Horizontal Polarization Research Articles

Endfire Circularly Polarized Planar Antennas: A review of their development

This article reviews and summarizes the developments of endfire circularly polarized (CP) planar antennas. The difficulty in designing such antennas is that there is not a large radiating aperture on a substrate to produce strong enough vertically polarized (VP) radiation to match the horizontally polarized (HP) radiation. Mainly based on the structures of radiation and feeding, endfire CP planar antennas are classified into several groups. The mechanisms of these antennas are identified, their performance is compared with tables, and the relation between performance and structures is explored. It is indicated that the distance between the phase centers of VP and HP radiators is a crucial parameter to affect the axial ratio (AR) bandwidth and beamwidth of an endfire CP antenna. It is addressed that it is essential to have strong VP radiation for a high-gain and wideband endfire CP antenna when substrates are thin.

The Polarimetric Radar Scattering Properties of Oriented Aggregates

Abstract The scattering properties of aggregates are studied herein. Early aggregates (<7 monomers) of branched planar crystals and mature aggregates (up to 100 monomers) of columns are randomly generated with varying assumptions about the monomer attachment processes and the orientation behavior during collection. The resulting physical properties of the aggregates correspond well with prior in situ and retrieved sizes and shapes. Assumed azimuthally uniform orientations during collection and monomer pivoting upon attachment resulted in flatter and denser aggregates. The column aggregates had lower density and more spherical shapes than the branched planar crystal aggregates. The scattering properties were calculated using the discrete dipole approximation for a set of orientation angles and transformed to spectral coefficients representing modes of orientation angle variability. The zeroth- and second-order coefficients dominate this variability, with the zeroth-order coefficients representing the scattering properties for randomly oriented particles. The second-order coefficients for backscatter showed differences between horizontal and vertical polarization increasing with density, and these coefficients for specific differential phase increase with both mass and density. Similarly, coefficients for the copolar covariance decreased with density. Rapid changes in the contributions to the radar moments from the second-order coefficients from low to moderate density were observed, likely due to the increasing presence of horizontally aligned monomers in the aggregate structure. Differences in how differential reflectivity and correlation coefficient evolve with the orientation distribution parameters suggest that these measurements, along with specific differential phase and reflectivity, provide complementary information about aggregate sizes, shapes, and orientation distributions.

Design of a Dual-Input Doherty Power Amplifier With Selectable Output Port

Power amplifiers (PAs) equipped with selectable or switchable output ports can often improve the performances of the microwave systems, especially in radar and satellite communication systems where both horizontal and vertical polarization can be utilized. To enable a selectable output port, this brief develops a dual-input dual-output (DIDO) Doherty power amplifier (DPA), which has a simple circuit topology. The DIDO-DPA is consists of two identical sub-amplifiers and a 90° coupler. The input amplitudes of the two sub-amplifiers and their phase difference is dynamically controlled leveraging on the dual-input technique, leading to a flexible power transferring and enhanced back-off efficiency. As a validation, a DIDO-DPA operating at 2.4 GHz is fabricated and measured in this brief. The fabricated DIDO-DPA delivers an output power of more than 43.3 dBm, a maximum drain efficiency (DE) of more than 69.5%, and a 6-dB back-off DE of more than 58% at each output port.

A ±45°-Polarized Antenna System With Four Isolated Channels for In-Band Full-Duplex (IBFD)

An in-band full-duplex (IBFD) antenna system having four ports with good self-interference cancellation (SIC) is presented in this article. Two of the four ports provide +45°-polarized radiation and the other two generate − 45°-polarized radiation. Every port of the proposed antenna is well isolated from the other three ports, enabling simultaneous transmitting (TX) and receiving (RX) with both two polarizations. To achieve this goal, three different types of couplings need to be addressed simultaneously. In this work, a novel isolation feed network is proposed, which is the first of its kind that can achieve three targets at the same time, i.e., feeding the antenna differentially, forming the original horizontal and vertical polarizations into ± 45° polarizations, and canceling out the reflected and coupled signals between the TX and RX ports. Then, a double-antenna IBFD system with four isolated channels is attained by combining the proposed feed network, defected ground structure (DGS), cross-shaped walls, and metal baffles, which effectively mitigated all the three types of couplings at the same time. The double-antenna system has high isolations of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt;$ </tex-math></inline-formula> 39 dB between any two of the four ports from 3.3 to 3.9 GHz. The four radiation patterns obtained by exciting the four ports are very similar to each other and are stable with frequency, which makes it an excellent candidate for 5G sub-6 GHz IBFD applications.

