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This article introduces a unique design approach for a compact in‐band full‐duplex (IBFD) antenna with good isolation in a wider bandwidth at the 2.4 GHz WLAN. The meander slot baluns are innovatively constructed in the feeding network, one balun on the top substrate layer and the other on the bottom substrate layer of the ground, to realize double differential feeding and polarization diversity. The metallic vias that connect one of the baluns in the feeding network with the co‐radiating patch further reduce the antenna's overall size. The balun's neutral coupling characteristics of differential potentials, which reduce the leakage currents by creating null potential, and differential filtering, which suppresses the leakage currents by non‐coupling fields, generate high isolation in the antenna. The designed balun offers a stable differential feed with a trivial magnitude and phase imbalances of (0.04–0.06) dB and ±10 $\pm {1}^{0}$, respectively. The antenna offers a minimum isolation of 78 dB with a wider bandwidth of 130 MHz. The far‐field measurement shows broadside radiation with low cross‐polar levels of less than −32 dB. A prototype is fabricated on FR‐4 substrate layers with an overall size of (0.8 × 0.8 × 0.012)λ0 ${\lambda }_{0}$ (λ0 ${\lambda }_{0}$ is the free space wavelength of the frequency f0=2.4 ${{f}}_{0}=2.4$ GHz) to validate the proposed design performance. The measured results of the prototype properly correlate with the simulated results. [ABSTRACT FROM AUTHOR]

Summary: This paper presents two different configurations of ±45° dual‐wideband dual‐polarized (DWDP) antennas. The antenna comprises eight end‐loaded broadband dipoles grouped into two sets based on the bands of operation. The high‐frequency dipoles are strategically placed within the low‐frequency ones to form the elementary unit. Further optimization has been performed on the elementary unit in terms of the radiator placement to suppress sidelobe levels for array formation. Both configurations are meticulously fabricated using an all‐metal structure, demonstrating durability and the simplicity of fabrication. The antenna designs achieve ±45° polarization, high gain, satisfactory cross‐polarization discrimination (XPD), and wide impedance bandwidth covering 0.67–1.04 GHz and 1.54–3 GHz bands. Despite the nested configuration, mutual coupling is well within acceptable limits. Formation of the array based on the optimum elementary unit has been investigated by simulation, revealing reasonable gain enhancement and low sidelobe levels across all bands. This comprehensive approach yields a robust, high‐performing antenna configuration suitable for indoor distributed antenna system (IDAS) applications. [ABSTRACT FROM AUTHOR]

Dual‐polarization programmable metasurfaces can flexibly manipulate electromagnetic (EM) waves while providing approximately twice the information capacity. Therefore, they hold significant applications in next‐generation communication systems. However, there are three challenges associated with the existing dual‐polarization programmable metasurfaces. This article aims to propose a novel design to address them. First, the design overcomes the challenge of element‐ and polarization‐independent controls, enabling more powerful manipulations of EM waves. Second, by using more energy‐efficient tunable components and reducing their number, the design can be nearly passive (maximum power consumption of 27.7 mW), leading to a significant decrease in the cost and power consumption of the system (at least two orders of magnitude lower than the power consumption of conventional programmable metasurfaces). Third, the design can operate in a broad bandwidth, which is attractive for practical engineering applications. Both the element and array of the metasurface are meticulously designed, and their performance has been carefully studied. The experiments demonstrate that 2D wide‐angle beam scanning can be realized. Moreover, secure communication based on directional information modulation can be implemented by exploiting the metasurface and an efficient discrete optimization algorithm, showing its programmable, multiplexing, broadband, green, and secure features. [ABSTRACT FROM AUTHOR]

In this article, we present and illustrate a flip-chipbased antenna-on-package (AoP) concept for the development of 5G mmWave massive MIMO antenna arrays and frontend modules. Unlike conventional Antenna-in-Package concepts, our concept provides the flexibility to choose suitable and separate layer stack-ups and packaging materials for enabling the antennas and the frontend components to meet their respective specifications. To illustrate this concept, we designed, fabricated, and measured novel dual-polarized broadband AoP arrays in the 39 GHz frequency band for 5G mmWave MIMO applications. The array consists of 16 identical stacked patch elements. Each single antenna possesses a driven patch, which is vertically stacked to a parasitic element to improve the antenna performance. It is excited by two orthogonal probe-feds for dual polarization. Furthermore, we designed and optimized antenna arrays together with the solder interconnects used for mounting the antennas onto the multilayered interposer. Our results show that these interconnects could cause up to about 0.5 dB reduction in the realized gain of the antenna array. The fabricated antenna arrays were measured from 33 to 41 GHz. A peak gain of approximately 16 dBi was measured. Excellent correlation was obtained between all the measurement and simulation results. [ABSTRACT FROM AUTHOR]

This study introduces a compact, wideband dual-polarized suspended patch antenna designed for LTE700/LTE850/CDMA850/GSM900 applications, with a focus on achieving high isolation. The antenna design has two suspended patches that are excited in orthogonal directions using a modified crossed-slot configuration. The modifications applied to the crossed-slot significantly enhance the -15 dB impedance bandwidth, resulting in improved port isolation between polarizations. Both theoretical analysis and experimental testing confirm these enhancements, revealing an impressive -15 dB impedance bandwidth of 37% (688-1000 MHz) and port isolation exceeding 35 dB in the operating band. The antenna exhibits symmetric and directional radiation patterns in principle planes, with half-power beamwidths ranging from 55.32° to 65.61° and 61.79° to 66.84°. Antenna gain show exhibits variation in the range of 7.3-8.4 dBi across the measured frequencies. The compact size of the antenna, measuring 380 × 380 × 43.6 mm², makes it highly suitable for integration into commercially deployed base stations. Throughout the paper, we provide a detailed presentation of the antenna's geometry, feeding mechanism, parametric studies, and experimental results. The combined theoretical analysis and practical experimentation validate the success of the proposed antenna design, highlighting its potential for robust performance in a wide range of communication applications. [ABSTRACT FROM AUTHOR]

Monitoring marine oil pollution holds both practical and scientific significance. Synthetic Aperture Radar (SAR) is an active microwave remote sensing technique capable of all-weather and all-day with fine spatial resolution. However, under low wind conditions, rain cells and young ice are examples of look-alikes affect the accuracy of oil spill detection. Polarimetric SAR assumes a crucial role in this context, as it can extract abundant polarimetric features by polarimetric target decomposition. Drawing inspiration from this advancement, an improved polarimetric feature named relative feature based on Cloude-Pottier target decomposition was proposed. The Jeffries-Matusita distance indicates the substantial potential of the relative feature in detecting oil spills. The improved polarimetric feature within U-Net, FCN-8s, and DeepLabv3+ResNet-18 for oil spill detection using polarization SAR images. Experiment results demonstrated that the relative feature has superior performance compared to other polarimetric features and obtained the highest accuracy and dice within U-Net compared to the other two models. These findings introduce promising concepts for achieving rapid and precise detection of oil spills in future applications. [ABSTRACT FROM AUTHOR]

