The assimilation of dual-polarization(dual-pol)radar data plays a crucial role in enhancing the simulation of hydrometeors and improving the short-term precipitation forecasts of numerical weather prediction(NWP)model...The assimilation of dual-polarization(dual-pol)radar data plays a crucial role in enhancing the simulation of hydrometeors and improving the short-term precipitation forecasts of numerical weather prediction(NWP)models.However,existing dual-pol radar data assimilation(DA)methods exhibit limitations in terms of computational efficiency and data utilization.In this study,a new dual-pol radar DA approach is developed that utilizes a UNet-based model to retrieve mixing ratio information for four hydrometeor species from dual-pol radar data.The validation results for the UNet-based model indicate that the distributions of the retrieved hydrometeor mixing ratios provided by the model align well with the labeled data,yielding a reasonable range of root mean square errors(RMSEs).On this basis,the hydrometeor analysis increments retrieved by the UNet-based model are incorporated into the model integration process through the incremental analysis update(IAU)scheme,establishing a complete dual-pol radar DA framework for the CMA-MESO model.To evaluate the efficacy of this DA scheme,comparative simulation experiments were conducted for Typhoon Lekima(2019).Verification results indicate that using the hydrometeor DA scheme generally improves the threat scores(TSs)for 3-hour accumulated precipitation during medium-and heavy-rainfall events.Additionally,the 24-hour accumulated rainfall TSs for the medium-,heavy-,and extreme-precipitation categories in the DA experiment are all superior to those in the control experiment.The DA method also yields superior predictions of the spatial distribution of extremerainfall events.These results demonstrate that the proposed dual-pol radar DA approach effectively enhances the precipitation forecasting capabilities of numerical weather models.展开更多
Numerical models play an important role in convective-scale forecasting,and dual-polarization radar observations can provide detailed microphysical data.In this study,we implement a direct assimilation operator for du...Numerical models play an important role in convective-scale forecasting,and dual-polarization radar observations can provide detailed microphysical data.In this study,we implement a direct assimilation operator for dual-polarization radar data using the hydrometeor background error covariance(HBEC)in the China Meteorological Administration MESO-scale weather forecasting system(CMA-MESO,formerly GRAPES-MESO)and conducted assimilation and forecasting experiments with X-band and S-band dual-polarization radar data on two cases.The results indicate that the direct assimilation of dual-polarization radar data enhanced the microphysical fields and the thermodynamic structure of convective systems to some extent based on the HBEC,thereby improving precipitation forecasts.Among the sensitivity tests of microphysical parameterization schemes,including the LIUMA scheme,the THOMPSON scheme,and the WSM6scheme(WRF Single-Moment 6-class),we find that the greatest improvement in the equivalent potential temperature,relative humidity,wind,and accumulated precipitation forecasts occurred in the experiment using the WSM6 scheme,as the distribution of solid precipitation particles was closer to the hydrometeor classification algorithm from the dualpolarization radar observations in our cases.展开更多
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 weat...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.展开更多
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 be...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.展开更多
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 f...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.展开更多
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 det...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.展开更多
As a study on exploiting and popularizing the advanced dual-polarization weather radar technique in China,the physical mechanism for the propagation effect of the radar wave is discussed by using the widely adapted ex...As a study on exploiting and popularizing the advanced dual-polarization weather radar technique in China,the physical mechanism for the propagation effect of the radar wave is discussed by using the widely adapted extended boundary condition method,and some theoretic results are provided for improving rain measurement accuracy.Furthermore,phase information, another important characteristic quantity of microwave,is considered for tapping the potentialities of the new meteorological radar system.展开更多
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 ...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.展开更多
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 ...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.展开更多
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 h...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.展开更多
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...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.展开更多
In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is com...In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.展开更多
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 ...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.展开更多
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 plan...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.展开更多
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 mult...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.展开更多
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 ...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.展开更多
