse magnetic (TM), and 45° polarizations. The unit cell has a dimension of 0.176 λ0 and has excellent angular stability up to 60°. The resonance mechanism was investigated using equivalent circuit models of the shield. The design of the unit element allowed incorporation of PIN diodes between adjacent elements for switching to a lower C-band spectrum at 6.6 GHz. The biasing network is on the bottom layer of the substrate to avoid effects on the shielding performance. A PIN diode configuration for the switching operation was also proposed. In simulations, the PIN diode model was incorporated to observe the switchable operation. Two prototypes were fabricated, and the switchable operation was demonstrated by etching copper strips on one fabricated prototype between adjacent unit cells (in lieu of PIN diodes) as a proof of the design prototypes. Comparisons among the results confirmed that the design offers high angular stability and excellent performance in both bands.

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