A dual-polarized broadband coupled feed dipole antenna loaded with artificial magnetic conductor (AMC) structure is proposed. The proposed AMC structure with 4x4 elements shown in this paper consists of four perfect electrical conductor (PEC) rectangular strips and a ring to reduce the profile height of the dual-polarized dipole antenna. In addition, the dual-polarization antenna adopts coupling feed microstrip to excite two pairs of bow-tie patch. The overall size of the coupling feed dipole antenna is 1.1λ0x1.1λ0x0.09λ0 at 5.5 GHz. Measured results shows that the proposed dual-polarization antenna loaded AMC exhibit a 25.2% common working bandwidth (4.75-6.12 GHz). The isolation is less than -14 dB, and the peak gain is 10.6 dBi. This dipole antenna with AMC structure has the virtues of low profile, wide band, and good radiation performance and it has the potential to be used in C-band communication. [ABSTRACT FROM AUTHOR]

A dual-polarized broadband coupled feed dipole antenna loaded with artificial magnetic conductor (AMC) structure is proposed. The proposed AMC structure with 4x4 elements shown in this paper consists of four perfect electrical conductor (PEC) rectangular strips and a ring to reduce the profile height of the dual-polarized dipole antenna. In addition, the dual-polarization antenna adopts coupling feed microstrip to excite two pairs of bow-tie patch. The overall size of the coupling feed dipole antenna is 1.1λ0x1.1λ0x0.09λ0 at 5.5 GHz. Measured results shows that the proposed dual-polarization antenna loaded AMC exhibit a 25.2% common working bandwidth (4.75-6.12 GHz). The isolation is less than -14 dB, and the peak gain is 10.6 dBi. This dipole antenna with AMC structure has the virtues of low profile, wide band, and good radiation performance and it has the potential to be used in C-band communication. [ABSTRACT FROM AUTHOR]

A novel dual‐polarization (DP) rectangular horn with equal elliptical beams for synthetic aperture radar application is proposed. The DP elliptical beams with same beam width are achieved by loading groove with coupling gap in the rectangular horn narrow side. The key parameters of the proposed horn are analyzed and a prototype operated at S band is fabricated and measured. Good agreements between simulated and measured results are obtained. What's more, an elliptical reflector antenna based on the proposed horn feed array is devised. Compared with the common rectangular horn, the reflector with the proposed horn owns better DP radiation performance. [ABSTRACT FROM AUTHOR]

A strip‐typed patch antenna covered with a dielectric is studied. The antenna is excited with a differential feeding mechanism to obtain a low cross‐polarization level. When the patch antenna is totally covered with a dielectric, it can be operated at lower frequencies without tuning antenna dimensions. The simulated results show that as the relative permittivity of the dielectric is increased from 1 to 9.2, the antenna operation frequency is reduced from 4.25 to 2.38 GHz, and the cross‐polarization level is lower than −25 dB for each operation frequency. Based on such an antenna, a 1 × 8 dual‐polarized phased array is developed. The simulated results indicate that for each polarization mode, the gain variations of the array are less than 2 dB when the main beam is scanned from 60° to −60°; bedsides, a cross‐polarization level of less than −20 dB is also achieved. An array prototype is constructed, and measured data validate the simulated results. [ABSTRACT FROM AUTHOR]

In 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. [ABSTRACT FROM AUTHOR]

This paper proposes a low-profile highisolation dual-polarization array antenna operating in the L/S band. The radiating unit of the array antenna adopts U-shaped bending dipoles to realize the staggered arrangement of high- and low-band units, and is connected to the feeding network by a coaxial cable. To achieve the non-influence of high-band and low-band feed networks, multi-layer printing technology is used and grooves are etched on the metal plate. In order to reduce the coupling of the high- and low-band dipoles at low frequency, a bandpass filter is added to the highband feed network, which greatly improves the isolation at low-frequency. The measured results show that the impedance bandwidth of the array is 4.5% (0.971-1.015 GHz) and 7.5% (1.89-2.04 GHz), with gains of 15 and 19 dBi at 1 GHz and 2 GHz, respectively. And the isolation between the dual-polarized ports more than 50 dB and 35 dB was achieved at 1 GHz and 2 GHz, respectively. The proposed array will have practical value in L/S band full-duplex wireless communication systems. [ABSTRACT FROM AUTHOR]

Synthetic aperture radar (SAR) remote sensing technology has the advantage of all-weather observation and can acquire time-series images with crop growth period, which has great potential for applications such as crop phenology analysis. However, available studies primarily focus on conducting statistical and crop growth analyses based on the polarization or backscatter intensities of SAR images, and the exploration of polarization scattering information in SAR images is not sufficient. To comprehensively reflect the polarization characteristics and scattering mechanisms of crop at different growth stages, we propose a new method for extracting vegetation descriptors from Sentinel-1 dual-polarimetric SAR data. The method combines the backscattering intensity and polarization decomposition information to construct a normalized index q , which is used to generate three vegetation descriptors: the co-pol purity parameter (m cp ), the pseudo-scattering angle (θ cp ), and the pseudo-scattering entropy (H cp ). Further, a novel unsupervised clustering framework, founded on H cp and θ cp , has been proposed. This framework establishes six zones (named as Z1 to Z6) representing distinct physical scattering mechanisms, and by statistically sampling point data, it can determine the growth stage of the crops For validating the performance of the proposed vegetation descriptors and clustering framework, we conducted a three-year experiment using four crops from two publicly available datasets, namely wheat and canola from the Carman in Canada (Test site-1), corn and soybeans from Iowa in the United States (Test site-2). The experimental results indicate that m cp , θ cp , and H cp exhibit regular changes at different growth stages of crops from planting to maturity, with m cp and θ cp gradually decreasing while H cp gradually increasing. Within the entire phenology window, θ cp changes by approximately 42°, while both m cp and θ cp varies by about 0.9, and the sampling points shift from the Z2 to the Z5 zone. The vegetation descriptors are highly sensitive to the growth status of crops, and the clustering framework can also effectively respond to different growth stages of vegetation. Furthermore, the vegetation descriptors and clustering framework proposed in this study have the potential for extended application to different crop types and other polarimetric SAR data sources. [ABSTRACT FROM AUTHOR]

