Reliability of X-band Dual-polarization Phased Array Radars Through Comparison with an S-band Dual-polarization Doppler Radar

Based on the observations of a squall line on 11 May 2020 and stratiform precipitation on 6 June 2020 from two X-band dual-polarization phased array weather radars(DP-PAWRs)and an S-band dual-polarization Doppler weather radar(CINRAD/SA-D),the data reliability of DP-PAWR and its ability to detect the fine structures of mesoscale weather systems were assessed.After location matching,the observations of DP-PAWR and CINRAD/SA-D were compared in terms of reflectivity(Z_(H)),radial velocity(V),differential reflectivity(Z_(DR)),and specific differential phase(K_(DP)).The results showed that:(1)DP-PAWR has better ability to detect mesoscale weather systems than CINRAD/SAD;the multi-elevation-angles scanning of the RHI mode enables DP-PAWR to obtain a wider detection range in the vertical direction.(2)DP-PAWR’s Z_(H)and V structures are acceptable,while its sensitivity is worse than that of CINRAD/SA-D.The Z H suffers from attenuation and the Z_(H)area distribution is distorted around strong rainfall regions.(3)DP-PAWR’s Z_(DR)is close to a normal distribution but slightly smaller than that of CINRAD/SA-D.The K_(DP)products of DP-PAWR have much higher sensitivity,showing a better indication of precipitation.(4)DP-PAWR is capable of revealing a detailed and complete structure of the evolution of the whole storm and the characteristics of particle phase variations during the process of triggering and enhancement of a small cell in the front of a squall line,as well as the merging of the cell with the squall line,which cannot be observed by CINRAD/SA-D.With its fast volume scan feature and dual-polarization detection capability,DP-PAWR shows great potential in further understanding the development and evolution mechanisms of meso-γ-scale and microscale weather systems.

Recent Progress in Dual-Polarization Radar Research and Applications in China

Dual-polarization(dual-pol)radar can measure additional parameters that provide more microphysical information of precipitation systems than those provided by conventional Doppler radar.The dual-pol parameters have been successfully utilized to investigate precipitation microphysics and improve radar quantitative precipitation estimation(QPE).The recent progress in dual-pol radar research and applications in China is summarized in four aspects.Firstly,the characteristics of several representative dual-pol radars are reviewed.Various approaches have been developed for radar data quality control,including calibration,attenuation correction,calculation of specific differential phase shift,and identification and removal of non-meteorological echoes.Using dual-pol radar measurements,the microphysical characteristics derived from raindrop size distribution retrieval,hydrometeor classification,and QPE is better understood in China.The limited number of studies in China that have sought to use dual-pol radar data to validate the microphysical parameterization and initialization of numerical models and assimilate dual-pol data into numerical models are summarized.The challenges of applying dual-pol data in numerical models and emerging technologies that may make significant impacts on the field of radar meteorology are discussed.

Experimental Research of Dual-Polarization Passive Radar Based on DTTB Signal

The passive radar is a hot research topic. A multi-channel wideband passive radar experimental system is designed and the digital television terrestrial broadcasting (DTTB) signal is chosen to carry out the target detection experiment of civil aviation aircraft. The polarization and spatial filtering methods are used to solve the strong direct path interference suppression problems brought by the receiving system location;combined with the characteristics of DTTB signal, the block length selection interval in the block batch processing method for range-Doppler images calculation is given;the clutter suppression performance is compared through the experimental data receiving from different bistatic polarization channels, the conclusion is different from the monostatic radar and it can guide the passive radar experiment.

Optimal design of a large dual-polarization microstrip reflectarray with China-coverage patterns for satellite communications

A large dual-polarization microstrip reflectarray with China-coverage patterns in two operating bands is designed.To sufficiently compensate for the spatial phase delay differences in two operating bands separately,a three-layer rectangular patch element is addressed,which is suitable for the large dual-polarization reflectarray.Due to the complexly shaped areas and high gain requirements,there are more than 25000 elements in the reflectarray,making it difficult to design,due to more than 150000 optimization variables.First,the discrete fast Fourier transform(DFFT)and the inverse DFFT are used to establish a one-to-one relationship between the aperture distribution and the far field,which lays a foundation for optimizing the shaped-beam reflectarray.The intersection approach,based on the alternating projection,is used to obtain the desired reflection phases of all the elements at some sample frequencies,and a new method for producing a suitable initial solution is proposed to avoid undesired local minima.To validate the design method,a dual-polarization shaped-beam reflectarray with 7569 elements is fabricated and measured.The measurement results are in reasonable agreement with the simulation ones.Then,for the large broadband reflectarray with the minimum differential spatial phase delays in the operating band,an approach for determining the optimal position of the feed is discussed.To simultaneously find optimal dimensions of each element in two orthogonal directions,we establish a new optimization model,which is solved by the regular polyhedron method.Finally,a dual-band dual-polarization microstrip reflectarray with 25305 elements is designed to cover the continent of China.Simulation results show that patterns of the reflectarray meet the China-coverage requirements in two operating bands,and that the proposed optimization method for designing large reflectarrays with complexly shaped patterns is reliable and efficient.

