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A wideband, low profile transmitarray antenna (TA) operating in Ku-band (12GHz-18GHz) is proposed. The transmitarray antenna is composed of aperiodic transmitarray units arranged periodically. The TA unit is mainly composed of three layers, which are composed of metals and substrates. Square patches are printed on the substrate of the top and bottom layers, and the middle layer is a Jerusalem slot in the ground. The overall thickness of TA unit is 0.165λ0 (λ0 is the free space wavelength at 15GHz). In Ku-band, the insertion of the TA unit is less than 0.5dB, which reduces the backward radiation of the transmitarray antenna. The 360° phase is achieved by changing the length of the patch and slot, and the proposed transmitarray unit has a flat phase curve and great transmission characteristics. In order to verify the proposed design, a transmitarray antenna with 351 TA units operating at 15GHz is fabricated and measured. The measurement results show that the TA can achieve a 37.3% (14.4GHz-20GHz) 1-dB gain bandwidth, the measurement gain is 23.06dBi with 42.3% aperture efficiency at 15GHz, and the backward radiation level is below -15dB. The designed TA unit has symmetrical structure, so the transmitarray antenna can work in dual linear polarization or dual circular polarization.

A feeding network crossing method is proposed to form an N $\times $ N dual-polarized two-dimensional multibeam antenna array (2D-MBAA) with analog-digital hybrid beamforming, which solves the problem of needing additional connection structure between the dual-polarized antenna array and analog feeding network for large-scale antenna arrays. The main design work is focused on the analog-beamformer (ABF) and two structures are proposed. One is vertical-crossed (VC) ABF and the other is parallel-crossed (PC) ABF, and the latter is a more complex design in exchange for a significantly reduced profile. As a verification, a $4\times 4$ dual-polarized 2D-MBAA with PC-ABF has been fabricated and tested. It is operated at 3.45GHz with a bandwidth of about 10%, and it can realize a scanning angle of ±45°.

For the intelligence of metamaterials, the -sensing mechanism and programmable reaction units are two important components for self-recognition and -determination. However, their realization still face great challenges. Here, we propose a smart sensing metasurface to achieve self-defined functions in the framework of digital coding metamaterials. A sensing unit that can simultaneously process the sensing channel and realize phase-programmable capability is designed by integrating radio frequency (RF) power detector and PIN diodes. Four sensing units distributed on the metasurface aperture can detect the microwave incidences in the x- and y-polarizations, while the other elements can modulate the reflected phase patterns under the control of a field programmable gate array (FPGA). To validate the performance, three schemes containing six coding patterns are presented and simulated, after which two of them are measured, showing good agreements with designs. We envision that this work may motivate studies on smart metamaterials with high-level recognition and manipulation.

This communication proposes a dual-polarized end-fire phased array for 5G handset devices at 28 GHz. The proposed four-element array has low profile of 1.1 mm, small clearance of 2.7 mm, and symmetric patterns in the vertical plane. The array element is fed by substrate-integrated waveguide (SIW), which works as a waveguide (WG) antenna with vertically polarized radiation pattern. Two transition plates are introduced to improve the impedance matching of the WG antenna. The horizontal polarization is generated by exciting one of the transition plates as an antenna. The other transition plate is modified as a group of triangle strips to minimize its reflection to the horizontal radiation patterns. A -10 dB frequency bandwidth of 5.3% and a -6 dB bandwidth of 25% are achieved, overlapping between the vertical and horizontal polarization. The array scanning angle is from -54° to 44° at 29 GHz for both polarization. Within the scanning range, the end-fire gain varies from 7.48 to 8.14 dBi for the horizontal polarization, whereas from 4.49 to 8.05 dBi for the vertical polarization. Good agreements between simulations and measurements are well achieved and shown in this communication.

International audience; Spaceborne synthetic aperture radar (SAR) has been used for years to estimate high-resolution surface wind field from the ocean surface backscattered signal. Current SAR platforms have one single fixed antenna, and traditional inversion/retrieval schemes rely on one copolarized channel, leading to an unconstrained optimization problem for providing independent estimates of wind speed and direction. For routine application, this is generally solved with a priori information from the numerical weather prediction (NWP) model, inducing severe limitations for rapidly evolving meteorological systems where discrepancies can be significant between model and measurements. In this study, we investigate the benefit of having two simultaneous acquisitions with phase-preserving information in copolarization and cross polarization provided by Sentinel-1 (S-1). A comprehensive analysis of the co-cross-polarization coherence (CCPC) is performed to adequately estimate and calibrate CCPC values from S-1 interferometric wide (IW) mode images acquired over the ocean. A new polarimetric calibration (PolCAL) methodology based on least-squares (LS) criterion and direct matrix inversion is proposed yielding crosstalk estimates. We document CCPC odd symmetry with respect to relative wind direction for light to medium wind speeds (up to 14 m/s) and incidence angle from 30and#x00B0; to 45and#x00B0;. The azimuthal modulation is found to increase with both wind speed and incidence angle. An analytical model C-band polarimetric geophysical model function (CPGMF) is provided. The synergy of the CCPC with other radar parameters, such as backscattering coefficients or Doppler, to further constrain the inversion scheme is assessed, opening new perspectives for SAR-based wind field retrieval independent of any NWP model information. IEEE

A 3-D printed antenna subsystem, which proves its effectiveness in cost- & weight-reduction and reliability improvement over conventional CNC fabrication, is proposed in this paper. The proposed structure which integrates an orthogonal-mode transducer (OMT) and a corrugated horn is fully compatible to fabrication using high temperature resistant resin Acrylonitrile Butadiene Styrene (ABS) with 3-D printing technology, as well as coating using copper with electroless metallization method. Detailed design procedures are provided and a prototype operating at $X$ -band is designed, fabricated and measured. Over the whole operating frequency range of 11.7 GHz~12.7 GHz, measured reflection coefficients are better than −22 dB and −12 dB for different polarization directions. A very good isolation better than 60 dB is achieved between two input ports. The cross polarization level is at least 30 dB lower than the co-polarization. Moreover, the effectiveness of the fabricated antenna is also verified in a polarimetric radiometer system.