Based on the quality control of observational data, the heavy hailstorm that occurred in Yangjie Town, Weining County, Guizhou Province on June 28, 2018 is analyzed. The study combines a fuzzy logic hydrometeor identification algorithm with the mesoscale numerical model WRF and uses the X-band dualpolarization radar located in Xueshan Town, Weining County, Guizhou Province. The results show that there is a good consistency between the observation and model simulation results of this hail process, which mainly goes through four stages: development, ripeness (hail formation), ripeness (hail shooting) and attenuation (disappearance). (1) Development: Caused by the riming between ice crystals and surrounding super-cooled cloud water, low-density graupel (LDG) is formed near the cloud layer of -20 ℃ (5.0~6.8 km). Caused by the riming between aggregation (AG) and surrounding super-cooled cloud water, high-density graupel (HDG) is formed near the cloud layer with a terrain clearance of 2.6~4.2 km. (2) Ripeness (formation): AG is the main source of graupel embryo for LDG and HDG. The rain mixed with hail (RH) is initially formed near the cloud layer of - 20 ℃ (4.2~6.8 km) and it is caused by a small amount of HDG which collides with and freezes the super-cooled cloud water. (3) Ripeness (hail shooting): LDG is largely formed by coagulation. HDG develops from two sources: one is the riming with the AG particles (3.4 ~ 6.0 km) as the HDG embryo source, and the other is the gravity sedimentation by the top LDG particles (6.8 ~ 9.3 km), in which the particles develop into a large amount of HDG through coagulation with other ice phase particles during sedimentation. Finally, the HDG develops into the RH. (4) Attenuation (disappearance): HDG grows slowly by colliding with the super-cooled cloud water near the cloud layer of 0 ℃ (3.4 km). While falling continuously, LDG and HDG are gradually converted into liquid precipitation due to obvious melting effect. [ABSTRACT FROM AUTHOR]

A broadband dual‐polarized antenna array with excellent impedance matching and stable radiation performance is proposed. The array comprises four folded‐dipole antenna elements. Two trapezoidal baluns are used to excite the folded‐dipole antenna to obtain good impedance matching and generate a ±45°‐polarized radiation pattern. To improve the impedance matching and achieve steady radiation performance, a square parasitic director is used and placed above the folded dipoles. The antenna element realizes a broad bandwidth of 76.9% (voltage standing wave ratio [VSWR] < 1.5 from 1.69 to 3.8 GHz) and high isolation of 28 dB. Then an antenna array comprised of four elements is designed. It is fed by two miniaturized 1‐to‐4 power divides. Several metal baffles are added between adjacent elements to reduce the mutual coupling. The array achieves a broad bandwidth of 78.4% (VSWR < 1.5 from 1.66 to 3.8 GHz), high isolation of 25 dB, stable half power beamwidth in the E‐plane within 65° ± 5°, and high gain within 12–15 dBi. [ABSTRACT FROM AUTHOR]

In this work, a heterogeneous 6 × 4 dual‐polarized MIMO antenna array was developed to achieve antenna elements with uniform 10 dB‐beamwidth (120° ± 10°). To constrain the 10 dB‐beamwidth, two types of antenna elements are designed and properly placed in the antenna array according to the nonuniform electromagnetic coupling environment. A nonuniform aperiodic metasurface with equivalent capacitance loading effect is then proposed to compensate the inductance of the heterogeneous antenna array. It results in a low‐profile height of 0.17λL and good impedance matching over 40% bandwidth. The unit cells in the metasurface are arranged with non‐uniform spacing to achieve uniform 10 dB‐beamwidth of the antenna elements in an antenna array environment. Both simulation and measurement results validate that the proposed design achieves stable radiation patterns and uniform 10 dB‐beamwidth (120° ± 10°) over a wide frequency band of 1.8–2.7 GHz. Because of these attractive features, the proposed antenna array becomes a promising candidate for massive multiple‐input and multiple‐output base station antennas. [ABSTRACT FROM AUTHOR]

A miniaturized dual-polarized smartphone antenna based on tightly coupled dipole array (TCDA), applying to 5 G millimeter-wave (mmW), is presented. The antenna element has a size of 2.94 mm × 3.05 mm × 0.94 mm and covers a bandwidth of 91.5% and 88.4% with VSWR＜2 for pol-x and pol-y, respectively. To achieve low cost, compact size, and reduce the number of ports, a specific miniature feeding structure, using Γ-shaped coupling probes, is applied. The proposed smartphone antenna consists of eight elements with a size of 23.8 mm × 3.5 mm × 0.94 mm. Experiments show that the TCDA can support a minimum realized gain of 9.51 dB and 9.07 dB for pol-x and pol-y, respectively, within 5 G mmW bands. To verify the design concept, TCDA is fabricated and measured, which achieves 60° scanning without grating lobes. The measurement results demonstrate that the proposed antenna is well suited for future 5 G mmW mobile phones. [ABSTRACT FROM AUTHOR]

In this study, a dual-polarization and low-profile frequency-selective rasorber (FSR) constructed from a novel band-patterned octagonal ring and dipole slot-type elements is investigated. We show the process of designing from a full octagonal ring to realize a lossy frequency selective surface of our proposed FSR, and it has a passband with low insertion loss between the two absorptive bands. An equivalent circuit for our designed FSR is modeled to explain the introduction of the parallel resonance. Surface current, electric energy, and magnetic energy of the FSR are further investigated to illustrate the working mechanism. Simulated results indicate that S11 < −10 dB bandwidth within 5.2–14.8 GHz, S21 > −3 dB passband within 9.62–11.72 GHz, lower absorptive bandwidth within 5.02–8.80 GHz, and upper absorptive bandwidth within 12.94–14.89 GHz are obtained under normal incidence. Meanwhile, our proposed FSR possesses the properties of dual-polarization and angular stability. To verify the simulated results, a sample with thickness of 0.097 λL is manufactured, and the results are experimentally verified. [ABSTRACT FROM AUTHOR]

Urban impervious surface area is a key indicator for measuring the degree of urban development and the quality of an urban ecological environment. However, optical satellites struggle to effectively play a monitoring role in the tropical and subtropical regions, where there are many clouds and rain all year round. As an active microwave sensor, synthetic aperture radar (SAR) has a long wavelength and can penetrate clouds and fog to varying degrees, making it very suitable for monitoring the impervious surface in such areas. With the development of SAR remote sensing technology, a more advanced and more complex SAR imaging model, namely, polarimetric SAR, has been developed, which can provide more scattering information of ground objects and is conducive to improving the extraction accuracy of impervious surface. However, the current research on impervious surface extraction using SAR data mainly focuses on the use of SAR image intensity or amplitude information, and rarely on the use of phase and polarization information. To bridge this gap, based on Sentinel-1 dual-polarized data, we selected UNet, HRNet, and Deeplabv3+ as impervious surface extraction models; and we input the intensity, coherence, and polarization features of SAR images into the respective impervious surface extraction models to discuss their specific performances in urban impervious surface extraction. The experimental results show that among the intensity, coherence, and polarization features, intensity is the most useful feature in the extraction of urban impervious surface based on SAR images. We also analyzed the limitations of extracting an urban impervious surface based on SAR images, and give a simple and effective solution. This study can provide an effective solution for the spatial-temporal seamless monitoring of an impervious surface in cloudy and rainy areas. [ABSTRACT FROM AUTHOR]