Design of Integrated Simultaneous Information and Power Receiver for WIPT Application

This letter presents the design and fabrication of a multifunctional simultaneous information and power receiver (SIPR) considering a multitone time-modulated array as wireless information and power transfer (WIPT). The proposed SIPR with Wilkinson power divider delivers power to information processing and DC generating blocks. The fabricated SIPR receives information in horizontal and vertical polarizations. A voltage-doubler-type rectifying circuit is designed for DC generation with a microstrip line model for the lumped parameter. DC generating block generates a maximum of 76% RF to DC power conversion. Furthermore, the bit error rate (BER) performance graph supports the use of the receiver for the digital modulation schemes.

A Single-Layer S/X- Band Shared Aperture Antenna with MIMO Characteristics at X-Band for Airborne Synthetic Aperture Radar Applications

New frequencies can be supported with very effective space use by using the shared aperture antenna This work presents on designing a dual-banddual-polarized (DBDP) S/X-band shared aperture antenna (SAA) for synthetic aperture radar (SAR) applications operating at S-band frequency (3.2 GHz) and X-band frequency (9.65 GHz). The single-layer SAA DBDP S-band antenna is designed in a square-shaped patch with coaxial feeding in both vertical and horizontal polarization. The X-band antenna design is in 1 × 3 vertical series with microstrip feeding and arranged at four corners of the proposed antenna. The S-band antenna is mainly used for airborne applications such as air traffic control and surface ship radar. In contrast, the X-band antenna application is maritime vessel traffic control, defense tracking, and vehicle speed detection for law enforcement. To verify the antenna, a prototype is fabricated and measured with s-parameters. The proposed design exhibits that the gain of the S-band is 7.2 dB and for the X-band is 12.4 dB, and the isolation is achieved more than −35 dB, and for this antenna, we achieved a bandwidth of 0.12 GHz for S-band and 0.27 GHz for X-band. However, the X-band antenna is a multi-input and multioutput antenna that is to be validated by using MIMO characteristic parameters such as envelope correlation coefficient (ECC), diversity gain (DG), channel capacity loss (CCL), mean effective gain, and mutual coupling. The MIMO characteristic parameter of X-band antenna values is found to be in a similar manner to both simulated and measured values. For this X-Band antenna, ECC, DG, CCL, and mutual coupling were achieved as below 0.05, 9.5 dB, 0.5 bps/Hz, and −30 dB to −55 dB, respectively. The total size of the antenna is 100 mm × 100 mm × 1.6 mm.

THz Pulse Generation and Detection in a Single Crystal Layout

The THz pulse of a few picosecond durations have been generated and detected via optical rectification and electro-optic effect within the same ZnTe crystal. An unbalanced single-shot detection scheme was performed to characterize the signal. As a result, a multicycle signal was obtained, in which two-photon absorption and other associated nonlinear effects were reportedly negligible. The experimental set-up is compact, economical, easy to build and has the added simplicity of facilitating an independent analysis of the horizontal or vertical polarization arm of the THz-modulated chirped probe beam. This work finds a useful application in integrated THz devices, narrow-band THz phonon spectroscopy and spectroscopic investigation of fast-occurring processes.