A dual-band dual-linear polarization reflectarray configuration is developed for future 5G cellular applications. A single layer unit cell including two pairs of miniaturized fractal patches is designed to operate at two distinct frequencies within the Ka-band (27/32 GHz), in a dual-polarization mode. An in-depth analysis of the unit cell behavior is carried out, to demonstrate the total independence between the designed frequency bands and polarizations. The proposed configuration offers a very simply and thin structure, small unit cell sizes, and low losses, while leading to an independent optimization of the phase at each frequency and polarization. A dual-band/dual-polarized reflectarray prototype is designed and tested, thus demonstrating the unit cell flexibility to offer arbitrary beam directions/shapes at each frequency, for both polarizations.

International audience; This paper presents two waveguide power dividers in a planar 4-way equiphasic dual-polarization power division configuration operating in the transmit Ku-band (10.7-12.75 GHz). Both concepts are primarily targeted as excitation networks for multiple accesses radiating elements or antenna arrays. The presented solutions are characterized by two different variants that accommodate for different manufacturing processes, namely subtractive manufacturing (SM) and additive manufacturing (AM). Their principal operations are described and finally their RF performance is presented and compared experimentally inter alia. The principal objective is to demonstrate the mechanical complexity of this type of microwave components and how 3D-printing enables its efficient realization via co-design.

International audience; This paper presents a new type of radiating horn-like radiating element which exploits a two- or four-port integrated overmoded power division depending on the aperture type and the requirement for single- or dual-polarization. The general concept is illustrated by two design examples which are proposed in this paper at Ku-Tx band (10.7 - 12.75 GHz); a single-polarized two-access rectangular aperture pyramidal horn and a dual-polarized four-access square aperture horn feed antenna. The generic operational principles call for a power divider which feeds two or four suitably flared waveguide sections which are further connected to a bi- or quad-furcated surface discontinuity for the combination of the incoming fields. Finally, a common waveguide region on top completes the total topology. This type of radiating elements exhibits a compact profile, while at the same time achieves high aperture efficiency (over 90%) due to robust materialization of the desired aperture modal content over a bandwidth of 20%.

This communication presents the experimental validation of independent and wide beam scanning with a dual-band transmitarray antenna (TA) in Satcom up- and down-links at Ka -band. The TA consists of two subarrays: one operates in the down-link with central frequency at 19.5 GHz, while the other one operates in the up-link centered at 29 GHz. Both subarrays share a common radiating aperture to obtain the compact configuration. The TA layout is made of 1 bit unit-cells and its design relies on the bifocal technique to extend the beam-scanning capability. The proposed bifocal prototype includes 1500 up-link unit-cells in a $30\times50$ matrix and 1581 down-link unit-cells arranged in a $31\times51$ rectangular lattice. The 1-D scanning is validated by displacing the feed horn along one direction. We show that the TA beam can be scanned in a ±40° and ±30° independently in each band while keeping a very low scan loss (

International audience; We present here the design and optimization of a dual-band dual linearly-polarized transmitarray antenna with a 1bit phase resolution (i.e. two phase states with 180° of relative phase-shift). The antenna operates in both downlink and uplink K/Ka-bands (17 - 21 GHz for the lower frequency band, and 27 - 31 GHz for the upper one) and could be used for satellite communication applications. In order to implement dual-band and dual-polarization, the unit-cell consists of four orthogonal superposed U-slotted patch antennas interconnected by a common metallized via hole. A 20×20 transmitarray based on the proposed unit-cell architecture has been optimized by using our in-house tool and validated through full-wave electromagnetic simulations. The 5×5 mm2 unit-cell size allows beam scanning over a large field of view (up to 80 deg.). A maximum gain of 23.4 and 21.4 dBi has been achieved at 29.1 GHz and 19.5 GHz, respectively. The 1-dB gain bandwidth is greater than 19.8% and 12% at the lower and the upper frequency bands, respectively. © 2021 EuMA.

This communication describes the performance of the dual-circularly polarized transmitarray antennas at the Ka -band with independent radiation characteristics. The proposed antenna architecture consists of a dual-linearly polarized (dual-LP) TA panel based on the interleaving technique combined with an add-on broadband polarizer to generate independent right-handed circular polarization (CP) (RHCP) and left-handed CP (LHCP) beams. This offers both dual-LP and dual-CP operation depending on the topology of the polarizer. The LP unit-cell is designed to achieve a 3 bit phase resolution, and the dual-LP TA panel is made of two interleaved single-LP subarrays with $52\times52$ and $53\times53$ elements operating in 45° and 135° single LP, respectively. The polarizer transforms the dual-LP into dual-CP while keeping the radiation independence of each polarization across the Ka -band. The experimental results obtained with three different prototypes pointing up to 50° validate the proposed concepts.

In this paper, a high-efficiency dual-polarized transmissive metasurface is presented for the generation of dual-mode convergent orbital angular momentum (OAM) beams. The proposed transmissive metasurface is composed of dual-polarized metasurface units, which are constructed from four stacked patches coupled through a Jerusalem-cross aperture on the interlayer ground, to complete the phase modulation for the orthogonal polarizations. The proposed transmissive metasurface units can achieve full 2π phase modulation along with low transmission loss. Converged OAM beams with modes numbers lx = +1 and ly = −2 are thus stimulated through the proposed transmissive metasurface for both orthogonal polarizations, which have been demonstrated numerically and experimentally.

