Vertical Polarization Research Articles

Low‐profile multi‐polarization and pattern reconfigurable antenna based on metasurface

AbstractIn this letter, a low‐profile metasurface (MS) antenna with multi‐polarization and pattern reconfigurability is presented. The antenna mainly consists of two parts, including a loop antenna fed by balun, and a MS antenna excited by the coupled aperture. When switching the PIN diode and rotating the MS, the multi‐polarization and pattern reconfigurable ability of the antenna is obtained. While the loop antenna is excited, a horizontally linear polarized (HLP) wave and omnidirectional pattern are obtained. Besides, when the MS is operated, due to the differential phase between the orthogonal surface impedance components, the antenna can be switched between vertical linear polarization (VLP), left‐hand circular polarization (LHCP), and right‐hand circular polarization (RHCP). Furthermore, the antenna could achieve a directional pattern. As the simulated and measured results shown, the proposed antenna has an overlapped impedance bandwidth (IMBW) of 24.7% for all polarization modes and a 3‐dB axial ratio (AR) bandwidth of 11.8% for L/RHCP modes. Moreover, the antenna owns a low profile of 0.06 λ (under the operating centre frequency).

Metamaterial-Based Low-Profile Broadband In-Band Full-Duplex Antenna

A low-profile wideband antenna with extremely high isolation is proposed for in-band full-duplex applications. It is designed in a coplanar structure with a periodic array of non-uniform metamaterial cells, a hook-like feeding probe, and four mushroom-like structures. The non-uniform metamaterial cells are excited by a hook-like feeding probe to achieve horizontal polarization. Meanwhile, two slots at the end of the ground are coupled with microstrip feed lines for vertical polarization. As a result, leakage currents between two symmetrical feed structures are suppressed to realize high isolation in wide operation bandwidth. Furthermore, four mushroom-like structures are embedded in the corners of the metamaterial cells to improve bandwidth and isolation. Measured results demonstrate that the proposed antenna with a low profile of 0.06 λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the wavelength at the center frequency of the operating band) achieves a -10 dB impedance bandwidth of 24.5% from 3.20 GHz to 4.09 GHz and a high Rx/Tx isolation of more than 50 dB. The proposed design has the merits of low profile, wideband, high isolation, and simple feeding structure, which makes it a competitive candidate for in-band full-duplex applications.

Melt pond detection on landfast sea ice using dual co-polarized Ku-band backscatter

The onset of melt ponds on landfast first-year and multiyear sea ice is detected using dual co-polarized Ku-band spaceborne scatterometer data. Twenty-nine locations in the Canadian Arctic Archipelago are used to develop and test the methodology. The daily ScatSat-1 sigma-nought backscatter composite product with a spatial resolution of 2.216 km is used. Vertical (VV) and horizontal (HH) polarizations of these data are used to derive the co-polarized ratio (VV/HH). An increase in VV/HH is associated with an increase in melt pond fraction on the sea ice. This occurs because there is a larger increase in resonant Bragg scattering for VV than for HH when melt pond surfaces exhibit wind-generated capillary waves. VV backscatter magnitude is evaluated in time series using a peak-finding methodology to initiate detection of melt ponds with VV/HH. The peak-finding is based on geophysical controls on backscatter from snow-covered sea ice during the melt season. Daily time-series data from ScatSat-1 are used in conjunction with ERA-5 reanalysis data (2-m air temperature and wind) and a semi-empirical snowmelt model. Air temperature data are used to identify snow melt onset and to force the snowmelt model. Wind data are used to evaluate if the wind speed is sufficient for capillary wave formation. The NSCAT-4DS geophysical model function is used to model Ku-band backscatter from water, which is then used in a sea ice mixture model to simulate the VV/HH magnitude for a range of pond fractions and wind speeds. The potential for detecting pond onset is evaluated in relation to the noise inherent in the ScatSat-1 VV/HH sea ice measurements, which is found to be approximately 0.16 dB. When the melt pond fraction is sufficiently large to cause VV/HH to exceed the noise, pond onset is detected. Cloud-free Sentinel-2 optical satellite imagery is used for validation; specifically, the near-infrared albedo. We find an overall mean bias of −0.5 days, and an absolute deviation of 1.4 days, when comparing our method to a near-infrared method for detecting pond onset. The mean biases (absolute deviations) for first-year and multiyear sea ice are −0.3 (1.5) and −0.8 (1.2) days, respectively. Results show that the temporal resolution, spatial resolution, and efficacy of this method can provide robust sea ice melt pond onset timing for landfast sea ice regions of the Arctic.