A Dual-Polarized Shared-Aperture Antenna With Conical Radiation Patterns and High Gain for 5G Millimeter-Wave Ceiling Communications

A dual-polarized (DP) antenna with a conical radiation pattern and high gain characteristics is proposed. It is mainly comprised of a horizontally polarized (HP) array, a vertically polarized (VP) element, a fence, and a feeding network. In the HP direction, a rotatable stacked substrate-integrated waveguide (SIW)-to-coaxial-to-SIW transition (SCST) is meticulously designed to yield omnidirectional radiation with low gain variations and low transmission loss. As for the VP direction, two orthogonal substrates that are arranged above the VP radiating element act as a holder to fix the director, resulting in gain enhancement. Here, the VP element is placed in the center of the HP array to share the aperture for size reduction. Moreover, the top-hat-shaped metal fence collaborates with the large-size ground plane to yield dual conical beams with high gain in DP directions. From the measured results, the HP direction has exhibited desirable bandwidth of 11.4% (24.8–27.8 GHz) with a peak gain of 11.6 dBi, and the VP direction has demonstrated wider bandwidth of 13.7% (24.5–28.1 GHz) with a corresponding gain up to 8.1 dBi. Notably, low gain variations of ±0.65 and ±0.8 dBi are also realized for the HP and VP directions, respectively. Therefore, a DP antenna with high-gain conical beams and low gain variations can be obtained for the fifth-generation (5G) millimeter-wave (MMW) ceiling communications.

Refreezing of Partially Melted Hydrometeors: Polarimetric Radar Observations and Microphysical Model Simulations

Abstract The discovery of a polarimetric radar signature indicative of hydrometeor refreezing has shown promise in its utility to identify periods of ice pellet production. Uniquely characterized well below the melting layer by locally enhanced values of differential reflectivity (ZDR) within a layer of decreasing radar reflectivity factor at horizontal polarization (ZH), the signature has been documented in cases where hydrometeors were completely melted prior to refreezing. However, polarimetric radar features associated with the refreezing of partially melted hydrometeors have not been examined as rigorously in either an observational or microphysical modeling framework. Here, polarimetric radar data—including vertically pointing Doppler spectral data from the Ka-band Scanning Polarimetric Radar (KASPR)—are analyzed for an ice pellets and rain mixture event where the ice pellets formed via the refreezing of partially melted hydrometeors. Observations show that no such distinct localized ZDR enhancement is present, and that values instead decrease directly beneath enhanced values associated with melting. A simplified, explicit bin microphysical model is then developed to simulate the refreezing of partially melted hydrometeors, and coupled to a polarimetric radar forward operator to examine the impacts of such refreezing on simulated radar variables. Simulated vertical profiles of polarimetric radar variables and Doppler spectra have similar features to observations, and confirm that a ZDR enhancement is not produced. This suggests the possibility of two distinct polarimetric features of hydrometeor refreezing: ones associated with refreezing of completely melted hydrometeors, and those associated with refreezing of partially melted hydrometeors. Significance Statement There exist two pathways for the formation of ice pellets: refreezing of fully melted hydrometeors, and refreezing of partially melted hydrometeors. A polarimetric radar signature indicative of fully melted hydrometeor refreezing has been extensively documented in the past, yet no study has documented the refreezing of partially melted hydrometeors. Here, observations and idealized modeling simulations are presented to show different polarimetric radar features associated with partially melted hydrometeor refreezing. The distinction in polarimetric features may be beneficial to identifying layers of supercooled liquid drops within transitional winter storms.

Wideband 3-D-Printed Metal-Only Reflectarray for Controlling Orthogonal Linear Polarizations

This article presents a metal-only reflectarray that enables the control of incident orthogonal polarizations in a large bandwidth. The proposed reflectarray is based on a unit cell whose tuning elements allow the independent control of the reflection phase value for the vertical and horizontal impinging polarizations. Due to the symmetry of the unit cell, the same performance is produced by each polarization when its reflection phase response is modified. The proposed unit cell provides a fairly linear phase response along the frequency with a phase variation in the orthogonal polarization of ±1°. The performance under oblique incidence and the frequency limitation of the unit cell are also investigated. From this unit cell, a metal-only reflectarray that produces circular polarization from a linear polarization is designed. The reflectarray presents a simulated directivity greater than 27 dBi with an axial ratio (AR) below 1.5 dB from 32 to 50 GHz (43.9% of bandwidth). A prototype is fabricated and the measured results agree well with the simulated ones. The obtained aperture efficiency is between 56% and 41% in the considered frequency band. The measured realized gain ranges from 27 to 30.3 dBi where the achieved radiation efficiency is greater than 97%.

