scholarly journals Design and development of a multi-functional bi-anisotropic metasurface with ultra-wide out of band transmission

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fahad Ahmed ◽  
Tania Tamoor ◽  
Tayyab Hassan ◽  
Nosherwan Shoaib ◽  
Akram Alomainy ◽  
...  
Keyword(s):  
Cross Section ◽  
Electromagnetic Compatibility ◽  
State Of The Art ◽  
Transmission Characteristics ◽  
Wave Trapping ◽  
Beam Splitters ◽  
X Band ◽  
Fabry Perot ◽  
Polarization Insensitive ◽  
L Band

AbstractThis paper presents a multi-functional bi-anisotropic metasurface having ultra-wide out of band transmission characteristics. The proposed metasurface is comprised of 90° rotated T-shaped configuration yielding greater than or equal to 50% out-of-band transmission from above L- to X-band. Moreover, this metasurface achieves a maximum of 99% out-of-band transmission at lower frequency bands (i.e., L-band). The simultaneous absorptive and controlled reflection functionalities are achieved at 15.028 to 15.164 GHz along with polarization-insensitive and angular stable properties. The proposed metasurface yields state-of-the-art features compared to already published papers and has broader scope for Fabry Perot cavity, Radar cross-section (RCS) reduction, electromagnetic compatibility and interference (EMC/I) shielding, selective multi-frequency bolometers, ultrathin wave trapping filters, sensors and beam-splitters in the microwave domain.

scholarly journals Low-RCS, Circular Polarization, and High-Gain Broadband Antenna Based on Mirror Polarization Conversion Metasurfaces

2019 ◽  
Vol 2019 ◽  
pp. 1-8 ◽  
Author(s):  
Liang Zhang ◽  
Changqing Liu ◽  
Chun Ni ◽  
Meng Kong ◽  
Xianliang Wu
Keyword(s):  
Circular Polarization ◽  
Antenna Array ◽  
Cross Section ◽  
High Gain ◽  
Slot Antenna ◽  
Polarization Conversion ◽  
Broadband Antenna ◽  
X Band ◽  
Fabry Perot ◽  
Operating Bandwidth

In this paper, a novel slot antenna array that is based on mirror polarization conversion metasurfaces (MPCM) is proposed. It achieves circular polarization (CP) and effectively reduces the radar cross section (RCS) and increases gain in the entire x-band. This design uses the mirrored composition of the polarization conversion metasurfaces (PCM) on the top surface of the substrate. The MPCM covers a 2 × 2 slot antenna array that is fed with by a sequentially rotating network. The CP radiation is realized by the polarization conversion characteristics of the PCM. At the same time, the reduction of RCS is achieved by 180° (±30°) reflection phase difference between two adjacent PCMs. The improvement in gain is achieved by using a Fabry–Perot cavity, which is constituted by the ground of the antenna and the PCM. Simulated and measured results show that approximately 46.4% of the operating bandwidth is in the range of 7.5–12 GHz (AR < 3 dB) and the gain of the antenna with MPCM is at least 5 dB higher than the reference antenna. Moreover, the monostatic RCS is reduced from 8 to 20 GHz.

scholarly journals A Classification Scheme for Sediments and Habitats on Exposed Intertidal Flats with Multi-Frequency Polarimetric SAR

2021 ◽  
Vol 13 (3) ◽  
pp. 360
Author(s):  
Wensheng Wang ◽  
Martin Gade ◽  
Kerstin Stelzer ◽  
Jörn Kohlus ◽  
Xinyu Zhao ◽  
...  
Keyword(s):  
Classification Scheme ◽  
Wadden Sea ◽  
Relative Difference ◽  
Polarimetric Synthetic Aperture Radar ◽  
Intertidal Flats ◽  
Sediment Types ◽  
X Band ◽  
Good Potential ◽  
L Band ◽  
Sar Data