A tunable dual polarization absorption-transmission-absorption(A-T-A)frequency selective absorbers(FSR)to address the issue of high insertion loss in current tunable FSRs is proposed.The lumped resistors are loaded on...A tunable dual polarization absorption-transmission-absorption(A-T-A)frequency selective absorbers(FSR)to address the issue of high insertion loss in current tunable FSRs is proposed.The lumped resistors are loaded onto the lossy layer to absorb electromagnetic waves within the absorption band.The varactor diodes are loaded onto another lossless layer to control the transmission frequency band of the FSR.Its equivalent circuit model is provided.The proposed tunable FSR can change the passband within the range of 14.5~15.5 GHz by changing the bias voltage applied to the lossless transmission layer,while maintaining insertion loss above-1.67 dB.The series resonant structure of the lossy layer generates bilateral absorption bands between 10.2~13.5 GHz and 17.2~22 GHz,with broadband reflection suppression ranging from 10.3 GHz to 22 GHz(70.7%).The prototype is manufactured,and the measured results have verified the simulation results.展开更多
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 （refl...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.展开更多
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.Firs...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.展开更多
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 num...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.展开更多
基金Major Key Project of PCL(PCL2025A10)Open Research Project of the China Meteorological Administration Hydro-Meteorology Key Laboratory(23SWQXM036)+2 种基金National Natural Science Foundation of China(42375160)Project of the Key Laboratory of Atmospheric Sounding of China Meteorological Administration(2022KLAS06M)Science and Technology Research Project of the Guangdong Provincial Meteorological Bureau(GRMC2024M04)。
文摘The assimilation of dual-polarization(dual-pol)radar data plays a crucial role in enhancing the simulation of hydrometeors and improving the short-term precipitation forecasts of numerical weather prediction(NWP)models.However,existing dual-pol radar data assimilation(DA)methods exhibit limitations in terms of computational efficiency and data utilization.In this study,a new dual-pol radar DA approach is developed that utilizes a UNet-based model to retrieve mixing ratio information for four hydrometeor species from dual-pol radar data.The validation results for the UNet-based model indicate that the distributions of the retrieved hydrometeor mixing ratios provided by the model align well with the labeled data,yielding a reasonable range of root mean square errors(RMSEs).On this basis,the hydrometeor analysis increments retrieved by the UNet-based model are incorporated into the model integration process through the incremental analysis update(IAU)scheme,establishing a complete dual-pol radar DA framework for the CMA-MESO model.To evaluate the efficacy of this DA scheme,comparative simulation experiments were conducted for Typhoon Lekima(2019).Verification results indicate that using the hydrometeor DA scheme generally improves the threat scores(TSs)for 3-hour accumulated precipitation during medium-and heavy-rainfall events.Additionally,the 24-hour accumulated rainfall TSs for the medium-,heavy-,and extreme-precipitation categories in the DA experiment are all superior to those in the control experiment.The DA method also yields superior predictions of the spatial distribution of extremerainfall events.These results demonstrate that the proposed dual-pol radar DA approach effectively enhances the precipitation forecasting capabilities of numerical weather models.
基金sponsored by the National Natural Science Foundation of China(U2442601 and U2442218)the High Performance Computing Platform of Nanjing University of Information Science&Technology(NUIST)for their support of this work。
文摘Numerical models play an important role in convective-scale forecasting,and dual-polarization radar observations can provide detailed microphysical data.In this study,we implement a direct assimilation operator for dual-polarization radar data using the hydrometeor background error covariance(HBEC)in the China Meteorological Administration MESO-scale weather forecasting system(CMA-MESO,formerly GRAPES-MESO)and conducted assimilation and forecasting experiments with X-band and S-band dual-polarization radar data on two cases.The results indicate that the direct assimilation of dual-polarization radar data enhanced the microphysical fields and the thermodynamic structure of convective systems to some extent based on the HBEC,thereby improving precipitation forecasts.Among the sensitivity tests of microphysical parameterization schemes,including the LIUMA scheme,the THOMPSON scheme,and the WSM6scheme(WRF Single-Moment 6-class),we find that the greatest improvement in the equivalent potential temperature,relative humidity,wind,and accumulated precipitation forecasts occurred in the experiment using the WSM6 scheme,as the distribution of solid precipitation particles was closer to the hydrometeor classification algorithm from the dualpolarization radar observations in our cases.
基金Guangdong Basic and Applied Basic Research Foundation(2020A1515010602)Special Fund of China Meteorological Administration for Innovation and Development(CXFZ2022J063)+4 种基金Special Fund for Forecasters of China Meteorological Administration(CMAYBY2019-082)Science and Technology Planning Program of Guangzhou(201903010101)Key-Area Research and Development Program of Guangdong Province(2020B1111200001)National Natural Science Foundation of China(42075190,41875182)Radar Application and Shortterm Severe-weather Predictions and Warnings Technology Program(GRMCTD202002)。
文摘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.
