An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy....An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.展开更多
The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment.Extensive experiments and numerous studies are being conducted to develop com...The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment.Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy.Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs.A novel high-gradient structure with a low relativistic proton velocity(β),v/c=0.38,was designed,fabricated,and tested at high power.The first full-scale prototype was also successfully tested with high radio frequency(RF)power,a repetition rate of 50 Hz,and pulse length of 3μs to reach a high-gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility.This is the first high-power test in China,which is in line with the expected experimental goal.This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells.This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities.The cold test of the prototype cavity was completed in advance.Details of the high-power RF test setup,the process of RF conditioning,and the high-power results are described.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
This letter reports the development of a 50MW S-band klystron in the Institute of Electronics, Chinese Academy of Sciences （IECAS）. It adopted a structure of six-cavity and single output window. Under conditions of ...This letter reports the development of a 50MW S-band klystron in the Institute of Electronics, Chinese Academy of Sciences （IECAS）. It adopted a structure of six-cavity and single output window. Under conditions of an RF （Radio Frequency） pulse width of 4t, ts, a beam voltage of 305,9kV and a beam current of 368A, the peak output power has achieved 51.4MW with an efficiency of 45.6% and a gain of 54dB.展开更多
This letter introduces the design ideas, simulation and test results of an S-band klystron with bandwidth of 11%, which was developed by the Institute of Electronics, Chinese Academy of Sciences (IECAS). On the peak p...This letter introduces the design ideas, simulation and test results of an S-band klystron with bandwidth of 11%, which was developed by the Institute of Electronics, Chinese Academy of Sciences (IECAS). On the peak power level of 800 kW, the efficiency of klystron is more than 30%; the gain is more than 41 dB; the equal-driving relative instantaneous bandwidth is over 11%; the average power is larger than 8 kW, and the power fluctuation within bandwidth is less than 1.5 dB.展开更多
We have observed weather clutter containing targets (ships) using an S-band radar with a frequency 3.05 GHz, a beam width 1.8°, and a pulsewidth 0.5 μs. To investigate the weather clutter amplitude statistics, w...We have observed weather clutter containing targets (ships) using an S-band radar with a frequency 3.05 GHz, a beam width 1.8°, and a pulsewidth 0.5 μs. To investigate the weather clutter amplitude statistics, we introduce the Akaike Information Criterion (AIC). We have found that the weather clutter amplitudes obey the log-normal, Weibull, and log-Weibull distributions with the shape parameters of 0.308 to 0.470, 4.42 to 4.51, and 15.91 to 16.44, respectively, for small data within the beam width of an antenna. We have proposed the log-normal/CFAR circuit modified a Cell-Averaging (CA) LOG/CFAR circuit. It is found that weather clutter is suppressed with improvement of 51.58 dB by log-normal/CFAR. As a result, we have showed that weather clutter observed by S-band radar does not obey the Rayleigh distribution and our log-normal/CFAR circuit has an effect on suppression of clutter and detection of target, while conventional LOG/CFAR circuit does not. In addition, if our circuit can be realized, we will have an advantage economically.展开更多
In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplific...In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.展开更多
Single metal atoms anchored on nitrogen-doped carbon materials(M-N_(4))have been identified as effective active sites for catalyzing the two-electron oxygen reduction reaction(2e-ORR).However,the relationship between ...Single metal atoms anchored on nitrogen-doped carbon materials(M-N_(4))have been identified as effective active sites for catalyzing the two-electron oxygen reduction reaction(2e-ORR).However,the relationship between the local atomic/electronic environments of the M-N_(4)sites(metal atoms coordinated with different types of N species)and their catalytic activity for 2e-ORR has rarely been elaborated clearly,which imposes significant ambiguity for the rational design of catalysts.Herein,guided by the comprehensive density-functional theory calculations