Progress in dual-band dual-polarization shared-aperture SAR antennas

The progress in dual-band dual-polarization(DBDP)shared-aperture antennas for the synthetic aperture radar(SAR)application in the last decade is reviewed.Several designs of DBDP SAR antenna arrays are introduced with their main performances,then their comparison is summarized.In addition,some techniques enhancing DBDP antenna performances are presented.

PROPAGATION EFFECTS AND APPLICATION OF PHASE INFORMATION FOR C-BAND DUAL-POLARIZATION RADAR

As a study on exploiting and popularizing the advanced dual-polarization weather radartechnique in China,the physical mechanism for the propagation effect of the radar wave isdiscussed by using the widely adapted extended boundary condition method,and some theoreticresults are provided for improving rain measurement accuracy.Furthermore,phase information,another important characteristic quantity of microwave,is considered for tapping the potentialitiesof the new meteorological radar system.

Dual-polarization wavelength conversion of 16-QAM signals in a single silicon waveguide with a lateral p-i-n diode[Invited]

A polarization-diversity loop with a silicon waveguide with a lateral p-i-n diode as a nonlinear medium is used to realize polarization insensitive four-wave mixing. Wavelength conversion of seven dual-polarization 16-quadrature amplitude modulation(QAM) signals at 16 GBd is demonstrated with an optical signal-to-noise ratio penalty below 0.7 dB. High-quality converted signals are generated thanks to the low polarization dependence(≤0.5 dB) and the high conversion efficiency(CE) achievable. The strong Kerr nonlinearity in silicon and the decrease of detrimental free-carrier absorption due to the reverse-biased p-i-n diode are key in ensuring high CE levels.

Impact of external optical feedback on the beat notes of dual-polarization fiber lasers

We present a theoretical analysis and an experimental study of the impacts of external optical feedback on dualfrequency fiber lasers. The external optical feedback can effectively suppress the phase noise of the beat notes of dual-frequency fiber lasers, provided some requirements are satisfied. The polarization of the optical feedback is important for the fiber laser's stability, and it can also tune the beat note frequency. A side effect of external optical feedback, as demonstrated in the experiments, is lowering the sensitivity of the dual-frequency fiber laserbased sensors, although such degradation is not obvious.

Dual-polarization multiplexing amorphous Si:H grating couplers for silicon photonic transmitters in the photonic BiCMOS backend of line

In this paper,we report on polarization combining two-dimensional grating couplers(2D GCs)on amorphous Si:H,fabricated in the backend of line of a photonic BiCMOS platform.The 2D GCs can be used as an interface of a hybrid silicon photonic coherent transmitter,which can be implemented on bulk Si wafers.The fabricated 2D GCs operate in the telecom C-band and show an experimental coupling efficiency of−5 dB with a wafer variation of±1.2 dB.Possibilities for efficiency enhancement and improved performance stability in future design generations are outlined and extension toward O-band devices is also investigated.

Over-the-Air Testing for Dual-Polarized MIMO Devices: Setup Design and Validation

Over-the-air(OTA)testing is considered as the only feasible solution to evaluate radio performances of the fifth-generation(5G)wireless devices which feature two important technologies,i.e.,massive multiple-input multiple-output(MIMO)and millimeter-wave(mmWave).The multi-probe anechoic chamber(MPAC)based OTA setup is able to emulate realistic multipath propagation conditions in a controlled manner.This paper investigates an MPAC OTA setup which is capable of evaluating the performances of 5G base stations as the devices-under-test(DUTs)which are equipped with dual-polarized antennas.Both end-to-end setup and probe configuration for the considered MPAC setup will be elaborated.Furthermore,since building a practical MPAC setup is expensive,time-consuming,and error-prone,an endto-end software testbed is established for validation purpose to avoid technical risks before finalizing an MPAC setup.The architecture of the testbed is presented,which can emulate both the channel profiles perceived by the DUT and the physical-layer behaviors of the considered link conforming to 5G new radio(NR)specifications.Results show that the performances under the emulated channel agree well with those under the target channel,validating the accuracy and effectiveness of the MPAC method.