基金primarily supported by the National Key Research and Development Program of China(Grant Nos.2017YFC1501703 and 2018YFC1506404)the National Natural Science Foundation of China(Grant Nos.41875053,41475015 and 41322032)+2 种基金the National Fundamental Research 973 Program of China(Grant Nos.2013CB430101 and2015CB452800)the Open Research Program of the State Key Laboratory of Severe Weatherthe Key Research Development Program of Jiangsu Science and Technology Department(Social Development Program,No.BE2016732)
文摘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.
基金supported by a grant(14AWMP-B079364-01) from Water Management Research Program funded by Ministry of Land,Infrastructure and Transport of Korean government
文摘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.
文摘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.
文摘As a study on exploiting and popularizing the advanced dual-polarization weather radar technique in China,the physical mechanism for the propagation effect of the radar wave is discussed by using the widely adapted extended boundary condition method,and some theoretic results are provided for improving rain measurement accuracy.Furthermore,phase information, another important characteristic quantity of microwave,is considered for tapping the potentialities of the new meteorological radar system.
基金supported by the National Key Research and Development Program of China(No.2017YFB0202102)。
文摘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.
基金supported by the National High-Technology Research and Development (863)Project of China (No.2007AA12Z125)the National Natural Science Foundation of China (Grant No.60871030)the Specialized Research Fund of Doctoral Programs,Ministry of Education of China (No.20050280016).
文摘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.
基金This work was supported in part by the German Research Foundation(DFG)through the projects EPIC-Sense(ZI 1283-6-1)EPIDAC(ZI 1283-7-1)the Federal Ministry of Education and Research(BMBF)through project PEARLS(13N14932).
文摘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.
文摘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.
基金supported by ZTE Industry-University-Institute Cooperation Funds under Grant No.HC-CN-20220719005。
文摘In this paper,a dual-polarized antenna operating at 3.5 GHz is presented with 2D beam-scanning performance.The steerable beam is realized based on a 2×2 active reflective metasurface.The active metasurface is composed of folded annular rings and cross dipoles embedded with voltage-controlled varactor diodes.By tuning the capacitance values of the varactors,the reflective phase of the metasurface is reconfigured to tilt the main beam.To verify the scanning performance,a prototype is fabricated and measured.At 3.5 GHz,the measured scanning ranges are from-25°to 29°and-27°to 29°in the XOZ and YOZ planes,respectively.
文摘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.
文摘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.
基金supported by the National Natural Science Foundation of China under Grant.61971067.
文摘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.
基金Project supported by the Specialized Research Fund for the Doctoral Program of High Education of China (Grant No.20050280016)the Shanghai Leading Academic Discipline Project (Grant No.T0102)
文摘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.
文摘A tunable dual polarization absorption-transmission-absorption(A-T-A)frequency selective absorbers(FSR)to address the issue of high insertion loss in current tunable FSRs is proposed.The lumped resistors are loaded onto the lossy layer to absorb electromagnetic waves within the absorption band.The varactor diodes are loaded onto another lossless layer to control the transmission frequency band of the FSR.Its equivalent circuit model is provided.The proposed tunable FSR can change the passband within the range of 14.5~15.5 GHz by changing the bias voltage applied to the lossless transmission layer,while maintaining insertion loss above-1.67 dB.The series resonant structure of the lossy layer generates bilateral absorption bands between 10.2~13.5 GHz and 17.2~22 GHz,with broadband reflection suppression ranging from 10.3 GHz to 22 GHz(70.7%).The prototype is manufactured,and the measured results have verified the simulation results.
基金funded by a China National 973 Program on Key Basic Research project (Grant No.2014CB441401)the Beijing Municipal Natural Science Foundation (Grant No.8141002)the Public Welfare Industry (Meteorology) of China (Grant No.GYHY201106046)
文摘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.
基金The National Natural Science Foundation of China(No.61471117).
文摘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.
基金supported by the National High-Tech R&D Program(863 Program 2015AA01A705)
文摘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.