Pixel Antenna Optimization Using the Adjoint Method and the Method of Moving Asymptote

The pixel concept offers a convenient and efficient method for antenna design. To meet the given specified antenna requirements or constraints, heuristic algorithms are often used to optimize the connection states for the hardwires between pixels, which are usually assumed to have the binary states, “short” or “open”. An alternative optimization strategy is proposed in this work, where the Boolean constraints on the hardwires are first relaxed to continuously tunable resistances and the globally convergent method of moving asymptotes (GCMMA) is applied to optimize the resistances. To speed up the computation, the adjoint method is used to simplify the calculation of the gradient information required in GCMMA. Resistances that are found as being above or below a certain threshold are then judged as “open” or “short”, respectively. Finally, the remaining intermediate resistance states are binarized using the successive exhaustive Boolean optimization (SEBO) method. Four different optimization strategies are proposed in terms of the objective function implemented in GCMMA and whether the second-stage SEBO is iterative or not. Two broadband endfire pixel antennas having horizontal linear polarization and high radiation efficiency are designed and fabricated correspondingly to demonstrate the feasibility of our proposed methods.

Classification of Arctic Sea Ice Type in CFOSAT Scatterometer Measurements Using a Random Forest Classifier

The Ku-band scatterometer called CSCAT onboard the Chinese–French Oceanography Satellite (CFOSAT) is the first spaceborne rotating fan-beam scatterometer (RFSCAT). A new algorithm for classification of Arctic sea ice types on CSCAT measurement data using a random forest classifier is presented. The random forest classifier is trained on the National Snow and Ice Data Center (NSIDC) weekly sea ice age and sea ice concentration product. Five feature parameters, including the mean value of horizontal and vertical polarization backscatter coefficient, the standard deviation of horizontal and vertical polarization backscatter coefficient and the copol ratio, are innovatively extracted from orbital measurement for the first time to distinguish water, first-year ice (FYI) and multi-year ice (MYI). The overall accuracy and kappa coefficient of sea ice type model are 93.35% and 88.53%, respectively, and the precisions of water, FYI, and MYI are 99.67%, 86.60%, and 79.74%, respectively. Multi-source datasets, including daily sea ice type from the EUMETSAT Ocean and Sea Ice Satellite Application Facility (OSI SAF), NSIDC weekly sea ice age, multi-year ice concentration (MYIC) provided by the University of Bremen, and SAR-based sea ice type released by Copernicus Marine Environment Monitoring Service (CMEMS) have been used for comparison and validation. It is shown that the most obvious difference in the distribution of sea ice types between the CSCAT results and OSI SAF sea ice type are mainly concentrated in the marginal zones of FYI and MYI. Furthermore, compared with OSI SAF sea ice type, the area of MYI derived from CSCAT is more homogeneous with less noise, especially in the case of younger multiyear ice. In the East Greenland region, CSCAT identifies more pixels as MYI with lower MYIC values, showing better accuracy in the identification of areas with obvious mobility of MYI. In conclusion, this research verifies the capability of CSCAT in monitoring Arctic sea ice classification, especially in the spatial homogeneity and detectable duration of sea ice classification. Given the high accuracy and processing speed, the random forest-based algorithm can offer good guidance for sea ice classification with FY-3E/RFSCAT, i.e., a dual-frequency (Ku and C band) scatterometer called WindRAD.

A compact dual-band dual-linearly polarized waveguide slot array antenna with groove at waveguide bottom

AbstractA dual-band dual-linearly polarized waveguide slot array antenna is proposed in this paper. Two orthogonal slots share a short-circuit wall on broad side. The horizontal and vertical slots, which actualize dual-frequency bands and dual-linear polarization, generate vertically polarized electric fields in 9.39–9.78 GHz and horizontally polarized electric fields in 11.62–12.3 GHz, respectively. The equivalent permittivity of the waveguide is changed by two grooves at the bottom of the waveguide, which improves phase velocity. Two grooves can also reduce the distance between the elements while suppressing the side lobes. Compared to filling the medium in the waveguide, two grooves have less losses. Moreover, the antenna is simple with one input port. The array antenna also overcomes the problems of beam scanning compared with the traditional waveguide slot array antenna. A 1 × 8 antenna array is fabricated and measured to verify the design. The horizontal polarization is formed in 9.39–9.78 GHz, the vertical polarization is generated in 11.62–12.3 GHz, and the antenna gain can reach 15 dBi.