In this paper, we describe the design of a dual polarized packaged patch antenna for 5G communications with improved isolation and bandwidth for K-band. We introduce a differential feeding technique and a heuristic-based design of a matching network applied to a single layer patch antenna with parasitic elements. This approach resulted in broader bandwidth, reduced layer count, improved isolation and radiation pattern stability. The results were validated through finite element method (FEM) and method of moments (MoM) simulations. A peak gain of 5 dBi, isolation above 40 dB and a radiation efficiency of 60% were obtained.

Since the polarization non-reciprocity errors are canceled out through optical compensation in dual-polarization interferometric fiber-optic gyroscopes (IFOGs), two ports, namely, the reciprocal and nonreciprocal ports, are both feasible sensing output. In this work, we propose and demonstrate a weighted subtraction method for noise suppression that utilizes the partial correlated two-port signals simultaneously. The relative intensity noise has reduced to 56.2% of its original value in the experiment and agrees with the theoretical analysis; as a result, the angle random walk is suppressed from ${\text{5.7}}\;\times\;{ \text{10}}^{-{\text{2}}}$ to ${\text{3.2}}\;\times\;{ \text{10}}^{-{{2\circ}}}/\sqrt{\mathrm{h}}$ with a 2-km-long fiber. The improvement on short- and long-term stability performance has been experimentally verified, which makes dual-polarization IFOG configuration promising for many applications.

In order to satisfy the communication requirements, a low profile + 45° / -45° dual-polarized base station antenna with a spacing of only 23 mm between the reflector and radiating surface is proposed. Different from the more common base station antenna units, the four folded dipoles are arranged in the same plane to form an octagon. When a single polarization is excited, the four folded dipoles are excited as a whole. Furthermore, two meandering L-shaped feeding lines are used to achieve a larger impedance bandwidth. Ultimately, this antenna has a relatively wide impedance bandwidth of 44.5% from 1710 to 2690 MHZ. The use of a reflector contributes to the formation of a stable radiation pattern, and aids in the realization of high cross polarization discrimination (XPD) available in the whole working frequency band. The antenna geometry description and operation principle are elaborated and several important parameters are also studied. The fabricated antenna array consists of 2 × 12 elements and the measurement results obtained demonstrate that the array meets the requirements in all bands of the DCS1800, PCS, 3G, and traditional WiMAX for modern communication on the eve of the 5G.

A new design of dual-polarization and multi-focus near-field focusing (NFF) reflective metasurface for wireless power transfer (WPT) system is proposed in this paper. In terms of multi-beam phase synthesis of reflective metasurface, the dual-polarization metasurface with independent regulation characteristics is introduced to realize multi-focus and high-efficiency WPT. The single-feed single-focus and the single-feed dual-focus metasurface working at X-band (10 GHz) with $26\times 26$ elements in two polarizations are designed, fabricated and measured by planar near-field scanning experiments. Furthermore, a compact antenna is designed and fabricated as the receiver to form a practical WPT system. The measurement results show that a NFF transfer system is 15 dB higher than a non-NFF transfer system. Through full-wave simulation and experiments of three cases, single focus, dual-focus, and single focus with dual-polarization can respectively realize the maximum focusing efficiency of 71.6%, 68.3% and 65.9%. The relative bandwidth with 50% power focusing efficiency of these three cases are all about 12%, which demonstrates the stability and feasibility of the NFF reflective metasurface for practical WPT applications.

The design of wide-passband dual-polarized elliptic frequency selective structures (FSSs) is proposed in this paper. The unit cell of the proposed structure is comprised of an array of cascaded square-patch resonators with a coupling layer consisting of two types of modified C-type and all-through slots. The designed FSS provides a third-order wide-passband elliptic filtering response, with three transmission poles in the passband and two transmission zeros at below and above the passband, respectively. The designed FSS is fabricated and its performance is measured. The measured results confirm that the proposed design achieves the desired wide-passband filtering performance with a fractional 3-dB bandwidth of up to 63% even for oblique incident angles up to 40°, for both TE- and TM- polarizations.

A beam-steerable dual-circularly polarized 60 GHz antenna array is proposed. A 1 &times, 4 dual-fed stacked patch antenna array is integrated with an 8 &times, 8 Butler matrix. By utilizing the 8 &times, 8 Butler matrix, the proposed antenna array generates dual-circular polarization with beam-steering capability. The proposed antenna array system demonstrates good reflection coefficients in the frequency band ranging from 55.3 GHz to 64.9 GHz and has a mutual coupling of less than &minus, 10 dB over the frequency range of 57.5 GHz&ndash, 63.2 GHz. At 60 GHz, the maximum gains and beam-steering angles for input ports 2, 4, 5, and 7 are 9.39 dBi at &minus, 38&deg, 10.67 dBi at &minus, 11&deg, 10.63 dBi at +11&deg, and 9.38 dBi at +39&deg, respectively. It is also demonstrated that the dual-polarization is well formed by switching the excitation ports. The right-handed circular polarization (RHCP) is formed when four ports from port 1 to port 4 are excited and left-handed circular polarization (LHCP) is formed when four ports from port 5 to port 8 are excited. The proposed antenna array system could be a good candidate for millimeter-wave 5G applications that require wide beam coverage and polarization diversity.

International audience; The design and optimization of a novel compact and highly efficient power divider exhibiting dual-polarization in an in-phase 2 \times 4 scheme (4-way) is presented. The two fundamental orthogonal modes TE -{10} and TE -{01} arrive in-phase on each of the four square waveguides for each polarization by the utilization of four 3-port turnstile junctions accompanied by four E-plane and two H-plane power division structures. The power divider ends up to two commercial waveguide (WR75) ports (each for one polarization). The presented passive component can be used as a dual-polarized feeding network for a 2 \times 2 antenna array or any four-port radiating element with square input waveguides and aperture sizes above 2.4 \lambda that are commonly targeted for focal array or direct radiating elements at GEO applications. The power divider is fully metallic, a fact that makes it an ideal candidate for satellite applications. The design band is Ku-Tx (10.7-12.75 GHz), presenting a Return Loss better than 20 dB and an input-output isolation of the orthogonal modes better than 30 dB. The exciter is also subjected to sensitivity analysis for estimating its manufacturing tolerances, exhibiting a robust behavior to dimensional variations, while its losses are also evaluated around 0.1 dB when aluminum parts are assumed. Finally, a compact topology of a 2.5 \lambda aperture size array in a 2 \times 2 scheme was designed and optimized where the level of aperture efficiency was the principal design goal. The array is after connected to the exciter to obtain the final feed system. © 2020 EurAAP.