A new scattering power decomposition method is developed for accurate tropical forest monitoring that utilizes data in dual-polarization mode instead of quad-polarization (POLSAR) data. This improves the forest classification accuracy and helps to realize rapid deforestation detection because dual-polarization data are more frequently acquired than POLSAR data. The proposed method involves constructing scattering power models for dual-polarization data considering the radar scattering scenario of tropical forests (i.e., ground scattering, volume scattering, and helix scattering). Then, a covariance matrix is created for dual-polarization data and is decomposed to obtain three scattering powers. We evaluated the proposed method by using simulated dual-polarization data for the Amazon, Southeast Asia, and Africa. The proposed method showed an excellent forest classification performance with both user's accuracy and producer's accuracy at >98% for window sizes greater than 7 × 14 pixels, regardless of the transmission polarization. It also showed a comparable deforestation detection performance to that obtained by POLSAR data analysis. Moreover, the proposed method showed better classification performance than vegetation indices and was found to be robust regardless of the transmission polarization. When applied to actual dual-polarization data from the Amazon, it provided accurate forest map and deforestation detection. The proposed method will serve tropical forest monitoring very effectively not only for future dual-polarization data but also for accumulated data that have not been fully utilized. [ABSTRACT FROM AUTHOR]

A wideband dual-polarized high-efficiency transmitarray antenna utilizing the isolated metal elements is proposed. First, a dual-polarized isolated metal element supported by a substrate frame is introduced. Each array element is isolated from adjacent elements by gaps. To realize the element, a substrate frame is used to completely fill the gaps and support the elements. As a result, the limitation of metal connections is overcome, and the transmitarray bandwidth is significantly enhanced. Based on equivalent circuit of the element, its wideband operating mechanism is revealed. Then, to reduce the manufacturing difficulties and costs while maintaining electrical performance, PCB technology is applied to the transmitarray fabrication, integrating the elements and the substrate frame. Finally, a wideband dual-polarized substrate-based metal transmitarray is designed, fabricated and measured. The measured results of the prototype indicate that its gain at the center frequency 10.2 GHz is 26.9 dBi, its 1-dB gain bandwidth is 23.4%, its efficiency is 56.1% and its lowest efficiency across the 1-dB gain bandwidth is 38% at 12.4 GHz. To the best of our knowledge, this is the first time a wideband two-layer substrate-based metal transmitarray has been proposed and implemented. [ABSTRACT FROM AUTHOR]

Simultaneously enhancing multiple antenna performance parameters is a demanding task, especially with a challenging set of design goals. In this paper, by carefully deriving a compatible set of enhancement techniques, we propose a compact/lightweight/low-cost high-performance L-band octagonal cavity-backed hybrid antenna with multiple attractive features: dual-polarization, wide impedance bandwidth, low cross-polarization, high gain, and high aperture efficiency. The ground cavity is octagonal, which allows the antenna to have a small footprint, and, more importantly, low cross-polarization and high aperture efficiencies when compared to a commonly-used square design. The hybrid design relies on the resonance merging of two radiating elements, i.e., radiating feedlines and a conductive open prism, to form a wide impedance bandwidth. To permit polarization diversity and low cross-polarization, it is differentially and orthogonally fed. Herein, a series of parametric simulation studies on antenna configurations provide information on how to improve the impedance bandwidth and cross-polarization performance. To verify the simulation studies, an antenna prototype was fabricated and tested. Excellent agreement between the simulated and measured results was reached. [ABSTRACT FROM AUTHOR]

This study proposes a new design approach for a dual‐band full‐duplex antenna to achieve high interport isolation using the differential fed technique. It consists of a single radiating patch, a differential fedline, and a direct fedline. A slotline‐based balun is used in the design to implement the differential fed, which offers minimum phase and magnitude imbalances to the patch of the antenna. The differential fed and direct‐fed lines are orthogonally connected to the radiating patch to realize dual polarization. Both the dual‐polarization and differential fed techniques help to improve the interport isolation of the antenna. It offers an interport isolation of more than 51 and 53 dB over the entire lower and higher operating bands, resonating at 3.22 and 4.1 GHz with 84 and 110 MHz bandwidths. To validate the proposed antenna, a prototype has been fabricated on an FR‐4 substrate with the dimensions of (1.79 × 1.79 × 0.017)λg (λg is the guided wavelength in the substrate at the lower frequency f1), with measured results consistent well with simulations. The far‐field measurement exhibits that the proposed antenna provides a unidirectional broadside radiation pattern and achieves a minimum cross‐polarization of less than −38 dB in all directions and less than −42 dB in the direction of the main lobe in both E‐ and H‐planes at the resonant frequencies. The antenna has insignificant backward radiation with the front‐to‐back ratio ≥ ${\boldsymbol{\ge }}$20 dB when port1 is active and the front‐to‐back ratio ≥ ${\boldsymbol{\ge }}$30 dB when port2 is active. Moreover, the proposed antenna design is simple and easy to fabricate as the differential fed is implemented using the slotline‐based balun within the same general purpose FR‐4 substrate layer. This eliminates the need for any additional and separate circuits for differential fed and minimizes the overall volume of the antenna. [ABSTRACT FROM AUTHOR]

In mirrored aperture synthesis (MAS), the antenna array determines the rank of the transformation matrix connecting the cross-correlations to the cosine visibilities. However, the transformation matrix is rank-deficient, resulting in errors in the reconstructed brightness temperature (BT) image. In this paper, the signal propagations for the vertically polarized wave and horizontally polarized wave are analyzed. Then, the optimization model of the antenna array based on dual-polarization is established. The optimal array configurations are presented, with the corresponding transformation matrices being almost column full ranks. Simulation results demonstrate the validity of the proposed optimization model. [ABSTRACT FROM AUTHOR]

A polarization‐insensitive frequency‐selective rasorber (FSR) with a high‐transmission passband and two wide absorption bands is proposed. The proposed FSR consists of an absorptive layer and a frequency selective surface (FSS) layer. The absorptive layer employs a four‐arm square spiral resonator with four fork shape resonators connected by lumped resistances to form broadband transmission and absorption. The FSS layer is formed by three metallic patches and two dielectric substrates, which are applied to generate a wide passband. The simulated results demonstrate that the 1‐dB transmission passband enables to obtain of 40.2% fractional bandwidth (FBW) from 9 GHz to 13.53 GHz, and the minimum in‐band insertion loss (IL) is 0.07 dB. Besides, the reflection bandwidth below −10 dB can reach 135% from 3.29 GHz to 16.90 GHz. Finally, the FSR's prototype is fabricated and measured. The results of measurement are fitted well with the simulated ones, which means that the proposed FSS can achieve broadband transmission and absorption. [ABSTRACT FROM AUTHOR]