Retrieving Soil Physical Properties by Assimilating SMAP Brightness Temperature Observations into the Community Land Model.

This paper coupled a unified passive and active microwave observation operator-namely, an enhanced, physically-based, discrete emission-scattering model-with the community land model (CLM) in a data assimilation (DA) system. By implementing the system default local ensemble transform Kalman filter (LETKF) algorithm, the Soil Moisture Active and Passive (SMAP) brightness temperature TBp (p = Horizontal or Vertical polarization) assimilations for only soil property retrieval and both soil properties and soil moisture estimates were investigated with the aid of in situ observations at the Maqu site. The results indicate improved estimates of soil properties of the topmost layer in comparison to measurements, as well as of the profile. Specifically, both assimilations of TBH lead to over a 48% reduction in root mean square errors (RMSEs) for the retrieved clay fraction from the background compared to the top layer measurements. Both assimilations of TBV reduce RMSEs by 36% for the sand fraction and by 28% for the clay fraction. However, the DA estimated soil moisture and land surface fluxes still exhibit discrepancies when compared to the measurements. The retrieved accurate soil properties alone are inadequate to improve those estimates. The discussed uncertainties (e.g., fixed PTF structures) in the CLM model structures should be mitigated.

Generation of Bessel beams with tunable longitudinal electric and magnetic fields using an all-dielectric metasurface.

Optical beams with a pure longitudinally polarized field are of great interest for their unique properties and promising applications in various fields such as optical trapping and three-dimensional microscopy. Here, an all-dielectric metasurface is proposed to directly generate Bessel beams with tunable longitudinally polarized electric and magnetic fields under a simple incidence of linear polarization. Under the incidence of horizontal polarization, a Bessel beam with a pure longitudinally polarized electric field can be generated, which can be turned to a beam with a pure longitudinally polarized magnetic field when the incidence is switched to vertical polarization. More importantly, it is further demonstrated that the longitudinal components of the electric and magnetic fields can be accurately manipulated between zero and the maximum by simply changing the polarization angle of incident light. The simplicity and flexibility of this proposed metasurface may provide new possibilities in ultracompact photonic devices for optical trapping, optical storage, and related fields.

Mapping the changes in the optical properties of azobenzene films due to photoisomerization

We used spectroscopic ellipsometry to study the dielectric function of an azobenzene polymer called Poly(disperse Red 1 methacrylate) (PDRM) as it underwent a photoisomerization process. The polymer films were fabricated by dissolving PDRM in tetrahydrofuran, and by spin coating films on silicon substrates. After fabricating the films, we used UV-VIS spectroscopic ellipsometry to determine the index of refraction, extinction coefficient and the thickness of each film. Using a heating cell coupled to the ellipsometer, we obtained temperature dependent ellipsometry data from 34 ℃ to 180 ℃, spanning a spectral region between 300 nm and 1500 nm. Using the raw data, we determined that the glass transition temperature of PDRM was 85 ℃ ± 3 ℃. Employing a three-oscillator model, we deduced the temperature dependent dielectric functions of PDRM films. Subsequently, the films were photoisomerized at two polarizations using a visible laser. For the horizontal polarization, there is nearly a 15% a change in the extinction coefficient as the PDRM films undergo a photoisomerization process.