Diversity–Multiplexing Tradeoff and Outage Performance for 2×2 Dual-Polarized Uncorrelated Rice MIMO Channels

In this paper, diversity-multiplexing tradeoff (DMT) curve for 2×2 Dual-Polarized uncorrelated Rice MIMO channels is studied. Exact expressions for statistic information of mutual information exponent are derived. Impacts of channel parameters such as signal to noise ratio (SNR), k-factor and cross polarization discrimination (XPD) on mutual information exponent are analyzed. Compared to conventional single-polarized (SP) Rice MIMO systems, a qualitatively different behavior is observed for DP Rice systems. The work in this paper, allows identifying quantitatively for which channels (k-factor) and SNR levels the use of dual polarization becomes beneficial. Gamma or lognormal distribution are used to describe mutual information component, and a theoretical formulation for finite-SNR DMT curve in 2×2 DP uncorrelated Rice channels is presented for the first time, which is valid in low and medium SNRs when multiplexing gain is larger than 0.75.

Electromagnetic Band Gap Loaded Square Waveguide Band-Pass Filter for Dual-Polarized Application

An Electromagnetic Band Gap (EBG) loaded square waveguide Band-Pass Filter (BPF) is proposed in this paper. It’s simply composed by symmetrically loading periodical metal diaphragms on each wall of a square waveguide. The influences of insert sizes and loading periods on the overall BPF performances are analyzed. Experimental results agree well with those predicted. 6 GHz pass-band with insert loss less than 1 dB, 2.5 GHz stop-band and larger than 25 dB polarization isolation can be obtained. The BPF can be applied in dual-polarized waveguide-based antenna-feed systems.

An enhanced spectral diversity coregistration method for dualpolarimetric Sentinel-1A/B TOPS data

Sentinel-1A/B data are crucial for retrieving numerical information about surface phenomena and processes.Coregistration of terrain observation by progressive scans(TOPS)data is a critical step in its application.TOPS data must be fundamentally co-registered with an accuracy of 0.001 pixels.However,various decorrelation factors due to natural vegetation and seasonal effects affect the coregistration accuracy of TOPS data.This paper proposed an enhanced spectral diversity coregistration method for dual-polarimetric(PolESD)Sentinel-1A/B TOPS data.The PolESD method suppresses speckle noise based on a unified non-local framework in dual-pol Synthetic Aperture Radar(SAR),and extracts the phase of the optimal polarization channel from the denoised polarimetric interferometric coherency matrix.Compared with the traditional ESD method developed for single-polarization data,the PolESD method can obtain more accurate coherence and phase and get more pixels for azimuth-offset estimation.In bare areas covered with low vegetation,the number of pixels selected by PolESD is more than the Boxcar method.It can also correct misregistration more effectively and eliminate phase jumps in the burst edge.Therefore,PolESD will help improve the application of TOPS data in low-coherence scenarios.

Operational Evaluation of the Quantitative Precipitation Estimation by a CINRAD-SA Dual Polarization Radar System

In this paper,a quantitative precipitation estimation based on the hydrometeor classification(HCA-QPE)algorithm was proposed for the first operational S band dual-polarization radar upgraded from the CINRAD/SA radar of China.The HCA-QPE algorithm,localized Colorado State University-Hydrometeor Identification of Rainfall(CSUHIDRO)algorithm,the Joint Polarization Experiment(JPOLE)algorithm,and the dynamic Z-R relationships based on variational correction QPE(DRVC-QPE)algorithm were evaluated with the rainfall events from March 1 to October 30,2017 in Guangdong Province.The results indicated that even though the HCA-QPE algorithm did not use the observed rainfall data for correction,its estimation accuracy was better than that of the DRVC-QPE algorithm when the rainfall rate was greater than 5 mm h-1;and the stronger the rainfall intensity,the greater the QPE improvement.Besides,the HCA-QPE algorithm worked better than the localized CSU-HIDRO and JPOLE algorithms.This study preliminarily evaluated the improved accuracy of QPE by a dual-polarization radar system modified from CINRAD-SA radar.

Rapid-Scan and Polarimetric Phased-Array Radar Observations of a Tornado in the Pearl River Estuary

The strong destructive winds during tornadoes can greatly threaten human life and destroy property.The increasing availability of visual and remote observations,especially by Doppler weather radars,is of great value in understanding tornado formation and issuing warnings to the public.In this study,we present the first documented tornado over water detected by a state-of-the-art dual-polarization phased-array radar(dual-PAR)in China.In contrast to new-generation weather radars,the dual-PAR shows great advantages in tornado detection for its high spatial resolution,reliable polarimetric variables,and rapid-scan strategy.The polarimetric signature of copolar cross-correlation coefficient with anomalously low magnitude appears to be effective for verifying a tornado and thus is helpful for issuing tornado warnings.The Guangdong Meteorological Service has been developing an experimental X-band dual-PAR network in the Pearl River Delta with the goal of deploying at least 40 advanced dual-PARs and other dual-polarization weather radars before 2035.This network is the first quasi-operational X-band dual-PAR network with unprecedented high coverage in the globe.With such high-performance close-range PARs,efficient operational nowcasting and warning services for small-scale,rapidly evolving,and damaging weather(e.g.,tornadoes,localized heavy rainfall,microbursts,and hail)can be expected.