Analysis of multi-center topological domain states in BiFeO3 nanodot arrays

High-density ferroelectric BiFeO3 (BFO) nanodot arrays were developed through template-assisted tailoring of epitaxial thin films. By combining piezoresponse force microscopy (PFM) and Kelvin probe force microscopy (KPFM) imaging techniques, we found that oxygen vacancies in nanodot arrays can be transported in the presence of an electric field. Besides triple-center domains, quadruple-center domains with different vertical polarizations were also identified. This was confirmed by combining the measurements of the domain switching and polarization vector distribution. The competition between the accumulation of mobile charges, such as oxygen vacancies, on the interface and the geometric constraints of nanodots led to the formation of these topological domain states. These abnormal multi-center topological defect states pave the way for improving the storage density of ferroelectric memory devices.

Unwanted Supplementary Vibrations of Helicopter Radio Communication Systems

A helicopter in flight can be considered an unstable dynamic system with many unwanted vibrations originating from multiple sources, such as the operation of the engines and individual components. These vibrations cause the degradation of the structural and functional components of a helicopter, thereby generally reducing the utility and technical efficiency of the aircraft. During the analysis of frequently recurring errors of medium-heavy helicopters, partial damage to antenna elements with vertical polarisation was detected. These damages provided the basis for the presented research, based on which supplementary vibrations caused by unwanted electromagnetic oscillations were revealed. These oscillations were detected in the process of communication between the helicopter crew and the ground ATC (air traffic control) station. This phenomenon’s existence and negative influence were confirmed via measurements and modal analysis, based on which an exact synergy between harmonic frequencies of the helicopter’s normal vibrations was discovered. The obtained results serve as a theoretical and practical basis for the future monitoring of this phenomenon, especially in the process of determining the “health status” of medium-heavy helicopters.

A Pattern-Reconfigurable Endfire Antenna Based on Compact Folded Slot With Vertical Polarization

A pattern reconfigurable antenna with vertical polarization is proposed based on two folded near-coupled slot antennas. To achieve two end-fire beams and a bidirectional beam respectively, a central feeding structure and a reconfigurable feeding strip are designed based on the current reverse principle with the help of PIN diodes. A prototype has been fabricated and measured to validate this design. Three high-quality radiation beams have been obtained. In the two end-fire states, the measured peak gain can reach 7.15 dBi and the front-to-back (F/B) ratio is more than 22 dB at 5.7 GHz. In the bidirectional state, the measured peak gain can reach 3.94 dBi and the F/B ratio is less than 0.3 dB.

A wideband tri‐polarized water antenna

AbstractA wideband tri‐polarized water antenna is presented in this letter. Two orthogonal horizontal polarizations are realized by a water patch while one vertical polarization is realized by a water dielectric resonator antenna (DRA). To achieve wide impedance bandwidth and high isolation of the water patch, two pairs of L‐shaped probes with differential feeding technique are introduced. By adjusting the dimensions of the water patch and DRA properly, an overlapped bandwidth of 23.26% between three polarizations is achieved. Since the proposed antenna is mainly achieved by water of high optical transparency, it offers tremendous potential for future communication systems.

A Low-Profile Broadband Dual-Polarized Omnidirectional Antenna for LTE Applications

In this letter, a broadband dual-polarized antenna with a very low profile and omnidirectional gain patterns is designed for 1.7-2.7 GHz Long Term Evolution (LTE) mobile communications. The designed antenna is constituted by a miniaturized tapered monopole for vertical polarization (VP) and four planar dipoles arranged in a ring for horizontal polarization (HP). The HP antenna is used as the metal ground of the VP antenna, which can avoid the feeding intersection and solve the problem of impedance matching degradation when distance between the HP antenna and the metal ground of the VP antenna is close. By sharing the partial structure, the designed antenna achieves a compact size of 110 mm × 110 mm × 13 mm and an extremely low height of 0.07 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">min</sub> is the free-space wavelength at the minimum operating frequency). The design achieves an overlapping bandwidth of 45% (1.7-2.7 GHz) with an isolation higher than 20 dB. High efficiency, low cross polarization and good omnidirectivity in the horizontal plane are obtained. The designed antenna is fabricated and measured, and it performs a great consistency between the simulation and measurement.