A Microphysics-Scheme-Consistent Snow Optical Parameterization for the Community Radiative Transfer Model

Abstract The satellite observational data assimilation community requires consistent hydrometer descriptions—including mass–size relation and particle size distribution—to be used in both the forecast model and observation operator. We develop a microphysics-scheme-consistent snow and graupel single-scattering property database to meet this requirement. In this database, snowflakes are modeled as a mixture of small column and large aggregated ice particles, the mixing ratios of which may be adjusted to satisfy a given mass–size relation. Snow single-scattering properties are computed for four different mass–size relations. Subsequently, the snow description in the Thompson microphysics scheme is used as an example to demonstrate how microphysics-scheme-consistent snow bulk optical properties are derived. The Thompson-scheme-consistent snow bulk optical properties are added to the Community Radiative Transfer Model (CRTM), version 2.4.0. With CloudSat Cloud Profiling Radar (CPR) snow and liquid precipitation retrievals as the inputs, CRTM simulations are performed over global oceans and compared with four collocated Global Precipitation Measurement (GPM) Microwave Imager (GMI) high-frequency channel observations. The CRTM simulated brightness temperatures show agreement with the GMI observed brightness temperatures in cases of light-to-moderate precipitation over extratropical and polar ice-free oceans, with root-mean-square errors of 4.3, 13.0, 1.8, and 3.3 K in the 166-GHz (vertical polarization), 166-GHz (horizontal polarization), 183 ± 3-GHz (vertical polarization), and 183 ± 7-GHz (vertical polarization) channels, respectively. The result demonstrates the potential of using the newly developed microphysics-scheme-consistent snow optical parameterization in data assimilation applications.

Polarization/Frequency Hybrid Reconfigurable Microstrip Antenna Utilizing Graphene-Based Tunable Resistor

In this letter, a frequency and polarization hybrid reconfigurable microstrip antenna utilizing graphene-based tunable resistors is proposed. The antenna consists of a T-shaped power divider, a 90° phase shifter and a circular patch. Two pairs of graphene nanoplates connected with open-circuit lines are loaded on the left and right feeding lines of the power divider. By applying bias voltage from 0 to 4 V, the resistance of the graphene nanoplates can be dynamically tuned from 200 Ω to 20 Ω, thus the current flows through the graphene nanoplate to the open-circuit load, making the port inoperative. By choosing different single- or dual-port operation, the antenna can realize horizontal polarization or vertical polarization in the frequency bands 10.84–11.02 GHz and 11.79–12.1 GHz bands, respectively, and right-handed circular polarization in two bands. In addition, the gain manipulation function is completed by adjusting the resistance of the graphene nanoplates.

Autoencoder-extended Conditional Invertible Neural Networks for Unfolding Signal Traces

The reconstruction of cosmic ray-induced air showers from measurements of radio waves constitutes a major challenge. In this work, we focus on recovering the full three-dimensional electromagnetic field from two recorded signal traces of an antenna station covering two horizontal polarization directions. The simulated field is folded by a direction and frequency-dependent characteristic antenna response pattern, resulting in voltage signal traces as a function of time. Both signal traces are contaminated by simulated background noise. We use conditional Invertible Neural Networks (cINNs) to learn posterior distributions, from which the most likely electromagnetic field given a measured signal trace can be inferred. To improve robustness, we extend the method with an autoencoder by reducing the parameter phase space and decoupling the cINN from specific data shapes. Thereby, each signal trace is condensed into a small number of abstract parameters in the latent space on which the cINN operates. The presented method shows promising results and can be transferred to other unfolding problems where the recovery of the pre-measurement state is of interest.

A Coupled-Fed Broadband Dual-Polarized Magnetoelectric Dipole Antenna for WLAN and Sub-6 GHz 5G Communication Applications

This paper presents a novel coupled-fed broadband dual-polarized magnetoelectric dipole antenna for wireless local area network (WLAN) and 5G communication applications. The proposed magnetoelectric dipole antenna is composed of a planar electric dipole and shorting pins as a magnetic dipole to obtain a broad operation frequency band. Two coupled microstrip lines perpendicular to each other are coupled through a cross-shaped slot to excite the vertical and horizontal polarizations. The proposed antenna features a simple structure, high gain, and high polarization isolation. The measured impedance bandwidth of the proposed antenna is 1.8–4.2 GHz (fractional bandwidth of 80%). The measured realized antenna gain value is 3.7–8.5 dBi, and polarization isolation level is 25 dB at the operation frequency band.