We developed an extension of a previously proposed classification scheme that is based upon Freeman–Durden and Cloude–Pottier decompositions of polarimetric Synthetic Aperture Radar (SAR) data, along with a Double-Bounce Eigenvalue Relative Difference (DERD) parameter, and a Random Forest (RF) classifier. The extension was done, firstly, by using dual-copolarization SAR data acquired at shorter wavelengths (C- and X-band, in addition to the previously used L-band) and, secondly, by adding indicators derived from the (polarimetric) Kennaugh elements. The performance of the newly developed classification scheme, herein abbreviated as FCDK-RF, was tested using SAR data of exposed intertidal flats. We demonstrate that the FCDK-RF scheme is capable of distinguishing between different sediment types, namely mud and sand, at high spatial accuracies. Moreover, the classification scheme shows good potential in the detection of bivalve beds on the exposed flats. Our results show that the developed FCDK-RF scheme can be applied for the mapping of sediments and habitats in the Wadden Sea on the German North Sea coast using multi-frequency and multi-polarization SAR from ALOS-2 (L-band), Radarsat-2 (C-band) and TerraSAR-X (X-band).

Investigation of X-band backscattering from wave breaking in a laboratory experiment

2021 ◽  
Author(s):  
Nikita Rusakov ◽  
Georgy Baidakov ◽  
Evgeny Poplavsky ◽  
Yuliya Troitskaya ◽  
Maksim Vdovin
Keyword(s):  
Cross Section ◽  
Wave Breaking ◽  
Spectral Characteristics ◽  
Wave Number ◽  
Scattered Signal ◽  
Channel Cross Section ◽  
Frequency Wave ◽  
First Case ◽  
X Band ◽  
Working Section

&lt;p&gt;The work is concerned with the study of the breaking surface wave effect on the intensity and spectral characteristics of a scattered radar signal in laboratory conditions.&lt;/p&gt;&lt;p&gt;&lt;span&gt;The experiments were carried out on the reconstructed TSWiWaT wind wave flume of the IAP RAS. The channel is 12 m long, the channel cross-section varies from 0.7 x 0.7 m at the entrance to 0.7 x 0.9 m in the working section at a distance of 9 m. The airflow speed on the axis is 3-35 m/s, which corresponds to the values of the wind speed U&lt;/span&gt;&lt;sub&gt;10&lt;/sub&gt;&lt;span&gt; of 11-50 m/s.&lt;/span&gt;&lt;/p&gt;&lt;p&gt;The wave characteristics in the flume were measured by an array of three wave gauges positioned in the corners of an equal-side triangle with 2.5 cm side, the data sampling rate was 200 Hz. Such a system gives the opportunity to retrieve 3D frequency-wave number spectra of surface waves.&lt;/p&gt;&lt;p&gt;The airflow parameters were measured using the profiling method. The velocity profiles were measured in the working section using an S-shaped Pitot tube. Microwave measurements were carried out using an X-band coherent Doppler scatterometer with a wavelength of 3.2 cm with sequential reception of linear polarizations.&amp;#160; The absolute value of the radar cross-section (RCS) on the wavy water surface was determined by comparing the scattered signal with the signal reflected from the calibrator with a known value of the RCS - a metal ball with a diameter of 6 cm. The dimensions of the observation cross-section were 40 cm x 40 cm, the incidence angles were 30&amp;#176;, 40&amp;#176;, 50&amp;#176; for the upwind direction, the distance to the target was 3.15 m.&lt;/p&gt;&lt;p&gt;Two series of experiments were carried out. In the first case, wind waves on the surface of pure deep water, developing under the action of a fan generated wind, were studied. In the second case, a train of three waves was generated at the beginning of the channel, with the fan turned on, in order to simulate shallow water an inclined plate was placed under water in front of the measurement area. As a result, the breaking waves occurred at a fixed point and at weaker winds compared to the first case.&lt;/p&gt;&lt;p&gt;As a result, an increase in the scattered signal intensity during artificial wave breaking in the case of weak winds was noted. For strong winds, the effect turned out to be insignificant, despite the increased amplitude of the waves under study. The Doppler spectra analysis is also presented.&lt;/p&gt;&lt;p&gt;This work was supported by the RFBR projects No. 19-05-00249, 19-05-00366. &amp;#160;&lt;/p&gt;

A Novel Low Profile Polarization Insensitive Electromagnetic Shield for X-Band Applications

2021 ◽  
Author(s):  
Muhammad Idrees ◽  
Sai-Wai Wong ◽  
Yejun He ◽  
Saifullah Khalid ◽  
Muhammad Ali Khalid ◽  
...  
Keyword(s):  
Low Profile ◽  
X Band ◽  
Electromagnetic Shield ◽  
Polarization Insensitive
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