Fifth generation (5G) mobile networks utilize millimeter-waves (mm-waves) to achieve higher data rates. This paper presents a dual-polarized antenna array that operates at 28GHz (27.5-29.5GHz) and 38GHz (37-39GHz) bands and is usable in mobile handsets. The array is based on slot antennas with separate feeds for each polarization and band. The multi-feed structure allows us to improve isolation between bands. The dual-polarized array has a peak realized gain of 10-13dBi and it is capable of beam-steering for up to ± 35° or ± 50° at 28GHz and 38GHz bands, respectively. The performance of the array in the presence of a smartphone chassis is also studied.

Sea ice drift detection has the key role of global climate analysis and waterway planning. The ability to detect sea ice drift in real-time also contributes to the safe navigation of ships and the prevention of offshore oil platform accidents. In this paper, an Enhanced Delaunay Triangulation (EDT) algorithm for sea ice tracking was proposed for dual-polarization sequential Synthetic Aperture Radar (SAR) images, which was implemented by combining feature tracking with pattern matching based on integrating HH and HV polarization feature information. A sea ice retrieval algorithm for feature detection, matching, fusion, and outlier detection was specifically developed to increase the system’s accuracy and robustness. In comparison with several state-of-the-art sea ice drift retrieval algorithms, including Speeded Up Robust Features (SURF) and the Oriented FAST and Rotated BRIEF (ORB) method, the results of the experiment provided compelling evidence that our algorithm had a higher accuracy than the SURF and ORB method. Furthermore, the results of our method were compared with the drift vector and direction of buoys data. The drift direction is consistent with buoys, and the velocity deviation was about 10 m. It was proved that this method can be applied effectively to the retrieval of sea ice drift.

There is an increasing demand for large format detector arrays with large bandwidths and high antenna efficiencies for future THz astronomical radiometric applications. For direct detection instruments, it is also desired to have antennas with dual polarization reception in order to increase the received power from incoherent sources, thereby improving the observing speed of the instrument. The main goal of this work is the validation of the incoherent detection of two orthogonal polarizations by a leaky lens antenna, coupled to a single Microwave Kinetic Inductance Detector (MKID). Depending on the absorbed power over a distributed transmission line, the resonant frequency of the MKID changes. The proposed antenna is composed of two crossed leaky wave slots feeding a silicon extended hemispherical lens. The slots are coupled to four aluminum (Al) coplanar waveguide (CPW) lines that incoherently absorb the incoming THz radiation. The antenna and the power absorbing CPW lines are embedded inside the MKID, allowing an efficient radiation detection at THz frequencies where no lossless superconductors are available. The proposed dual-polarized device absorbs power incrementally over four different CPWs incoherently and is therefore simulated in reception (deriving a plane-wave response) similarly to what is done in distributed absorbers. We compare numerically and experimentally the proposed dual-polarized leaky lens coupled MKID and its single polarization counterpart and show that the dual polarized device receives twice as much power as the single-polarized one. Eventually, the dual-polarized device, when used with air-bridges, provides the same angular selectivity and twice the throughput of the single-polarized one.

In this paper, a compact substrate-integrated waveguide (SIW) cavity-backed slot antenna array with high gain, broadband, and dual-polarization performances is proposed for 60-GHz applications. An enhanced 17.1% impedance bandwidth was achieved by cutting semi-circle edges on the conventional slot radiator. A simplified SIW feed network is aperture-coupled vertically and constructed on a double-layered structure to implement the dual-polarization operation. By adopting innovative techniques on both radiating element and double-layered SIW feed networks, a high-gain, broadband, and dual-polarized $8\times8$ antenna array was designed on three-layered printed circuit board that allows for mass production. This configuration also resolves the trade-off between the bandwidth and gain of the existing 60-GHz dual-polarized antenna array. Its feasibility is proved by obtaining a measured gain in the range of 19.7–22.3 dB and an enhanced impedance bandwidth of 17.1% over 55.7–66.1 GHz for both horizontal and vertical polarizations. With advantages of high-gain, broadband, and dual-polarization performances in a low-cost low-profile structure, the proposed antenna array is a promising candidate for millimeter-wave wireless systems.

An electromagnetic illusion method with planar metasurfaces is demonstrated numerically and experimentally. In the method, the scattering field of an arbitrary object can be built by using a planar ultrathin metasurface with dual-polarized subwavelength unit cells. The proposed planar illusion metasurface can disguise itself as an arbitrary object when the incident wave comes from a relative wide angle range, which means the proposed method is of great practical value.

This paper introduces concept, simulation and measurement results for a broadband dual-polarized stacked microstrip antenna with pin- and edge-feed for 5G applications in Ka-band. The design approaches take several requirements into account that are decisively for next generation 5G base stations. Dual-polarization for doubling link capacity, a large bandwidth for high data throughput as well as array compatibility are main issues. Especially the combination of these requirements makes the antenna design fastidiously. Techniques for bandwidth enhancement and dual-polarized feeding are elucidated. The realization is carried out in standard multilayer printed circuit board technology. The proof-of-concept shows that both antenna types reach measured -10 dB relative bandwidths between 12.8% and 16.4% with measured gains in mainbeam direction between 6.3 dBi and 7.1 dBi at 28 GHz.