A dual‐polarized wideband Fabry‐Perot (FP) antenna based on a wedge‐shaped phase correcting structure (WPCS) is proposed. The antenna adopts a wideband dual‐linear polarized slot‐coupled antenna as a primary antenna, and adopts a single‐layer FSS structure with positive reflection phase gradient characteristics as a partially reflecting surface (PRS) of the FP resonator, to optimally excite the FP cavity resonances within a wide operating band. Moreover, a small circular metal patch array is printed on the other side of the FSS unit structure. The small circular patch array effectively increases the reflection amplitude without changing the positive reflection phase gradient characteristics of the PRS, which improves the FP antenna gain. In addition, a highly graded WPCS is loaded in the resonant cavity to properly compensate the phase between different reflection paths inside the resonant cavity, which enhances the gain of the FP antenna in a wide band. Finally, the measured peak gains of the FP antenna under the excitation of Port 1 and Port 2 are 16.0 dBi and 15.89 dBi, respectively, and the gain enhancement can reach up to 3 dBi after loading the WPCS. The measured 10‐dB impedance‐matching operating bandwidth of dual‐polarized common coverage is 14.08 to 16.45 GHz (15.53%). [ABSTRACT FROM AUTHOR]

A novel bandwidth enhancement method using loading multiple parasitic structures to realize broadband miniaturized antenna is proposed. Based on the proposed strategies, one miniaturized wideband dual-polarized dipole antenna covering LTE/CDMA/GSM bands (690–960 MHz) for base-station application is designed. The antenna consists of two folded bowtie-shaped dipoles fed with a pair of crossed baluns, and is further loaded on a ceramic block with high permittivity ($\varepsilon$) for miniaturization. A parasitical square loop is loaded for bandwidth enhancement at a lower frequency. In addition, four split rings with a small square loop are firstly adopted for antenna resonance tuning, the impedance bandwidth is thus improved effectively. The antenna size is only $0.18\,\times \,0.18\,\times \, 0.22\,\,\lambda _{0}$ at the center frequency. The measured result of the fabricated prototype exhibits a relatively large operation bandwidth of 32.73% (VSWR < 1.6) with stable radiation patterns and relatively flat broadside gains. Moreover, to verify the feasibility of the proposed miniaturized antenna element in the base-station application, an array of $2\,\times \, 4$ is further designed. The measured results of the array indicate isolation over 20 dB with an impedance bandwidth of 32%. Due to the good performance and compact feature, the proposed miniaturized broadband antenna element can find large application potential in multiband wireless communication base stations. [ABSTRACT FROM AUTHOR]

A dual-polarized Ku-band and single-polarized Ka-band shared-aperture phased array antenna is proposed in this article. The endfire dipole antenna is designed as the radiating element of both bands. To eliminate the shading effect of the horizontal-polarized Ku-band antenna caused by the common ground, the director is loaded on the Ka-band antenna to increase the height of the equivalent phase center of the Ka-band antenna. The high-order mode of the horizontal-polarized Ku-band antenna is excited when the Ka-band antenna scans to a wide angle in H-plane within the frequency range of 33–34 GHz. An etched square ring is loaded on the Ku-band radiating arm to induce the reverse current to prevent such a high-order mode. The scanning blind spots occur at 33 and 35.8 GHz when the Ka-band antenna scans to 50° in E-plane owing to the mutual coupling between the Ka-band antenna and the vertical-polarized Ku-band antenna. A metallic strip is loaded on the vertical-polarized Ku-band antenna to eliminate the blind spot at 33 GHz. The feeding position of the vertical-polarized Ku-band antenna is elevated to eliminate the blind spot at 35.8 GHz. The periodic cell and finite array are simulated to verify the design proposed in this article. The results demonstrate that the design is effective and the beam-scanning coverage reaches $\pm \mathrm{50}^{\circ }$ at both bands. The active voltage standing wave ratio (VSWR) is not greater than 3.5 at 15–17 and 33–36 GHz in the whole beam-scanning coverage. A prototype of the 4 $\times $ 4 Ku-band and 8 $\times $ 8 Ka-band shared-aperture array is fabricated and measured. The measured results agree well with the simulated ones. [ABSTRACT FROM AUTHOR]

A wideband and wide beam‐width dual‐polarization with a low‐profile and simple structure is presented in this letter. The proposed antenna comprises two pairs of bending plates, the feed part that includes the probe and the copper disk, and two series of feeding networks. A couple of the bending plates can be used to form the horizontal and vertical currents to broaden the antenna's beam width. To radiate a symmetrical wide beam pattern, a series feeding network is applied to guarantee a symmetrical current distribution on the bending plates. Therefore, the proposed wide beam capability has been analyzed and verified with a dual‐polarization antenna. A low‐profile dual‐polarization antenna is demonstrated, which can realize the half‐power beam‐width more than 180° and 100° in the E‐ and H‐plane in the whole operating frequency band (22.3%), respectively. Furthermore, the port isolation is lower than −35 dB in the most frequency band. The prototype is fabricated and characterized, yielding good performance within the overall operational bandwidth. The measured results align very well with the simulated results. The proposed wideband antenna is a promising candidate for wireless communication systems because of the dual‐polarization and wide beam‐width. [ABSTRACT FROM AUTHOR]

Ship detection in synthetic aperture radar (SAR) images is a significant and challenging task. However, most existing deep learning-based SAR ship detection approaches are confined to single-polarization SAR images and fail to leverage dual-polarization characteristics, which increases the difficulty of further improving the detection performance. One problem that requires a solution is how to make full use of the dual-polarization characteristics and how to excavate polarization features using the ship detection network. To tackle the problem, we propose a group-wise feature enhancement-and-fusion network with dual-polarization feature enrichment (GWFEF-Net) for better dual-polarization SAR ship detection. GWFEF-Net offers four contributions: (1) dual-polarization feature enrichment (DFE) for enriching the feature library and suppressing clutter interferences to facilitate feature extraction; (2) group-wise feature enhancement (GFE) for enhancing each polarization semantic feature to highlight each polarization feature region; (3) group-wise feature fusion (GFF) for fusing multi-scale polarization features to realize polarization features' group-wise information interaction; (4) hybrid pooling channel attention (HPCA) for channel modeling to balance each polarization feature's contribution. We conduct sufficient ablation studies to verify the effectiveness of each contribution. Extensive experiments on the Sentinel-1 dual-polarization SAR ship dataset demonstrate the superior performance of GWFEF-Net, with 94.18% in average precision (AP), compared with the other ten competitive methods. Specifically, GWFEF-Net can yield a 2.51% AP improvement compared with the second-best method. [ABSTRACT FROM AUTHOR]