and predictions,a series of Zn-N_(4)single-atom catalysts(SACs)are designed with pyrrole/pyridine-N(N_(Po)/N_(Pd))synergistic coordination and prepared by controlling the pyrolysis temperature(600,700,and 800℃),Among them,the dominated Zn-N_(4)configurations with rationally combined N_(Po)/N_(Pd)coordination show~*OOH adsorption strength close to the optimal value,much superior to those with mono N species.Thus,the as-prepared catalyst exhibits a high H_(2)O_(2)selectivity of over 90%both in neutral and alkaline environments,with a superb H_(2)O_(2)yield of up to 33.63 mol g^(-1)h^(-1)in an alkaline with flow cell.More importantly,a new descriptor,dz^(2)+s band center,has been proposed,which is especially feasible for predicting the activity for metal types with fully occupied s and d orbitals.This work thus presents clear guidance for the rational design of highly active SACs toward ORR and provides a complement to the d-band theory for more accurately predicting the catalytic activity of the materials.展开更多
This paper presents the model cavity tune and cold test of an S-band 2MeV on-axis coupling SW accelerator. The measurement of the model cavity's frequency,degree of coupling,Q value and on-axis field distribution ...This paper presents the model cavity tune and cold test of an S-band 2MeV on-axis coupling SW accelerator. The measurement of the model cavity's frequency,degree of coupling,Q value and on-axis field distribution are described in detail.In addition,the results of cavity tune and cold test of the accelerating tube are given.The frequency consistency of the accelerator is within±0.3MHz,the coupling degree in the supersaturation state 1.14,the quality factor of the accelerator 12000±200,and the field distribution ratio 1:2.2:2.All the results observed show that the accelerator satisfies the physics design with microwave debugging.展开更多
为更好地对S/X波段天气雷达组网融合在广西区域的应用能力进行评估,利用雷达观测资料,依次进行基数据解析、Z_(H)-K_(DP)综合法衰减订正、单站雷达网格化及多部雷达组网拼图,最终利用组合反射率、等高平面反射率对广西现有雷达组网覆盖...为更好地对S/X波段天气雷达组网融合在广西区域的应用能力进行评估,利用雷达观测资料,依次进行基数据解析、Z_(H)-K_(DP)综合法衰减订正、单站雷达网格化及多部雷达组网拼图,最终利用组合反射率、等高平面反射率对广西现有雷达组网覆盖能力在2023年第4号台风“泰利”影响过程进行初步应用分析。结果显示:结合径向廓线对比、网格化对比及多个连续体扫得到的反射率对比分析,经过Z_(H)-K_(DP)综合法订正后的X波段天气雷达反射率在一定范围内具有较高的可靠性;将组网拼图结果应用于台风“泰利”暴雨过程分析,对比S波段和S/X波段天气雷达组网后的0.5 km、0.75 km、1.0 km和2.0 km CAPPI(Constant Altitude Plan Position Indicator)组网反射率因子覆盖区域,结果显示X波段加入雷达组网后,得到了空间结构连续、覆盖更广的资料,有效补充了广西新一代天气雷达的低层盲区、阻挡空缺区等。展开更多
According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval...According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval of rain drop size distributions （DSDs） from Guangzhou S-band polarimetric radar observations. Two typical precipitation processes were selected to verify the accuracy of the retrieval scheme. The p-A relationship： A = 0.0241μ^2 ＋ 0.867μ ＋ 2.453 was obtained based on the 2DVD observation results from at Huizhou Longmen station, which is a very representat-ive location in the area. Relying on the Guangzhou polarimetric radar measurements of radar reflectivity （ZHH） and differential reflectivity （ZDR）, the gamma （F） size distribution parameters （No, μ, and A） can be retrieved by the C-G model retrieval scheme. The results show that the Guangzhou polarimetric radar retrievals of DSDs were close to the 2DVD observations at Guangzhou Maofengshan station. The rain rate, mass mean diameter, and normalized inter-cept parameter of radar retrievals were in good agreement with the 2DVD observations, and the relative errors were less than 10%. The overall accuracy of the retrieval scheme was high. The retrieval scheme has established the rela-tionship between the polarimetric radar measurements and gamma size distribution parameters. It will be helpful to in-depth research and application of the dual-polarization radar data in microphysical precipitation processes analysis, as well as convection-resolved numerical model data assimilation and prediction effect evaluation.展开更多
A broadband class-F power amplifier for an S-band handset device is integrated on a 330.82 mm^3 die using an In Ga /GaAs HBT process. With LC serial harmonic traps immersed into the broadband output matching circuit, ...A broadband class-F power amplifier for an S-band handset device is integrated on a 330.82 mm^3 die using an In Ga /GaAs HBT process. With LC serial harmonic traps immersed into the broadband output matching circuit, good harmonic suppression performance can be achieved. A pure resistive impedance of the matching circuit, but near zero at second and infinite at third harmonic frequency, which enhances the efficiency, is obtained across 1.8–2.5 GHz. Tested with a continuous wave（CW） signal, the PA delivers an output power of 34 dBm and achieves a PAE of 57% at 2 GHz. In addition, excellent harmonic suppression levels of less than –53 dBc across the second to fifth harmonic are obtained.展开更多
Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system assemblies.However,the peak powers of these waveguides have...Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system assemblies.However,the peak powers of these waveguides have been limited to several megawatts in non-vacuum environments.Herein,a novel flexible waveguide was developed for the S-band(2856 MHz)with the aim of facilitating the interconnection of two hard waveguides.Methods The flexible waveguide was composed of brass,and its surface was plated with oxygen-free high-conductivity copper for brazing with stainless steel flanges in a vacuum furnace.By connecting the stainless steel flanges together,it can be applied to a high-vacuum environment.Results The prototype exhibited good measurement results in low-power microwave tests;the results of a 72-h vacuum leak test showed satisfactory vacuum performance as well,and no obvious surface collapse was observed.High-power microwave commissioning was conducted between June and July 2019;the waveguide showed a maximum average power of approximately 2.7 kW.Conclusion Unfortunately,the prototype was damaged after reaching that power level,which indicates the need for further optimization of the fabrication process.From our experiment,it is clear that the flexible waveguide cannot be used in large accelerators because of its average power limit.展开更多
基金This work was supported by the Alliance of International Science Organizations(No.ANSO-CR-KP-2020-16).
文摘An S-band high-gradient accelerating structure is designed for a proton therapy linear accelerator(linac)to accommodate the new development of compact,singleroom facilities and ultra-high dose rate(FLASH)radiotherapy.To optimize the design,an efficient optimization scheme is applied to improve the simulation efficiency.An S-band accelerating structure with 2856 MHz is designed with a low beta of 0.38,which is a difficult structure to achieve for a linac accelerating proton particles from 70 to 250 MeV,as a high gradient up to 50 MV/m is required.A special design involving a dual-feed coupler eliminates the dipole field effect.This paper presents all the details pertaining to the design,fabrication,and cold test results of the S-band high-gradient accelerating structure.
基金supported by National Key R&D Program of China(No.2018YFF0109203)。
文摘The development of a high-gradient accelerating structure is underway to construct a compact proton linear accelerator for cancer treatment.Extensive experiments and numerous studies are being conducted to develop compact linear accelerators for proton therapy.Optimization of the electromagnetic and mechanical design has been performed to simplify the manufacturing process and reduce costs.A novel high-gradient structure with a low relativistic proton velocity(β),v/c=0.38,was designed,fabricated,and tested at high power.The first full-scale prototype was also successfully tested with high radio frequency(RF)power,a repetition rate of 50 Hz,and pulse length of 3μs to reach a high-gradient of 46 MV/m using a 50 MW S-band klystron power supply obtained from the Shanghai Soft X-ray Free Electron Laser Facility.This is the first high-power test in China,which is in line with the expected experimental goal.This study presents preliminary high-power testing of S-band standing wave accelerating structures with 11 cells.This work aims to verify the feasibility of using a high-gradient RF accelerating structure in compact proton therapy facilities.The cold test of the prototype cavity was completed in advance.Details of the high-power RF test setup,the process of RF conditioning,and the high-power results are described.
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.
文摘This letter reports the development of a 50MW S-band klystron in the Institute of Electronics, Chinese Academy of Sciences （IECAS）. It adopted a structure of six-cavity and single output window. Under conditions of an RF （Radio Frequency） pulse width of 4t, ts, a beam voltage of 305,9kV and a beam current of 368A, the peak output power has achieved 51.4MW with an efficiency of 45.6% and a gain of 54dB.
文摘This letter introduces the design ideas, simulation and test results of an S-band klystron with bandwidth of 11%, which was developed by the Institute of Electronics, Chinese Academy of Sciences (IECAS). On the peak power level of 800 kW, the efficiency of klystron is more than 30%; the gain is more than 41 dB; the equal-driving relative instantaneous bandwidth is over 11%; the average power is larger than 8 kW, and the power fluctuation within bandwidth is less than 1.5 dB.