International audience; Dual-frequency fiber lasers (DFFL) are shown to provide high purity beat notes for microwave signal generation and distribution. We study the stabilization of the beat from DFB DFFLs by using optical frequency-shifted feedback loop containing an electro-optic modulator (EOM). As a proof-of-principle of the method efficiency, a stabilized beat note with a phase noise level of -104 dBc/Hz at 1 kHz from a 1 GHz carrier, and of -90 dBc/Hz at 1 kHz from a 10 GHz carrier, is demonstrated when the EOM is driven by a synthesizer. Furthermore, the scheme is extended to a self-referenced scheme: a hybrid opto-electronic oscillator is obtained when the delayed DFFL beat note itself drives the EOM. Low-frequency phase noise is reduced by about 20 dB. Applications are discussed.

A novel silicon beam splitter based on modal and symmetry engineering in slot waveguides is reported. We experimentally demonstrate insertion loss and imbalance below 1 dB over a broad bandwidth of 390 nm, for both TE and TM polarizations., 2019 IEEE 16th International Conference on Group IV Photonics (GFP), August 28-30, 2019, Singapore, Singapore

A transmission-line-based decoupling technique for dual-polarized multiple-input and multiple-output (MIMO) antenna arrays is presented and analyzed. The proposed scheme enables well-canceled coupling for the adjacent elements under co-polarization, without degrading the isolation of the cross-polarized ports. First, a decoupling network based on the presented method for a $2 \times 2$ MIMO array is provided, along with a comprehensive design procedure. Calculations and simulations are operated to verify decoupling performance. For further verification, a $2 \times 2$ dual-polarized patch array with the proposed decoupling method is developed. The decoupling network characterizes low profile, compact size, and low insertion loss, which is realized in a single layer. Measurements denote that the isolations between the co-polarized elements are improved from 16 to 20 dB to over 30 dB after decoupling at the center frequency of 2.45 GHz. Subsequently, based on the proposed $2 \times 2$ decoupling method, a decoupling network for large-scale dual-polarized MIMO arrays is presented. A design example of a $4 \times 4$ dual-polarized patch antenna array is established. Full-wave simulations indicate that the isolations are enhanced to better than 30 dB with a small insertion loss of less than 0.45 dB and can widely be used for phased array and massive MIMO array systems.

© 2013 IEEE. The electromagnetic fundamentals that govern the performance characteristics of dual-polarized tightly coupled cross-dipoles that are widely used in cellular base station applications are investigated. The mutual coupling effects and their impact on standard performance indices are stressed. A model is developed that considers this type of cross-dipole as an array. Links between the physical dimensions of the components of these model and key radiation characteristics, including directivity, half-power-beam width, and cross polarization discrimination levels, are established. The model guides the introduction and optimization of a simplified cross-dipole structure that exhibits excellent performance. A prototype was fabricated, assembled, and tested. The measured results are in good agreement with their simulated values, validating the model, and its governing principles.

Sentinel-1 synthetic aperture radar (SAR) is one of the most advanced open-access satellite systems available, benefitting from its capability for earth observation under all-weather conditions. In this study, more than 280 Sentinel-1 SAR images are used to derive significant wave heights (Hs) of the sea surface using a polarization-enhanced methodology. Two study areas are selected: one is located near Hawai&rsquo, i in a deep water region, and the other is in transitional water off the U.S. west coast, where the U.S. National Oceanic and Atmospheric Administration (NOAA) buoy data are available for validations. The enhanced Hs retrieval methodology utilizes dual-polarization SAR image data with strong non-Bragg radar backscattering, resulting in a better estimate of the cut-off wavelength than from those using single-polarization SAR data. The new method to derive Hs is applied to SAR images from 2017 taken from both deep water (near Hawai&rsquo, i) and coastal water locations (off the U.S. West coast). The assessments of the retrieved Hs from SAR images suggest that the dual-polarization methodology can reduce the estimated Hs RMSE by 24.6% as compared to a single-polarization approach. Long-term reliability of the SAR image-derived Hs products based on the new methodology is also consolidated by large amount of in-situ buoy observations for both the coastal and deep waters.

This research addresses the use of dual-polarimetric descriptors for automatic large-scale ship detection and characterization from synthetic aperture radar (SAR) data. Ship detection is usually performed independently on each polarization channel and the detection results are merged subsequently. In this study, we propose to make use of the complex coherence between the two polarization channels of Sentinel-1 and to perform vessel detection in this domain. Therefore, an automatic algorithm, based on the dual-polarization coherence, and applicable to entire large scale SAR scenes in a timely manner, is developed. Automatic identification system (AIS) data are used for an extensive and also large scale cross-comparison with the SAR-based detections. The comparative assessment allows us to evaluate the added-value of the dual-polarization complex coherence, with respect to SAR intensity images in ship detection, as well as the SAR detection performances depending on a vessel’s size. The proposed methodology is justified statistically and tested on Sentinel-1 data acquired over two different and contrasting, in terms of traffic conditions, areas: the English Channel the and Pacific coastline of Mexico. The results indicate a very high SAR detection rate, i.e., >80%, for vessels larger than 60 m and a decrease of detection rate up to 40 % for smaller size vessels. In addition, the analysis highlights many SAR detections without corresponding AIS positions, indicating the complementarity of SAR with respect to cooperative sources for detecting dark vessels.

International audience; This letter investigates the potential of additive manufacturing for the fabrication of complex antenna geometries with enhanced performance at K-band. Stereolithography is here used to three-dimensionally (3D) print a novel topology of dual-polarized leaky-wave antenna that allows for the control of its aperture illumination both in phase and magnitude. The antenna consists of a modulated triple-ridge square waveguide perforated on its top wall with crossed slots of different sizes. An orthomode-transducer is integrated within the structure for dual-mode operation. Monolithic implementation of this compound 3D structure is only possible thanks to additive manufacturing. In addition, low weight and compactness are attained compared to classical milling. The present proposal is validated through the manufacturing of a low-sidelobe-levels prototype suitable for intersatellite links. The corresponding measured results are in a very good agreement with full-wave predictions.

