An Efficient CSI Feedback Scheme for Dual-Polarized MIMO Systems Using Layered Multi-Paths Information

Massive MIMO is one of tile enabling technologies tbr beyond 4G and 5G systems due to its ability to provide beamforming gain and reduce interference Dual-polarized antenna is widely adopted to accommodate a large number of antenna elements in limited space. However, current CSI（channel state information） feedback schemes developed in LTE for conventional MIMO systems are not efficient enough for massive MIMO systems since the overhead increases almost linearly with the number of antenna. Moreover, the codebook for massive MIMO will be huge and difficult to design with the LTE methodology. This paper proposes a novel CSI feedback scheme named layered Multi-paths Information based CSI Feedback （LMPIF）, which can achieve higher spectrum efficiency for dual-polarized antenna system with low feedback overhead. The MIMO channel is decomposed into long term components （multipath directions and amplitudes） and short term components （multipath phases）. The relationship between the two components and the optimal precoder is derived in closed form. To reduce the overhead, different granularities in feedback time have been applied for the long term components and short term components Link and system level simulation results prove that LMPIF can improve performance considerably with low CSI feedback overhead.

Dual-Polarized Slot-Coupled Microstrip Antenna with Very High Isolation

A wideband dual-polarized slot-coupled stacked microstrip antenna with very high isolation and low cross-polarization is presented. To improve isolation between two poiarization ports, the stacked patches are excited by an open-ended and a T-shaped microstrip lines both via two H-shaped slots placed in a ＂T＂ configuration. The measured isolation is better than 40.5 dB over the bandwidth from 8.8 to 9.8 GHz with cross-polarization level less than - 28.5 dB. The measured VSWR ≤ 2 bandwidths reach 20.7 96 and 19.196 at the verrical and horizontal polarization ports, respectively. This antenna is suitable to be used as array elements in spacebome synthetic aperture radars （SAR） and active phased array radars.

Evaluating the Algorithm for Correction of the Bright Band Effects in QPEs with S-, C-and X-Band Dual-Polarized Radars

The bright band, a layer of enhanced radar reflectivity associated with melting ice particles, is a major source of signifi- cant overestimation in quantitative precipitation estimation （QPE） based on the Z-R （reflectivity factor-rain rate） relationship. The effects of the bright band on radar-based QPE can be eliminated by vertical profile of reflectivity （VPR） correction. In this study, we applied bright-band correction algorithms to evaluate three different bands （S-, C- and X-band） of dual-polarized radars and to reduce overestimation errors in Z-R relationship-based QPEs. After the reflectivity was corrected by the algo- rithms using average VPR （AVPR） alone and a combination of average VPR and the vertical profile of the copolar correlation coefficient （AVPR＋CC）, the QPEs were derived. The bright-band correction and resulting QPEs were evaluated in eight precipitation events by comparing to the uncorrected reflectivity and rain-gange observations, separately. The overestimation of Z-R relationship-based QPEs associated with the bright band was reduced after correction by the two schemes for which hourly rainfall was less than 5 mm. For the verification metrics of RMSE （root-mean-square error）, RMAE （relative mean absolute error） and RMB （relative mean bias） of QPEs, averaged over all eight cases, the AVPR method improved from 2.28, 0.94 and 0.78 to 1.55, 0.60 and 0.40, respectively, while the AVPR＋CC method improved to 1.44, 0.55 and 0.30, respectively. The QPEs after AVPR＋CC correction had less overestimation than those after AVPR correction, and similar conclusions were drawn for all three different bands of dual-polarized radars.

Broadband printed antennas and dual-polarized microstrip and waveguide slot antenna arrays

In order to meet the urgent needs in wireless communications, microwave image synthetic aperture radars （SAR）, and electronic warfare systems, this dissertation studies several types of broadband dual-polarized planar antenna elements and arrays, and proposes a few of novel designs with experimental verification. The main accomplishments reported in the dissertation are as follows.

Wideband dual-polarized slot-coupled microstrip array for synthetic aperture radar application

An 8 × 1-element wideband dual-polarized slot-coupled microstrip antenna array with high isolation and low crosspolarization in X-band is presented. The array antenna offers an impedance bandwidth （VSWR≤2） of 23% and 21% for dual polarization ports, respectively. The measured isolation between two polarization ports is better than 35 dB and the measured cross-polarization level below -25 dB in the main beam over the operation frequency band of 9.35 GHz to 9.75 GHz. This array is well suitable for X-band SAR （synthetic aperture radar） antenna apphcation.