Sentinel-1 time series data for sunflower (Helianthus annuus) phenology monitoring

The potential of time series of Sentinel-1 (S1) Synthetic Aperture Radar (SAR) data for monitoring crops and their phenological stages has long been recognized. However, sunflower (Helianthus annuus) is one of the crops whose interaction with microwave signal is still not fully understood. Here, we aim to analyze and interpret time series of S1 data for sunflower phenology monitoring. The SAR backscattering coefficients in VH (vertical-horizontal) and VV (vertical-vertical) polarizations as well as their ratio (VH/VV) in both ascending and descending orbits were retrieved for three sites located in three different agro-ecological regions in Ukraine. We observed that sunflower backscattering response differs for the ascending and descending orbits for the VV polarization and VH/VV polarization ratio due to the directional behavior of the flower head. Our analysis did not find major change in VH polarization for the two orbits. We also compared the S1-based sunflower phenology with that of Normalized Difference Vegetation Index (NDVI) derived from optical data acquired by Sentinel-2 (S2). Our analysis revealed a considerable correlation r2 > 0.4 between S1 and NDVI for VH and VV polarizations in both ascending and descending orbits; however, we observed lower correlation (r2 < 0.20) for the VH/VV polarization ratio in descending orbit (VH/VVdes). Based on the characteristics of sunflower phenology, we identified two sunflower phenological stages: beginning of flowering (BoF) and end of flowering (EoF). The difference between S1-based dates using VH/VVdes and reference dates was 4.1 and 4.4 days for the BoF and EoF stages, respectively; the use of VH/VVdes+asc yielded weaker results: 7.4 and 6.1 days. These results suggest that the VH/VVdes is a preferable parameter for identifying sunflower phenological stages such as BoF and EoF.

Surface Properties of Global Land Surface Microwave Emissivity Derived from FY-3D/MWRI Measurements

Land surface microwave emissivity is crucial to the accurate retrieval of surface and atmospheric parameters and the assimilation of microwave data into numerical models over land. The microwave radiation imager (MWRI) sensors aboard on Chinese FengYun-3 (FY-3) series satellites provide valuable measurements for the derivation of global microwave physical parameters. In this study, an approximated microwave radiation transfer equation was used to estimate land surface emissivity from MWRI by using brightness temperature observations along with corresponding land and atmospheric properties obtained from ERA-Interim reanalysis data. Surface microwave emissivity at the 10.65, 18.7, 23.8, 36.5, and 89 GHz vertical and horizontal polarizations was derived. Then, the global spatial distribution and spectrum characteristics of emissivity over different land cover types were investigated. The seasonal variations of emissivity for different surface properties were presented. Furthermore, the error source was also discussed in our emissivity derivation. The results showed that the estimated emissivity was able to capture the major large-scale features and contains a wealth of information regarding soil moisture and vegetation density. The emissivity increased with the increase in frequency. The smaller surface roughness and increased scattering effect may result in low emissivity. Desert regions showed high emissivity microwave polarization difference index (MPDI) values, which suggested the high contrast between vertical and horizontal microwave signals in this region. The emissivity of the deciduous needleleaf forest in summer was almost the greatest among different land cover types. There was a sharp decrease in the emissivity at 89 GHz in the winter, possibly due to the influence of deciduous leaves and snowfall. The land surface temperature, the radio-frequency interference, and the high-frequency channel under cloudy conditions may be the main error sources in this retrieval. This work showed the potential capabilities of providing continuous and comprehensive global surface microwave emissivity from FY-3 series satellites for a better understanding of its spatiotemporal variability and underlying processes.

Diversified path loss performance of dual-Polarised MIMO antenna in sub-6 GHz for RFID applications

ABSTRACT In this paper, the path loss performance of an eight-port Multiple-In-Multiple-Out (MIMO) antenna consisting of four circular slots radiator-based antenna elements is investigated in 3.5–3.75 GHz range for utilisation as an RFID tag and reader antenna. First, the S-parameters between the ports of two proposed MIMO antennas are measured in four channels of spatial diversity; one direct line-of-sight (LOS) and three indirect LOS in an anechoic chamber, each for the horizontal and vertical polarisation schemes at two distances, 5 and 25 cm, and the path losses between the ports of MIMO antennas are evaluated. Then, the path losses between the same MIMO antennas are obtained in a laboratory environment, which are higher by about 5–10 dB than those in the anechoic chamber and so, these losses are more dependent on the antenna position and nearby objects. The tag power sensitivity and the tag (read) range for the presented MIMO antenna are found to be more power level dependent than frequency dependent. The reported results confirm the performance of proposed MIMO antennas for RFID applications in addition to 5 G communications.