As a manifestation of low-altitude wind shear, a downburst is a localized, strong downdraft that can lead to disastrous wind on the ground surface. For effective pre-warning and forecasting of downbursts, it is particularly critical to understand relevant weather features that occur before and during a downburst process. It is important to identify the macroscopic features associated with the downburst weather process before considering fine-scale observations because this would greatly increase the accuracy and timeliness of forecasts. Therefore, we applied the wind-vector potential-temperature energy analysis (WPEA) method and CSU-CHILL X-band dual-polarization radar to explore the features of the downburst process. Here it was found that prior to the occurrence of the downburst of interest, the specific areas that should be monitored in future events could be determined by studying the atmospherically unstable areas using the WPEA method. Combining the WPEA method with dual-polarization radar observations, we can better distinguish the phase distribution of the hydrometeor in the process and greatly enhance the judgment of the possibility of the downburst. From exploration of the microphysical features of the downburst, we further found that &lsquo, Zdr (differential reflectivity) column&rsquo, can be regarded as an important early warning indicator of the location of the downburst. Finally, a schematic of the formation process of the downburst according to the analyses was produced.

Atmospheric effect represents one of the major error sources for interferometric synthetic aperture radar (InSAR), particularly for the repeat-pass InSAR data. In order to further improve the practicability of InSAR technology, it is essential to study how to estimate and eliminate the undesired impact of atmospheric effects. In this paper, we propose the multi-resolution weighted correlation analysis (MRWCA) method between the dual-polarization InSAR data to estimate and correct atmospheric effects for InSAR topographic mapping. The study is based on the a priori knowledge that atmospheric effects is independent of the polarization. To find the identical atmospheric phase (ATP) signals of interferograms in different polarizations, we need to remove the other same or similar phase components. Using two different topographic data, differential interferometry was firstly performed so that the obtained differential interferograms (D-Infs) have different topographic error phases. A polynomial fitting method is then used to remove the orbit error phases. Thus, the ATP signals are the only identical components in the final obtained D-Infs. By using a forward wavelet transform, we break down the obtained D-Infs into building blocks based on their frequency properties. We then applied weighted correlation analysis to estimate the wavelet coefficients attributed to the atmospheric effects. Thus, the ATP signals can be obtained by the refined wavelet coefficients during inverse wavelet transform (IWT). Lastly, we tested the proposed method by the L-band Advanced Land Observing Satellite (ALOS)-1 PALSAR dual-polarization SAR data pairs covering the San Francisco (USA) and Moron (Mongolia) regions. By using Ice, Cloud, and land Elevation Satellite (ICESat) data as the reference data, we evaluated the vertical accuracy of the InSAR digital elevation models (DEMs) with and without atmospheric effects correction, which shows that, for the San Francisco test site, the corrected interferogram could provide a DEM with a root-mean-square error (RMSE) of 7.79 m, which is an improvement of 40.5% with respect to the DEM without atmospheric effects correction. For the Moron test site, the corrected interferogram could provide a DEM with an RMSE of 10.74 m, which is an improvement of 30.2% with respect to the DEM without atmospheric effects correction.

An X-band dual-polarization radar (XPRAD) was deployed in Guangdong province as part of the Southern China Monsoon Rainfall Experiment (SCMREX) during the storm season in 2016. This paper presents a comprehensive assessment of XPRAD observations during SCMREX with emphasis on data processing and rainfall products. The differential phase-based attenuation correction and radar calibration using self-consistency of dual-polarization observables are presented. It is found that the standard deviation of the Z d r bias is less than 0.2 dB based on ‘light rain at low angle’ and ‘dry aggregate snow’ observations. Cross-comparison with two standard S-band China New Generation Weather Radars (CINRAD) shows that the bias of Z h has a mean value less than 1.5 dBZ and a standard deviation less than 0.5 dBZ. In addition, fifteen rainfall events that occurred during the intensive observing period (IOP) are analyzed to demonstrate the rainfall estimation performance of XPRAD. In particular, rainfall accumulations at 1-, 2- and 3-h scales derived using R( K d p ) and R( Z h , Z d r ) relations are evaluated using national level rain gauge data and CINRAD-based rainfall estimation. The results show that both R( K d p )- and R( Z h , Z d r )-based products agree well with the rain gauge observations and CINRAD estimation. The difference between R ( K d p ) and R ( Z h , Z d r ) is not significant, although R ( K d p ) shows slightly better performance than R ( Z h , Z d r ) .

This paper presents the design procedure, optimization strategy, theoretical analysis, and experimental results of a wideband dual-polarized base station antenna element with superior performance. The proposed antenna element consists of four electric folded dipoles arranged in an octagon shape that are excited simultaneously for each polarization. It provides ±45° slant-polarized radiation that meets all the requirements for base station antenna elements, including stable radiation patterns, low cross polarization level, high port-to-port isolation, and excellent matching across the wide band. The problem of beam squint for beam-tilted arrays is discussed and it is found that the geometry of this element serves to reduce beam squint. Experimental results show that this element has a wide bandwidth of 46.4% from 1.69 to 2.71 GHz with ≥15-dB return loss and 9.8 ± 0.9-dBi gain. Across this wide band, the variations of the half-power-beamwidths of the two polarizations are all within 66.5° ± 5.5°, the port-to-port isolation is >28 dB, the cross-polarization discrimination is >25 dB, and most importantly, the beam squint is

International audience; Experimental results of dual-band transmitarray antennas operating in linear polarization are reported in this paper. The transmitarrays operate in both down-link and up-link for K/Ka-band satellite applications using orthogonal polarizations in each frequency band. The dual-band capability is obtained by interleaving two arrays of single-band unit-cells based on narrow patches and metalized via. Different prototypes are fabricated and measured to validate the performance in each band. A good agreement between theory and measurement is observed. The measured gain reaches 28.4 and 27 dBi at 29.6 GHz and 20 GHz respectively. At up-link, the -3-dB bandwidth is more than 11% around 29 GHz.