This article presents the design and analysis of a dual-polarized low-profile circuit analog absorber with wideband absorption characteristics. A lossy frequency selective surface consisting of cross dipole with central resonant node element is used as the top layer, while there is a continuous copper ground as the bottom layer. The novelty of the design lies in the use of the resonant node as it improves the absorption bandwidth by providing an additional resonance without compromising the low-profile nature of the design. It has a thickness of 0.077 $\lambda_{L}$ (where $\lambda {\_}L$ is the wavelength corresponding to the lowest operating frequency). The absorber also exhibits a stable absorption characteristics up to 30 $^\circ$ angle of incidence and can avoid grating lobes within the operating bandwidth up to 40.79 $^\circ$ angle of incidence. An equivalent circuit model is proposed to discuss the operating principles of the design. The validation of the design is done experimentally using the time-gating technique, and a good agreement between the measured and the simulated results is observed. The 10-dB reflection reduction bandwidth and the thickness-to-bandwidth ratio of the absorber are obtained as 108.67% (from 3.58 to 12.10 GHz) and 0.104 from full-wave simulation and 115.67% (from 3.5 to 13 GHz) and 0.098 from measurement, respectively. [ABSTRACT FROM AUTHOR]

In this paper, an orbital angular momentum (OAM) metasurface antenna is proposed. Based on the idea of controlling the radiation and scattering simultaneously, the metasurface unit cells play two roles of radiating and scattering energy. For radiation, the metasurface unit cells are excited by two carefully designed phase shift networks (PSNs) at two orthogonal directions. Thus, OAM vortex waves with topological charge l = ±1 are generated at 7.48 GHz band. For scattering, the incident wave is deflected through the phase canceling scheme due to the anisotropy property of the metasurface unit cells. As a result, the in‐band radar cross section is reduced. A prototype of the antenna was fabricated and measured. The measurement results agreed well with the simulations. [ABSTRACT FROM AUTHOR]

In this article, a differentially fed dual-polarized dielectric resonator antenna (DRA) subarray excited by a substrate integrated waveguide (SIW) cavity is proposed. A #-shaped slot etched on the top wall of the SIW cavity is used to achieve the differential excitation due to the intrinsic field distribution of TE120 mode in the SIW. Based on the proposed antenna subarray, a $2\times $ 2 dual-polarized 2-D multibeam DRA antenna array with simple structure is designed, fabricated, and measured, which can achieve high cross-polarization discrimination (XPD) in the direction of maximum radiation. To reduce substrate loss, the printed ridge gap waveguide (PRGW) technology is used to feed the SIW cavity. Two orthogonal PRGW Butler matrices are placed at different layers so as to realize 2-D beamforming scanning with dual-polarization. The SIW cavity is placed in the air gap of PRWG, which can increase the stability of the antenna structure. By cleverly combining the SIW cavity and PRGW structure, the proposed multibeam antenna array has the advantages of high XPD and high radiation efficiency. Measured results show that an impedance bandwidth of 10% (28.5–31.5 GHz) and a peak gain of 11.8 dBi are obtained. Also, the measured XPDs are 28.3 dB at the center frequency and larger than 19.2 dB over the band of operation. Besides, the measured radiation efficiency of 67% is achieved for both the polarizations at 30 GHz. [ABSTRACT FROM AUTHOR]

A high-efficiency wideband double-layer transmitarray antenna (TA) using miniaturized array elements is proposed in the study for millimeter-wave (mm-Wave) applications. The transmitarray consists of 484 dual-polarized elements. Each element is composed of only two layers of identical modified Jerusalem crosses printed on a dielectric substrate. Additional stubs are used for size reduction, leading to a compact size with a periodicity of only $0.44 \lambda _{0}$. It contributes to a high aperture efficiency for the proposed TA. TA is designed, fabricated, and measured. It achieves a peak gain of 28.67 dBi at 31 GHz and a high aperture efficiency of 44%–61.3% within the 1 dB gain bandwidth, which is 10.3% (29.5–32.7 GHz) in the measurement. The proposed dual-polarized double-layer TA demonstrates simplified design complexity, reduced thickness and mass, and lower cost compared with the conventional TAs. It also exhibits high radiation gain and high aperture efficiency. [ABSTRACT FROM AUTHOR]

The concept of dual-polarized reconfigurable reflectarray (RRA) featuring dual-polarized beam control is proposed and demonstrated using a dual-channel programmable metasurface. The p-i-n diodes are incorporated into each metasurface element as the active components to provide independent phase control in two orthogonal polarization channels. By altering the working states of each p-i-n diode, well-defined beam scanning can be obtained. Element design, focal diameter ratio selection, and discretized phase distributions are carefully optimized to ensure stable radiation performance of the proposed RRA. As verification, a prototype consisting of 20 $\times20$ elements is fabricated and measured, which is controlled by a field programmable gate array-based controller. Measured results show that wide-angle beam scanning up to ±40° can be obtained around 7.45 GHz, with peak gains of 21.13 and 20.89 dBi in dual channels, corresponding to aperture efficiencies of 16.35% and 15.47%. The proposed dual-polarized RRA brings a new freedom in polarization manipulations for versatile beam scanning, which provides promising applications in wireless communication and tracking/detecting systems. [ABSTRACT FROM AUTHOR]

This communication presents a novel bifunctional metasurface (MS) combining the reflectarray (RA) and transmitarray (TA) with dual-band orthogonally polarized dual-beam characteristics. The proposed reflect-transmit-array (RTA) is capable of reflecting the $x$ -polarized incidence without changing its polarization state around 10 GHz while transmitting the $y$ -polarized incidence and converting it into the circularly polarized (CP) waves around 14 GHz. To completely cover the working frequency bands of both modes, an antipodal Vivaldi antenna (AVA) is introduced as the source feed due to its intrinsic ultrawideband characteristics. As a proof of concept demonstration, a prototype consisting of 20 $\times20$ elements is also designed, fabricated, and measured. We observe a good agreement between the measurement and simulation results that shows a peak gain of 26.2 dBi and 27.3 dBic, 1 dB gain bandwidth (BW) of 9.8–11.3 GHz (14.2%) and 12.8–14.2 GHz (10.4%), and peak aperture efficiency (AE) of 48.7% and 35.1% for the reflection and transmission modes, respectively. [ABSTRACT FROM AUTHOR]

A dual‐polarized substrate‐integrated hollow antenna (SIHA) and its cylindrically conformal phased array are proposed. The bandwidth of the proposed SIHA is 35%. The cylindrically conformal phased array with 24 SIHA subarrays can scan its beam in the whole horizontal plane and scan its beam within ± 60° in the vertical plane. The proposed array with wide band, wide‐angle scanning, and dual‐polarization characteristics is appropriate for millimeter‐wave base station applications. [ABSTRACT FROM AUTHOR]

The enhanced nonreciprocity for transverse electric wave (TE) and dual-polarization light is investigated. The device is composed of a cascaded dielectric-Weyl semimetal film sandwiched between a high contrast grating and a dielectric substrate. The results indicate that near-complete nonreciprocity can be observed for TE wave for light under conical incidence, which is attributed to the guided mode resonance (GMR) excited by the high contrast grating demonstrating by analyzing the normalized electric field intensity distribution. Further, impedance matching condition has also been employed to confirm the underlying physical origin. In addition, the strong nonreciprocal radiation properties could be remained stably insides a broad geometrical parameter range. More importantly, the structure can be expanded to realize dual-polarization nonreciprocal radiation for both TE- and TM-polarized wave. The concepts and conclusions obtained here will be interesting for the developing of novel polarization-dependent and dual-polarization nonreciprocal radiation devices. [ABSTRACT FROM AUTHOR]