文摘We have observed weather clutter containing targets (ships) using an S-band radar with a frequency 3.05 GHz, a beam width 1.8°, and a pulsewidth 0.5 μs. To investigate the weather clutter amplitude statistics, we introduce the Akaike Information Criterion (AIC). We have found that the weather clutter amplitudes obey the log-normal, Weibull, and log-Weibull distributions with the shape parameters of 0.308 to 0.470, 4.42 to 4.51, and 15.91 to 16.44, respectively, for small data within the beam width of an antenna. We have proposed the log-normal/CFAR circuit modified a Cell-Averaging (CA) LOG/CFAR circuit. It is found that weather clutter is suppressed with improvement of 51.58 dB by log-normal/CFAR. As a result, we have showed that weather clutter observed by S-band radar does not obey the Rayleigh distribution and our log-normal/CFAR circuit has an effect on suppression of clutter and detection of target, while conventional LOG/CFAR circuit does not. In addition, if our circuit can be realized, we will have an advantage economically.
文摘In this paper,we present the general design methods and parameter measurements of a 1-k W solidstate radio frequency(RF) power amplifier at 2856 MHz,for the soft X-ray free electron laser facility.Three-stage amplification with a 4-way combination is used.An RF switch module is integrated with the solid-state RF power amplifier to convert the continuous wave(CW) signal into pulse signal,with adjustable pulse width.The power gain is measured at 57.7 d B at 60 d Bm output.The RF phase noise,which is measured by the low-level RF system,is\0.015 degree(RMS),while the pulse frontier jitter is\5 ns.
基金National Natural Science Foundation of China(No.22379111 and 22179093)。
文摘Single metal atoms anchored on nitrogen-doped carbon materials(M-N_(4))have been identified as effective active sites for catalyzing the two-electron oxygen reduction reaction(2e-ORR).However,the relationship between the local atomic/electronic environments of the M-N_(4)sites(metal atoms coordinated with different types of N species)and their catalytic activity for 2e-ORR has rarely been elaborated clearly,which imposes significant ambiguity for the rational design of catalysts.Herein,guided by the comprehensive density-functional theory calculations and predictions,a series of Zn-N_(4)single-atom catalysts(SACs)are designed with pyrrole/pyridine-N(N_(Po)/N_(Pd))synergistic coordination and prepared by controlling the pyrolysis temperature(600,700,and 800℃),Among them,the dominated Zn-N_(4)configurations with rationally combined N_(Po)/N_(Pd)coordination show~*OOH adsorption strength close to the optimal value,much superior to those with mono N species.Thus,the as-prepared catalyst exhibits a high H_(2)O_(2)selectivity of over 90%both in neutral and alkaline environments,with a superb H_(2)O_(2)yield of up to 33.63 mol g^(-1)h^(-1)in an alkaline with flow cell.More importantly,a new descriptor,dz^(2)+s band center,has been proposed,which is especially feasible for predicting the activity for metal types with fully occupied s and d orbitals.This work thus presents clear guidance for the rational design of highly active SACs toward ORR and provides a complement to the d-band theory for more accurately predicting the catalytic activity of the materials.
文摘This paper presents the model cavity tune and cold test of an S-band 2MeV on-axis coupling SW accelerator. The measurement of the model cavity's frequency,degree of coupling,Q value and on-axis field distribution are described in detail.In addition,the results of cavity tune and cold test of the accelerating tube are given.The frequency consistency of the accelerator is within±0.3MHz,the coupling degree in the supersaturation state 1.14,the quality factor of the accelerator 12000±200,and the field distribution ratio 1:2.2:2.All the results observed show that the accelerator satisfies the physics design with microwave debugging.