Reflector‐based highly isolated dual‐polarized multibeam antenna

AbstractIn this paper, a dual‐polarized multibeam antenna in X‐band is designed and physically fabricated using a parabolic reflector. The antenna consists of a feed array and a metal reflector. A dual‐polarized microstrip antenna array combining two design approaches, T‐coupled feed and defective ground structure, is adopted as the feed array to improve polarization isolation. In addition, the electromagnetic bandgap structure is loaded between the antenna units to reduce the mutual coupling and improve the isolation between the units. A nine element of the highly‐isolated dual‐polarized microstrip antenna array is designed to be placed on the focal plane of the parabolic reflector as the feed, and the beam deflection is realized by using the lateral defocus effect of the parabolic plane, which can finally realize nine single beams covering a 30° scanning range in both horizontal and vertical polarization modes. Based on the scanning state of multiple point beams, this paper uses the Fourier series for beam assignment to form a flat‐top beam with a wide scanning angle. The application of the antenna with two operating modes of wide beam and multibeam to navigational satellite systems can greatly improve the accuracy and efficiency of navigation.

A Quad-Band and Polarization-Insensitive Metamaterial Absorber with a Low Profile Based on Graphene-Assembled Film.

A quad-band metamaterial absorber using a periodically arranged surface structure placed on an ultra-thin substrate is demonstrated in this paper. Its surface structure consists of a rectangular patch and four L-shaped structures distributed symmetrically. The surface structure is able to have strong electromagnetic interactions with incident microwaves, thereby generating four absorption peaks at different frequencies. With the aid of the near-field distributions and impedance matching analysis of the four absorption peaks, the physical mechanism of the quad-band absorption is revealed. The usage of graphene-assembled film (GAF) provides further optimization to increase the four absorption peaks and promotes the low-profile characteristic. In addition, the proposed design has good tolerance to the incident angle in vertical polarization. The proposed absorber in this paper has the potential for filtering, detection, imaging, and other communication applications.

Metasurface-Covered Planar Endfire Antenna With Vertical Polarization

A trapped wave-based solution to design compact planar vertically-polarized (VP) endfire antennas is proposed in this paper. By placing a four-element series-fed magnetic dipole array with an inter spacing of half wavelength within a dual-layer metasurface and loading shorting pin arrays at two edges of the metasurface, the VP radiation is realized in a wide impedance band. In addition, the antenna profile can be further reduced by half according to the electric field distribution within the metasurface. Finally, a VP endfire antenna with a reflection bandwidth of 4.3 ~ 5.4 GHz, a peak gain of 9.8 dBi and a low total profile of 0.065λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the free-space wavelength at the center operation frequency) is designed for the validation. The proposed antenna can be used for some wireless communication systems on or near the ground plane, such as the car roof-mounted terminal for vehicle-to-roadside unit/base station communications.

Joint Design of Horizontal and Vertical Polarization Waveforms for Polarimetric Radar via SINR Maximization

For an extended target with different polarimetric response, one way of improving the detection performance is to exploit waveform diversity on the dimension of polarization. In this paper, we focus on joint design of transmit signal and receive filter for polarimetric radars with local waveform constraints. Considering the signal-to-interference-plus-noise ratio (SINR) as the figure of merit to optimize, where the average Target-Impulse-Response Matrix (TIRM) within a certain Target-Aspect-Angle (TAA) interval is employed as the target response, the waveform is decomposed and then designed for both horizontal and vertical polarization segments, subject to energy and similarity constraints. An iterative algorithm is proposed based on the majorization-minimization (MM) method to solve the formulated problem. The developed algorithm guarantees the convergence to a B-stationary point, where in each iteration, optimal horizontal and vertical transmit waveforms are respectively solved by using the feasible point pursuit and successive convex approximation (FPP-SCA) technique. Experiment results show the effectiveness of the proposed algorithm, the robustness of the output SINR against the TAA change, and the advantages of polarization diversity and local design.

A Compact Dual-Polarized Endfire Antenna Array for 5G Millimeter-Wave Terminal

This paper proposes a compact dual-polarized end-fire antenna array for 5G millimeter-wave (mmWave) application. The dual-polarized antenna unit is constructed by an open-ended substrate integrated waveguide (SIW) cavity for vertically polarized (VP) radiation and a broadband electric dipole for horizontally polarized (HP) radiation. By sharing the side walls of two neighboring SIW channels of the VP elements, the substrate integrated coaxial line (SICL) feeding structure for the HP element is achieved, thus a compact size of the final antenna array can be accomplished. To extend the bandwidth of the VP element, the quasi-TE <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> mode of the cavity and the slot mode of the end-fire aperture are adopted for the VP element. A corresponding linear array with four units is designed and fabricated. The common -10-dB impedance bandwidth covers from 24.8 GHz to 29.2 GHz. The maximum gain is 10.0 dBi for both polarizations, with an overlapped scanning coverage ranging from -41.5º to 45.5º at 27 GHz. The proposed design has a compact configuration, and a wide scanning range, which is alternative for 5G mmWave terminal application.