Base station antenna usually requires dual-polarization operation with satisfactory input return loss, adequate dual-polarization isolation, stable gain, and half-power beamwidth (HPBW) in a wide bandwidth covering the entire or part of the mobile communication bands. Such comprehensive requirements provoke great challenges in antenna design. A novel design scheme is proposed by involving fragment-type structures (FTSs) in antenna and seeking for the optimal FTS by multiobjective optimization searching. The technique is demonstrated by improving crossed dipoles for operation in band ranging from 1.7 to 3.8 GHz. Part of the dipole arms can be gridded into cells and reconfigured by using FTS elements. For automatic optimization searching, a binary coding scheme for both the FTS distributions and canonical dipole structure dimensions is proposed. Simulation and measurement show that the optimal crossed dipole antenna may acquire a wide operation bandwidth of 76.3%, with the return loss higher than 15 dB, isolation higher than 30 dB, HPBW of 65° ± 5°, and gain of 9 dBi ± 0.65 dBi for ±45° polarizations. [ABSTRACT FROM AUTHOR]

Polarization calibration without artificial calibrators has been one of the focuses of research and discussion for PolSAR communities. However, there is limited research on the treatment of dual-polarization systems and the calibration methods for getting rid of distributed targets. In this paper, we contribute to proposing a new and convenient method for estimating the polarimetric channel imbalance phase at the transmitter and receiver, which can be used for both quad-pol and dual-pol SAR systems. We found a brand-new reference object in the urban area scene, namely the effective dihedrals. A statistical calculation method was proposed correspondingly, which obtained an effective estimation of the channel imbalance phases. The theoretical explanation of the proposed method was consistent with the statistical phenomena presented in the experiments. The technique was illustrated and verified through C-band SAR images, including GaoFen-3 (GF-3) data and Sentinel-1 data. The technique was also validated and successfully applied in airborne SAR data of P, L, S, C, and X bands. The estimation error could be within 7° when crosstalk items were less than −30 dB. The method realizes a fast and low-cost dual-polarization phase imbalance estimation and provides a new technical approach to supplement the traditional tropical-rainforest-based quad-pol system calibration. The method can be conveniently applied to the monitoring of polarization distortion parameters, ensuring good polarization SAR data quality. [ABSTRACT FROM AUTHOR]

A dual-polarized, slot-coupled dielectric patch antenna design is presented in sub-6 GHz for 5G base stations. Proposed antenna is implemented using two dielectric patch layers (main patch and parasitic patch) above a feeding line layer. Excitation is realized by crossed elliptic-H slots in order to create orthogonal ± 45? polarizations. Through the use of patches at proper heights together with elliptic-H slots, significant improvement in impedance bandwidth, matching level, isolation and front-to-back ratio is acquired. Prototype antenna has an impedance bandwidth of 18.5% (3.23-3.85 GHz) for |S11|, |S22| < -15 dB, covering the 5G spectra of 3.30-3.80 GHz. The isolation between ports (|S21|) is obtained as < -25 dB in desired operating band. Antenna exhibits stable, broadside radiation patterns with half power beam-widths of 59° -64° and 69° -72° in E/H-planes, respectively. Gain of the antenna varies within the range of 7.9-8.4 dBi. Proposed antenna is also low profile (9.8 mm). It needs no reflector or cavity-backed structure and meets all the requirements of 5G base stations as an antenna element. Design details, numerical studies, and experimental results are presented. [ABSTRACT FROM AUTHOR]

This article presents a ± 45° dual-polarized triple-band dipole antenna array for 5G base station applications. Each antenna element consists of three main parts: radiator, feeding baluns, and reflector. The profile antenna array is designed to cover two bands from n77 and one band from n79 5G NR frequency spectrum. The proposed antenna element and array are optimized with ANSYS 18.2 HFSS simulator and then fabricated and fully characterized. The obtained measured impedance bandwidths resulted in 3.6–3.75 GHz, 4.1–4.25 GHz, and 4.82–4.95 GHz, with a gain of almost 8.12 dBi and 70.7° half-power beam width (HPBW). Once characterized, such an elementary element has been used in the design, realization and test of a 1 × 8 antenna array that exhibited a measured gain 16.65 dBi with 69° HPBW respectively. The antenna array operates in 3.43–3.75 GHz, 4.13–4.30 GHz, and 4.80–4.95 GHz with 15 dB return loss. The triple-band dual-polarized feature with very high isolation, cross-polarization discrimination ratio (XPD) and front to back ratio (FBR) makes this profile antenna array a suitable candidate for 5G base station applications. [ABSTRACT FROM AUTHOR]

article shows a splicable dual-pol. ultra-wideband array antenna used in large-scale arrays. An unequal-spaced metal bullet structure is used as the basic antenna element, and the gradual slot for radiation is spliced by the metal bullet radiator. The bullet structure is directly and vertically interconnected through elastic RF connectors. The antenna structure can be independently installed on the metal backplane and positioned through the slots on the metal backplane to ensure good electrical performance. Compared with the antenna structure processed by PCB technology, this type of antenna can effectively avoid the generation of surface wave modes, thereby ensuring that there is no VSWR singularity in the broadband. The proposed antenna array can realize ±45°scanning in azimuth plane and ±35°scanning in elevation plane within four octave bands. Based on the proposed antenna, a 10*10 prototype was tested. The measured results were consistent with the simulation results. [ABSTRACT FROM AUTHOR]

An antenna-in-package (AiP) of endfire and dual-polarization at 28 GHz is presented. It is formed by four periodic antennas of broad bandwidth and high-isolation, fabricated by the low-temperature cofired ceramics technology. The dual-polarizations are realized by integrating a horizontal metal stripline-coupled dipole with a vertical magneto-electric monopole, incorporated into a multilayer architecture for compactness. The AiP skillfully implements vertical vias and horizontal strip lines in the cavities between antennas to improve isolation and polarization purity. This AiP has numerically been examined for endfire high gain and beam steering in user equipment (UE) applications. The prototype was measured to show good isolation lower than −25 dB from 26.5 to 29.5 GHz and agree with full-wave simulations. The antenna array is finally integrated with 1 $\times $ 4 boresight radiation microstrip antennas to form a complete UE AiP. [ABSTRACT FROM AUTHOR]