文摘为更好地对S/X波段天气雷达组网融合在广西区域的应用能力进行评估,利用雷达观测资料,依次进行基数据解析、Z_(H)-K_(DP)综合法衰减订正、单站雷达网格化及多部雷达组网拼图,最终利用组合反射率、等高平面反射率对广西现有雷达组网覆盖能力在2023年第4号台风“泰利”影响过程进行初步应用分析。结果显示:结合径向廓线对比、网格化对比及多个连续体扫得到的反射率对比分析,经过Z_(H)-K_(DP)综合法订正后的X波段天气雷达反射率在一定范围内具有较高的可靠性;将组网拼图结果应用于台风“泰利”暴雨过程分析,对比S波段和S/X波段天气雷达组网后的0.5 km、0.75 km、1.0 km和2.0 km CAPPI(Constant Altitude Plan Position Indicator)组网反射率因子覆盖区域,结果显示X波段加入雷达组网后,得到了空间结构连续、覆盖更广的资料,有效补充了广西新一代天气雷达的低层盲区、阻挡空缺区等。
基金Supported by the National(Key)Basic Research and Development(973)Program of China(2015CB452802)Natrional Key Research and Development Program of China(2017YFC1501701)+3 种基金National Natural Science Foundation of China(41475102,41705020,and 41705120)China Meteorological Administration Special Public Welfare Research Fund(GYHY201406013)Guangdong Province Science and Technology Project(2015B020217001)Natural Science Foundation of Guangdong Province(2016A030313141)
文摘According to the statistical shape-slope （μ-A） relationship observed for the first time by several 2D-Video-Distro-meters （2DVD） in southern China, a constrained gamma （C-G） model was proposed for the retrieval of rain drop size distributions （DSDs） from Guangzhou S-band polarimetric radar observations. Two typical precipitation processes were selected to verify the accuracy of the retrieval scheme. The p-A relationship： A = 0.0241μ^2 ＋ 0.867μ ＋ 2.453 was obtained based on the 2DVD observation results from at Huizhou Longmen station, which is a very representat-ive location in the area. Relying on the Guangzhou polarimetric radar measurements of radar reflectivity （ZHH） and differential reflectivity （ZDR）, the gamma （F） size distribution parameters （No, μ, and A） can be retrieved by the C-G model retrieval scheme. The results show that the Guangzhou polarimetric radar retrievals of DSDs were close to the 2DVD observations at Guangzhou Maofengshan station. The rain rate, mass mean diameter, and normalized inter-cept parameter of radar retrievals were in good agreement with the 2DVD observations, and the relative errors were less than 10%. The overall accuracy of the retrieval scheme was high. The retrieval scheme has established the rela-tionship between the polarimetric radar measurements and gamma size distribution parameters. It will be helpful to in-depth research and application of the dual-polarization radar data in microphysical precipitation processes analysis, as well as convection-resolved numerical model data assimilation and prediction effect evaluation.
文摘A broadband class-F power amplifier for an S-band handset device is integrated on a 330.82 mm^3 die using an In Ga /GaAs HBT process. With LC serial harmonic traps immersed into the broadband output matching circuit, good harmonic suppression performance can be achieved. A pure resistive impedance of the matching circuit, but near zero at second and infinite at third harmonic frequency, which enhances the efficiency, is obtained across 1.8–2.5 GHz. Tested with a continuous wave（CW） signal, the PA delivers an output power of 34 dBm and achieves a PAE of 57% at 2 GHz. In addition, excellent harmonic suppression levels of less than –53 dBc across the second to fifth harmonic are obtained.
基金Funded by Youth Innovation Promotion Association CAS(2020015).
文摘Purpose Flexible waveguides,which allow for greater deformation as compared to traditional hard waveguides,are highly useful for simplifying waveguide system assemblies.However,the peak powers of these waveguides have been limited to several megawatts in non-vacuum environments.Herein,a novel flexible waveguide was developed for the S-band(2856 MHz)with the aim of facilitating the interconnection of two hard waveguides.Methods The flexible waveguide was composed of brass,and its surface was plated with oxygen-free high-conductivity copper for brazing with stainless steel flanges in a vacuum furnace.By connecting the stainless steel flanges together,it can be applied to a high-vacuum environment.Results The prototype exhibited good measurement results in low-power microwave tests;the results of a 72-h vacuum leak test showed satisfactory vacuum performance as well,and no obvious surface collapse was observed.High-power microwave commissioning was conducted between June and July 2019;the waveguide showed a maximum average power of approximately 2.7 kW.Conclusion Unfortunately,the prototype was damaged after reaching that power level,which indicates the need for further optimization of the fabrication process.From our experiment,it is clear that the flexible waveguide cannot be used in large accelerators because of its average power limit.