Bandwidth-enhanced dual-polarized antenna with improved broadband integrated balun and distributed parasitic element

A bandwidth-enhanced dual-polarized antenna is proposed for 2/3/4/5G applications,which is composed of distributed parasitic elements(DPEs),a main radiator,two improved broadband integrated baluns and a reflector.First,a novel tooth-shape shorted slot line in the improved broadband integrated balun is analyzed to adjust the input impedance of the antenna.Then,DPEs with 2×2 circular plates loading over the main radiator are proposed to improve broadband impedance matching and radiation pattern.By utilizing impedance compensation of the tooth-shaped shorted slot line and the electromagnetic induction of the DPEs,the antenna achieves an enhanced impedance bandwidth and a stable radiation pattern.To verify these ideas,the bandwidth-enhanced dual-polarized antenna was fabricated and measured.The experimental results indicate that the proposed antenna achieves an operating bandwidth of 72.2%(1.69 to 3.60 GHz)with a return loss(RL)less than-15 dB and a port-to-port isolation(ISO)larger than 30 dB.The antenna obtains a half-power beamwidth(HPBW)within(66±5)°and a gain within(9.0±0.6)dBi in the 2/3/4G bands,and an HPBW within(61.5±2.5)°and a gain within(9.8±0.3)dBi in the 5G band.Across the whole band,the cross-polarization discrimination(XPD)and the front-to-back ratio are both larger than 20 dB.

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.

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.

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.

Identification and Removal of Non-meteorological Echoes in Dual-polarization Radar Data Based on a Fuzzy Logic Algorithm

A major issue in radar quantitative precipitation estimation is the contamination of radar echoes by non-meteorological targets such as ground clutter,chaff,clear air echoes etc.In this study,a fuzzy logic algorithm for the identification of non-meteorological echoes is developed using optimized membership functions and weights for the dual-polarization radar located at Mount Sobaek.For selected precipitation and non-meteorological events,the characteristics of the precipitation and non-meteorological echo are derived by the probability density functions of five fuzzy parameters as functions of reflectivity values.The membership functions and weights are then determined by these density functions.Finally,the nonmeteorological echoes are identified by combining the membership functions and weights.The performance is qualitatively evaluated by long-term rain accumulation.The detection accuracy of the fuzzy logic algorithm is calculated using the probability of detection（POD）,false alarm rate（FAR）,and clutter–signal ratio（CSR）.In addition,the issues in using filtered dual-polarization data are alleviated.

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.

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.

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.

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.

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.

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.

Design of broadband dual-polarized antenna with integrated Marchand balun

A design of broadband dual-polarized antenna with low cross polarization and high isolation was presented. The antenna is composed of a cross dipole, a folded ground, two feeding networks, and a reflector. The impedance bandwidth was enhanced by utilizing the mutual coupling between the two dipoles. A kind of meandering folded Marchand balun was skillfully integrated on the support column of the antenna to excite the dipole differentially, which can deliver both balanced （within 0.5 dB） power splitting and consistent （±5°） phase shifting from 1.71 GHz to 2.17 GHz. The standing wave ratios （SWRs） of each port are less than 1.5. By using this feeding network, the antenna has good performance in isolation （〉 45 dB） and cross polarization （〉 30 dB） over the entire operating frequency band. Moreover, the gain （-8.6 dB） of the proposed antenna is stable with frequency and the antenna structure is very firm due to the support column. The proposed antenna can be easily formed an array for digital cellular system （DCS）, personal communications service （PCS） and 3rd generation （3G） applications.

Adaptive cancellation of Es layer interference using auxiliary horizontal antennas

Based on a dual-polarization high-frequency wave radar system, an adaptive system using horizontal antennas for the suppression of the Es layer interference （ELI） is deseribech The data received from the horizontal antennas were correlated with the data received from the Vertically Polarized Antennas （VPAs） to estimate and cancel the interference adaptively in the VPAs. Suppressing the interference after each coherent integration time interval, about 25 dB signal-to-interference ratio is expected with the experimentally derived data.