A novel dual‐band dual‐polarization Fabry‐Pérot resonator antenna (FPRA) is presented, which is composed of double‐layer frequency selective surfaces (FSS1 and FSS2) and planar patch antenna. By analyzing the passband and stopband characteristics of the FSS1 and the FSS2, it is revealed that FSS1 has stopband characteristic for low frequency and passband characteristic for high frequency, while FSS2 shows stopband characteristic for high frequency and passband characteristic for low frequency. Based on these traits, the gain is improved by the high‐reflection coefficient of FSS1 at low frequency. The linear to circular polarization (CP) conversion is achieved by FSS2 at high frequency. To verify the performance of this proposed design, a prototype FPRA is fabricated and measured. The measurement results show that the peak gain of antenna reaches 16.1 dBic with CP at 9.4 GHz and 15.3 dBi with linear polarization at 5.6 GHz. The measured 3‐dB gain bandwidths is from 5.35 GHz to 5.8 GHz in the lower band, and the combined fractional bandwidth (−10 dB impedance matching, 3‐dB measured gain, and 3‐dB axial ratio) from 9.27 to 9.55 GHz in the upper band is achieved. [ABSTRACT FROM AUTHOR]

This article describes a compact dual-polarized endfire antenna array for fifth-generation (5G) millimeter-Wave (mm-Wave) mobile application. The dual-polarized endfire antenna element is constructed by a compact open-ended cavity with cavity mode for vertical polarization (VP) radiation and open-slot mode for horizontal polarization (HP) radiation. With the integrated design of VP and HP elements, the proposed antenna shows a much more compact size compared to existing schemes. To enhance the bandwidth of low-profile VP radiation, a slot is etched on the cavity to create a new mode for dual-resonance response, realizing a wide bandwidth of 24.5–29.5 GHz for both polarizations. In addition, radiation pattern modification techniques are employed to achieve good endfire beams with a high front-to-back ratio for both polarizations, thus enabling a high peak gain of 10.3 and 11.3 dBi for VP and HP, respectively. A wide beam scanning range of ±50° with realized gain above 7 dBi is realized at 27 GHz for both polarizations. In virtue of compact size, wide bandwidth, high gain, and good spatial coverage, the proposed design strategy is promising for future 5G mm-Wave mobile phones. [ABSTRACT FROM AUTHOR]

In this paper, a dual-polarization weather radar echo signal simulation method is proposed for the evaluation of the performance enhancement of dual-polarization weather radar systems, the optimization of signal processing algorithms and the improvement of scanning strategies. The actual weather radar base data are used in the simulation as the reference weather scene, which avoids using a complex algorithm for weather modeling. Moreover, based on radar weather equations, the radar system parameters are added into the radar echo signal modeling to establish the relationship between the simulated echo signal and radar system. As a result, the final simulated echo signal not only shows both the time and frequency domain characteristics of the weather target, but also includes the effects of the important performance of the dual-polarization weather radar system. In addition, to evaluate the performance of range ambiguity mitigation using phase coding and batch working modes, two different simulation methods for the radar signal are established on the method above; one is for batch working mode with long-PRT (pulse repetition time) and short-PRT transmission and receiving, and the other is for phase-coded mode with phase-coded transmission and phase-uncoded receiving. Under the same weather scene, the observation of these two different methods of range ambiguity mitigation are simulated and compared. Results show that the performance of the phase coding mode for mitigating range ambiguity is better than that of the batch mode. Obviously, the simulation method can be used to directly show the observation of different algorithms for mitigation range ambiguity under the same weather process, and quickly compare and evaluate the algorithm's performance, which is not possible for real radars. [ABSTRACT FROM AUTHOR]

This article presents a shared-aperture dual-band dual-polarized antenna array for fifth-generation (5G) mobile communication. Within one radiating aperture, four higher band (HB) patch antenna elements are placed over the lower band (LB) full-wavelength slot antenna. The proposed array is miniaturized by bending the ground plane of the slot antenna. Suppression of cross-band mutual coupling and scattering is achieved by using the filtering performance of the slot antenna and a dual-function metasurface. The filtering performance of the slot antenna is realized using coupled microstrip lines inside the radiating slot and open-ended stubs on the feeding lines. The dual-function metasurface operates as an artificial magnetic conductor reflector in the LB and bandpass frequency-selective surface in the HB. By placing the dual-function metasurface behind the slot antenna, the radiation of the slot antenna is enhanced in the LB but not HB, and the negative effect of its HB scattering on the HB antennas is reduced. The working mechanism is explained in detail. The measured and simulated results demonstrate that the proposed array has stable radiation patterns in the bands of 0.69–0.96 and 3.4–3.7 GHz with a high cross-band isolation of over 32 dB and is more compact than the previous works. [ABSTRACT FROM AUTHOR]

This article presents a comprehensive analysis of the terahertz (THz) rectification process with modern high-speed silicon–germanium (SiGe) heterojunction bipolar transistor (HBT) devices to enable low-power and close-to-optimum detector sensitivity in a near-THz fractional bandwidth. The influence of all major device internal parasitics on the detector responsivity and noise equivalent power (NEP) is analyzed in detail as a function of the device bias point and the operating frequency. By analogy to the cold MOSFET operation, the fundamentals of the detector operating in weak and deep saturation are studied and compared with the forward-active region, indicating its potentially superior NEP performance with a suitable readout path. The antenna’s broadband radio frequency (RF) power coupling aspects are further elaborated and related to the device bias conditions to maximize the internal base–emitter driving voltage. A set of single- and dual-polarized antenna-coupled detectors with close-to-optimum detector operation in a near-THz fractional bandwidth and a state-of-the-art optical performance was implemented in a 0.13- $\mu \text{m}$ SiGe HBT technology with $f_{t}/f_{\text {max}}$ of 350/550 GHz and extensively characterized across 200–1000 GHz to support the underlying analysis. For the forward-active operation, the following maximum optical current responsivity and minimum optical NEP values have been demonstrated: 5 A/W, 1.9 pW/ $\sqrt {\text {Hz}}$ at 300 GHz and 0.65 A/W, 19 pW/ $\sqrt {\text {Hz}}$ at 900 GHz. The corresponding NEP values for deep saturation (with unbiased collector) are 5.1 pW/ $\sqrt {\text {Hz}}$ and 45 pW/ $\sqrt {\text {Hz}}$ but they are largely limited by the noise floor of the consecutive external amplifier. [ABSTRACT FROM AUTHOR]

This communication proposes a novel fully metallic multibeam Luneburg lens antenna that can simultaneously support the radiation of horizontal polarization (H-pol) and vertical polarization (V-pol). The proposed Luneburg lens consists of a parallel plate waveguide with varying spacing and a series of loaded metallic nails with graded heights. Seven OMTs are employed as the feeder. The measured results show that H-pol/V-pol peak gain is higher than 10.9 dBi/13.8 dBi from 28 GHz to 32 GHz. The dual-polarized beam scan loss is lower than 1.1 dB from −48° to +48°. The results show its potential for application in the MMW multibeam and multipolarization system. [ABSTRACT FROM AUTHOR]