The radio noise that comes from the Sun has been reported in literature as a reference signal to check the quality of dual-polarization weather radar receivers for the S-band and C-band. In most cases, the focus was on relative calibration: horizontal and vertical polarizations were evaluated versus the reference signal mainly in terms of standard deviation of the difference. This means that the investigated radar receivers were able to reproduce the slowly varying component of the microwave signal emitted by the Sun. A novel method, aimed at the absolute calibration of dual-polarization receivers, has recently been presented and applied for the C-band. This method requires the antenna beam axis to be pointed towards the center of the Sun for less than a minute. Standard deviations of the difference as low as 0.1 dB have been found for the Swiss radars. As far as the absolute calibration is concerned, the average differences were of the order of −0.6 dB (after noise subtraction). The method has been implemented on a mobile, X-band radar, and this paper presents the successful results that were obtained during the 2016 field campaign in Payerne (Switzerland). Despite a relatively poor Sun-to-Noise ratio, the “small” (~0.4 dB) amplitude of the slowly varying emission was captured and reproduced; the standard deviation of the difference between the radar and the reference was ~0.2 dB. The absolute calibration of the vertical and horizontal receivers was satisfactory. After the noise subtraction and atmospheric correction a, the mean difference was close to 0 dB.

International audience; This paper presents the detailed experimental characterization of X-band 400-element transmitarray antennas in dual linear polarization. The latter can radiate two different and independent beams in two distinct directions with orthogonal polarizations. Two prototypes are designed and fabricated at 10 GHz; one with two beams radiating at boresight, and one designed for two beams pointing in a different direction in each polarization. A 3-dB gain bandwidth of 20% is reached for both polarizations and maximum gain is over 25 dBi for broadside beam.

It is well known that multipath effect remains a dominant error source that affects the positioning accuracy of Global Navigation Satellite System (GNSS) receivers. Significant efforts have been made by researchers and receiver manufacturers to mitigate multipath error in the past decades. Recently, a multipath mitigation technique using dual-polarization antennas has become a research hotspot for it provides another degree of freedom to distinguish the line-of-sight (LOS) signal from the LOS and multipath composite signal without extensively increasing the complexity of the receiver. Numbers of multipath mitigation techniques using dual-polarization antennas have been proposed and all of them report performance improvement over the single-polarization methods. However, due to the unpredictability of multipath, multipath mitigation techniques based on dual-polarization are not always effective while few studies discuss the condition under which the multipath mitigation using a dual-polarization antenna can outperform that using a single-polarization antenna, which is a fundamental question for dual-polarization multipath mitigation (DPMM) and the design of multipath mitigation algorithms. In this paper we analyze the characteristics of the signal received by a dual-polarization antenna and use the maximum likelihood estimation (MLE) to assess the theoretical performance of DPMM in different received signal cases. Based on the assessment we answer this fundamental question and find the dual-polarization antenna’s capability in mitigating short delay multipath—the most challenging one among all types of multipath for the majority of the multipath mitigation techniques. Considering these effective conditions, we propose a dual-polarization sequential iterative maximum likelihood estimation (DP-SIMLE) algorithm for DPMM. The simulation results verify our theory and show superior performance of the proposed DP-SIMLE algorithm over the traditional one using only an RHCP antenna.

The modern era of polarimetric radar begins with radiowave propagation research starting in the early 1970s with applications to measurement and modeling of wave attenuation in rain and depolarization due to ice particles along satellite−earth links. While there is a rich history of radar in meteorology after World War II, the impetus provided by radiowave propagation requirements led to high-quality antennas and feeds. Our journey starts by describing the key institutions and personnel responsible for development of weather radar polarimetry. The early period was dominated by circularly polarized radars for propagation research and at S band (frequency near 3 GHz) for hail detection. By the mid to late 70s, a paradigm shift occurred which led to the dominance of linear polarizations with applications to slant path attenuation prediction as well as estimation of rain rates and inferences of precipitation physics. The period from the early 1980s to 1995 can be considered as the “golden” period of rapid research that brought in meteorologists, cloud physicists, and hydrologists. This article describes the evolution of this technology from the vantage point of the authors. Their personal reflections and “behind the scenes” descriptions offer a glimpse into the inner workings at several key institutions which cannot be found elsewhere.

This study examines a novel extraction method for SAR imagery data of widespread flooding, particularly in the Chao Phraya river basin of central Thailand, where flooding occurs almost every year. Because the 2011 flood was among the largest events and of a long duration, a large number of satellites observed it, and imagery data are available. At that time, RADARSAT-2 data were mainly used to extract the affected areas by the Thai government, whereas ThaiChote-1 imagery data were also used as optical supporting data. In this study, the same data were also employed in a somewhat different and more detailed manner. Multi-temporal dual-polarized RADARSAT-2 images were used to classify water areas using a clustering-based thresholding technique, neighboring valley-emphasis, to establish an automated extraction system. The novel technique has been proposed to improve classification speed and efficiency. This technique selects specific water references throughout the study area to estimate local threshold values and then averages them by an area weight to obtain the threshold value for the entire area. The extracted results were validated using high-resolution optical images from the GeoEye-1 and ThaiChote-1 satellites and water elevation data from gaging stations.

This paper presents the design and measurements of a wideband dual polarized leaky lens antenna suitable for tightly spaced focal plane arrays. The antenna is composed of two crossed leaky slots fed by two orthogonal microstrips to realize the dual-polarization operation. The crossed microstrips are fed differentially in order to couple the radiation into the slots. The slots are then coupled to a dielectric lens to achieve directive patterns suited for feeding large Focal distance to Diameter ratio reflectors. In this paper, the proposed leaky lens antenna is optimized to achieve high aperture efficiency with clean symmetric patterns in both polarizations exceeding an octave bandwidth. The concept is validated by the measurements of the primary fields inside the lens and with GRASP simulations of the focal plane array.