A Novel Kind of Wideband Low-Profile Dielectric Resonator Antenna Suitable for Beam-scanning Applications

In this paper, a low-profile wideband dielectric resonator antenna(DRA) with a very compact planar size is investigated. The antenna consists of a high permittivity dielectric sheet on the top, a low permittivity substrate in the middle, and a probe feeding structure at the bottom. By digging an annular slot in the designated area of the square dielectric sheet, the resonant frequency of fundamental TE111 mode can be effectively increased to be close to the high-order TE131 mode. The two modes can be finally merged together, yielding a wide impedance bandwidth of16.6%. Most importantly, the combination of the two modes is done on the premise of a fixed antenna planar size, which can be very compact and suitable for beam-scanning applications. A probe feeding structure is used to excite the DRA, making the antenna simple and practical to be integrated with other RF circuits. For verification, antenna prototypes with singlefeed linear polarization and differential-feed dual polarization were fabricated and measured. Reasonable agreement between the measured and simulated results is observed.

Ultra-thin,planar,broadband,dual-polarity plasmonic metalens

An ultrathin,planar,broadband metalens composed of metal rectangular split-ring resonators(MRSRRs) has been designed,which shows dual-polarity characteristics for different types of circularly polarized(CP) light incidence.The designed metalens can be considered as the focusing lens and the diverging lens under left-handed CP and right-handed CP light incidence,respectively.The phase discontinuity of the cross-polarized transmission light is produced by optical-axis rotation through modulating two arms’ lengths of the MRSRR.The MRSRR metalens possesses a wavelength-controllable focal length and a relatively larger chromatic aberration compared with the conventional lenses.And the focal length changes from 9 to 7 μm with incident wavelength from 740 to 950 nm.The dual-polarity flat metalens opens a door for new applications of phase discontinuity devices,and it will promote the fabricating capability of on-chip or fiber-embedded optical devices.

A Broadband45°Dual-Polarized Multiple-Input Multiple-Output Antenna for 5G Base Stations with Extra Decoupling Elements

A dual-polarized multiple-input multiple-output(MIMO)antenna is proposed for 5G base stations.Each antenna element consists of two orthogonally placed fan-shaped dipole elements and45°dual-polarized feed-ing structures are used to achieve broadband operation.The resonant frequency of the array element is from 3.3 to 4.2 GHz,which covers the mainstream spectrum allocations of 5G mobile networks.H-shaped coupling elements are used to improve the isolation between the neighboring antenna elements and the mutual coupling is reduced by over 4 dB.The envelope correlation of a 2×2 array is provided for verification.

Polarization-controlled dual resonant lattice Kerker effects

The generalized Kerker effects have attracted increasing interests in recent years due to their abilities to manipulate the far-field properties of metasurfaces.However,the dual-polarized generalized Kerker effect enabling different tailoring of orthogonally-polarized electromagnetic waves has not yet been reported.Herein,we demonstrate polarization-controlled dual resonant lattice Kerker effects in periodic silicon nanodisks.By varying the incident angle,the electric dipole and magnetic dipole surface lattice resonances can spectrally overlap,causing zero reflectance and unitary transmittance,i.e.,the resonant lattice Kerker effect.The incident angle for achieving this effect can be tuned differently for s-and p-polarizations over large regions by varying the nanodisk size or the lattice periods.The proposed dual-polarized resonant lattice Kerker effects open up avenues for polarization-controlled manipulation of the phase and wavefront of light with metasurfaces.

Performance enhancement for antipodal Vivaldi antenna modulated by a high-permittivity metasurface lens

A metasurface unit is designed operating at 2–20 GHz to enhance the gain and radiation performance of an antipodal Vivaldi antenna(AVA).The unit has a simple structure,stable ultra-wideband performance,high permittivity,and can independently modulate two polarization modes electromagnetic waves.We analyze the current distribution on the unit and extract equivalent characteristic parameters to verify the ability of independent modulation on two polarization modes electromagnetic waves.The designed metasurface unit is integrated into the aperture of the AVA and forms the metasurface lens(ML)for guiding the propagation of electromagnetic waves.Two types of ML are proposed and integrated into the AVA to design antennas Ant1 and Ant2.The modulation effect of the lens on the electromagnetic wave is analyzed from the perspective of electric field amplitude and phase,and the final design is obtained.From the optimized design results,the AVA and the proposed Ant2 are fabricated and measured,and the measurement results are in good agreement with the simulation ones.The impedance bandwidth measured by Ant2 basically covers the 2–18 GHz frequency band.Compared with the conventional AVA,the gain of the proposed Ant2 is increased by 0.6–3.7 d B,the sidelobe level is significantly reduced,and the directivity has also been clearly improved.