Code-Dependent Beam Shaping and Polarization Control by Binary Transmitarray

A code-dependent methodology is proposed to realize beam shaping and polarization control simultaneously by using binary transmitarray (BTA). The BTA unit elements are divided into two types which are linearly polarized in orthogonal directions. By individually designing binary code for each type of unit elements, the radiation pattern and polarization of the synthetic field can be simultaneously defined. To verify this mechanism, four BTAs are designed at Ka band with the same structures but with different binary codes to produce broadside directional beams with horizontal, vertical, left-handed circular, and right-handed circular polarizations, respectively. Furthermore, another BTA is designed to produce two directional beams pointing at different directions with left-handed and right-handed circular polarizations, respectively. Both simulations and measurements have verified that the proposed methodology provides a completely code-dependent mechanism to arbitrarily and independently design radiation patterns and polarizations of the BTAs. This methodology can be readily used to design binary programmable transmit arrays by integrating PIN or varactor diodes to the unit elements, so that radiation patterns and polarizations of the transmit arrays can be dynamically configured by merely changing the aperture codes, hence showing great values and potentials in communication and radar applications.

A high‐performance dual‐polarized corrugated horn for a compact antenna test range system

AbstractA high‐performance dual‐polarized horn antenna for a 5G millimeter wave compact antenna test range system (CATR) is proposed in this article. The feed antenna is mainly composed of a double‐ridged waveguide junction orthomode transducer (OMT), mode converter, and corrugated horn antenna. Among them, the OMT is the key device for the feed antenna to achieve dual polarization characteristics, and adopts a modular design method to apply the multi‐section impedance transformer in the vertical and horizontal polarization channels with good transmission characteristics. The corrugated horn antenna generates a symmetrical radiation pattern mainly in six corrugated slots. The proposed dual‐polarized corrugated horn antenna impedance matching bandwidth (VSWR &lt; 2) is 24–50 GHz. Moreover, the measured gain is 10–12 dBi, and the measured cross‐polarization level is less than −30 dB within the operating frequency range. Meanwhile, the half‐power beamwidth radiation pattern in the whole operating band has a good symmetry and the beamwidth in both E‐ and H‐plane remains stable. As a practical application, the designed antenna is used as the feed of the CATR system. The measured results show that the amplitude distribution in the quiet zone (QZ) is within ±1 dB, the phase distribution is within ±8°, and the cross‐polarization isolation is better than 27 dB. The performance of the QZ is conducive to the use of the CATR system.

Wideband Dual-Polarized Endfire Phased Array Antenna With Small Ground Clearance for 5G mmWave Mobile Terminals

A dual-polarized end-fire phased array antenna is presented for 5G mmWave mobile terminal applications. The antenna element combines a pair of top-hat dipoles with an open slot in two substrate layers. The dipole is excited by an open-ended substrate integrated waveguide (SIW) for vertical polarization, and the slot is coupled by a bent stripline for horizontal polarization. Both radiators can provide wide bandwidth, and share a small ground clearance of merely 1.6 mm. A 1 × 4 phased array is designed with an element spacing of 6 mm. Decoupling vias and decoupling slots are added between elements to improve port isolation. The simulated and measured overlapped bandwidth of the two polarizations are 21.4% and 14.6%, respectively. The isolation between any two ports is higher than 18 dB. The measured scanning beams of both polarizations are capable of covering ±42° within 3-dB gain variation.

Coupling analysis of polytetrafluoroethylene dielectric waveguides in the sub‐THz band

AbstractThis letter investigates the coupling between two parallel‐placed polytetrafluoroethylene (PTFE) dielectric waveguides over the frequency band from 90 to 110 GHz. The coupling is considered under different working frequencies, coupling spacings, coupling lengths, and polarizations. Simulations and measurements are carried out, and the results indicate the coupling can be significantly reduced by increasing the operating frequency and coupling spacing and adopting vertical polarization (VP) for a specific coupling length. In particular, the simulated and measured results with a 9‐mm coupling distance under two polarization states can be kept under −30 dB for 50‐ and 100‐mm coupling lengths, leading to negligible interference. In the practical arrangement of PTFE dielectric waveguides working at the other frequencies, one can follow the same rule to reduce the coupling between waveguides and thus avoid interference.