International audience; Dual linearly polarized transmitarray antennas with wideband performance are investigated in X-band. Their designs are based on unit-cells with bandpass response. Their structures consist of three conducting layers printed on two identical dielectric substrates glued with a bonding film. Detailed experimental results demonstrate excellent polarization independence, with expected performance and properly preserved radiation characteristics for each polarization. The measured data are in excellent agreement with full-wave simulation results

Single and dual linearly-polarized receiving mode nanoantennas are designed for solar energy harvesting at 28.3 THz. The infrared rectennas are used to harvest the solar energy and converting it to electrical energy. The proposed infrared rectenna is a thin dipole made of gold and printed on a silicon dioxide substrate. Different shapes of the dipole arms have been investigated for maximum collected energy. The two poles of the dipole have been determined in a rectangular, circular and rhombus shapes. The rectenna dipole is used to concentrate the electromagnetic energy into a small localized area at the inner tips of the gap between the dipole arms. The dimensions of the different dipole shapes are optimized for maximum near electric field intensity at a frequency of 28.3 THz. A Metal Insulator Metal (MIM) diode is incorporated with the nanoantenna dipole to rectify the received energy. The receiving efficiency of the solar energy collector with integrated MIM diode has been investigated. A dual-polarized, four arms, rhombus shaped nanoantenna dipole for solar energy harvesting has been designed and optimized for 28.3 THz applications.

This paper introduces the design and analysis of circularly polarized (CP) and dual-polarized on-chip microstrip antennas for wireless communication at 60 GHz. The CP on-chip antenna consists of a circular aluminum patch with two overlapped circular slots fed by the transmission line. The radiation characteristics of the CP have been analyzed using the finite integration technique and finite element method based electromagnetic solvers. The CP antenna introduces left-hand circular polarization and employs as on-chip transmitter. A design of dual-polarized on-chip microstrip antenna at 60 GHz is investigated and is employed as on-chip receiver. The dual ports of the dual polarized antenna are designed with high isolation between them in order to be used as a two on-chip receivers. The radiation characteristics of the dual-port antenna have been calculated. The effect of the separation distance between the CP-antenna and the dual-polarized antenna on the same chip has been investigated. The performance parameters like the reflection coefficient, transmission coefficient, and the transmission gain of the two antennas at different separation distances have been introduced.

Differences in synthetic aperture radar (SAR)-retrieved hurricane wind speeds from co-polarization and cross-polarization measurements are found to be correlated with rain rate. A quality index is proposed for the SAR-retrieved wind speed product to recognize heavy rain- affected areas by taking account of the different imaging mechanisms of the radar backscattering from the ocean surface via cross-polarization and co-polarization observations. A procedure is proposed to rectify wind retrievals in the rain-contaminated areas within the hurricane core, based on the theoretical physical profile for hurricanes. The effectiveness of the proposed methodology for heavy rain area recognition and wind speed reconstruction in the rain-affected areas is validated against step frequency microwave radiometer measurements from hurricane reconnaissance missions and the hurricane surface wind analysis product (HWIND). The quality flags provide confidence levels of hurricane surface winds from SAR, which together with the proposed method to correct wind retrievals in rain-contaminated areas, can contribute to improved operational applications of SAR-derived winds under hurricane conditions.

In mountain basins, the use of long-range operational weather radars is often associated with poor quantitative precipitation estimation due to a number of challenges posed by the complexity of terrain. As a result, the applicability of radar-based precipitation estimates for hydrological studies is often limited over areas that are in close proximity to the radar. This study evaluates the advantages of using X-band polarimetric (XPOL) radar as a means to fill the coverage gaps and improve complex terrain precipitation estimation and associated hydrological applications based on a field experiment conducted in an area of Northeast Italian Alps characterized by large elevation differences. The corresponding rainfall estimates from two operational C-band weather radar observations are compared to the XPOL rainfall estimates for a near-range (10–35 km) mountainous basin (64 km2). In situ rainfall observations from a dense rain gauge network and two disdrometers (a 2D-video and a Parsivel) are used for ground validation of the radar-rainfall estimates. Ten storm events over a period of two years are used to explore the differences between the locally deployed XPOL vs. longer-range operational radar-rainfall error statistics. Hourly aggregate rainfall estimates by XPOL, corrected for rain-path attenuation and vertical reflectivity profile, exhibited correlations between 0.70 and 0.99 against reference rainfall data and 21% mean relative error for rainfall rates above 0.2 mm h−1. The corresponding metrics from the operational radar-network rainfall products gave a strong underestimation (50–70%) and lower correlations (0.48–0.81). For the two highest flow-peak events, a hydrological model (Kinematic Local Excess Model) was forced with the different radar-rainfall estimations and in situ rain gauge precipitation data at hourly resolution, exhibiting close agreement between the XPOL and gauge-based driven runoff simulations, while the simulations obtained by the operational radar rainfall products resulted in a greatly underestimated runoff response.

We propose new indicators for bivalve (oyster and mussel) beds on exposed intertidal flats, derived from dual-copolarization (HH + VV) TerraSAR-X, Radarsat-2, and ALOS-2 images of the German North Sea coast. Our analyses are based upon the Kennaugh element framework, and we show that different targets on exposed intertidal flats exhibit different radar backscattering characteristics, which manifest in different magnitudes of the Kennaugh elements. Namely, the inter-channel correlation’s real (K3) and imaginary (K7) part can be used to distinguish bivalve beds from surrounding sandy sediments, and together with the polarimetric coefficient (i.e., the normalized differential polarization ratio, K0/K4) they can be used as indicators for bivalve beds using multi-frequency dual-copolarization SAR data. Our results show that continuous bivalve bed monitoring is possible using dual-copolarimetric SAR acquisitions at all radar wavelengths.