阐述数字幅度调制(Digital Amplitude Modulation,DAM)中波发射机模数(Analog to Digital,A/D)转换原理、A/D转换板主要组成部分及其作用,列举A/D转换板在实际运行中出现的常见故障案例,对常见故障给出分析和处理方法,为今后该板的故障...阐述数字幅度调制(Digital Amplitude Modulation,DAM)中波发射机模数(Analog to Digital,A/D)转换原理、A/D转换板主要组成部分及其作用,列举A/D转换板在实际运行中出现的常见故障案例,对常见故障给出分析和处理方法,为今后该板的故障分析和处理工作提供参考。展开更多
Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and p...Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.展开更多
Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In or...Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In order to improve the phase-coding modulation rate, we proposed a new digital-modulation method in this paper and constructed a compact and robust prototype of QKD system using currently available components in our lab to demonstrate the effectiveness of the method. The system was deployed in laboratory environment over a 50 km fiber and continuously operated during 87 h without manual interaction. The quantum bit error rate （QBER） of the system was stable with an average value of 3.22% and the secure key generation rate is 8.91 kbps. Although the modulation rate of the photon in the derno system was only 200 MHz, which was limited by the Faraday- Michelson interferometer （FMI） structure, the proposed method and the field programmable gate array （FPGA） based electronics scheme have a great potential for high speed QKD systems with Giga-bits/second modulation rate.展开更多
With regard to problems in conventional synthetic aperture radar （SAR）, such as imaging distortion, beam limitation and failure in acquiring three-dimensional （3-D） information, a downward-looking 3-D imaging meth...With regard to problems in conventional synthetic aperture radar （SAR）, such as imaging distortion, beam limitation and failure in acquiring three-dimensional （3-D） information, a downward-looking 3-D imaging method based on frequency modulated continuous wave （FMCW） and digital beamforming （DBF） technology for airborne SAR is presented in this study. Downward-looking 3-D SAR signal model is established first, followed by introduction of virtual antenna optimization factor and discussion of equivalent-phase-center compensation. Then, compensation method is provided according to reside video phase （RVP） and slope term for FMCW SAR. As multiple receiving antennas are applied to downward-looking 3-D imaging SAR, range cell migration correction （RCMC） turns to be more complex, and corrective measures are proposed. In addition, DBF technology is applied in realizing cross-track resolution. Finally, to validate the proposed method, magnitude of slice, peak sidelobe ratio （PSLR）, integrated sidelobe ratio （ISLR） and two-dimensional （2-D） contour plot of impulse response function （IRF） of point target in three dimensions are demonstrated. Satisfactory performances are shown by simulation results.展开更多
文摘阐述数字幅度调制(Digital Amplitude Modulation,DAM)中波发射机模数(Analog to Digital,A/D)转换原理、A/D转换板主要组成部分及其作用,列举A/D转换板在实际运行中出现的常见故障案例,对常见故障给出分析和处理方法,为今后该板的故障分析和处理工作提供参考。
基金supported by the National Natural Science Foundation of China(Grant Nos.62101258,62071235 and 62271260)the Jiangsu Province Science&Technology Department(Grant No.BE2021017).
文摘Time-modulated array(TMA)antennas,introduce the dimension of time into antenna design to control the radiation patterns and frequency spectral characteristics,thus improve the reconfigurability of array antennas and provide multiple functional-ities.They have great application potential in military and civilian fields,such as precision guidance and mobile communication,and are currently a hot spot of academic research.This article provides a review on the fundamentals and applications of TMAs.First,the basic theory and mathematical formulations of TMAs are introduced.Second,the most important applications of TMAs,namely time-modulated phased arrays(TMPA),are discussed from the perspectives of harmonic suppression and harmonic utiliza-tion,which are used for single-beam and multibeam radiation.Then,we survey the combination of TMA with various types of novel antenna arrays,such as single-channel digital beamforming(DBF)arrays,frequency diverse arrays(FDAs),and retrodirective arrays,to create new hardware implementation methods and enhance their performance.Next,recent advances in dedicated integrated chips for TMA,which have played a significant role in driving the progress of TMAs from academic research to practical applications,are presented.Finally,the challenges and prospects for TMAs are discussed,including new research directions and emerging applica-tion scenarios.
基金supported by the National Key Basic Research Program of China(Grant Nos.2011CBA00200 and 2011CB921200)the National Natural Science Foundation of China(Grant Nos.61201239,6120511811304397 and 61475148)the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDB01030100 and XDB01030300)
文摘Quantum key distribution （QKD） is a technology with the potential capability to achieve information-theoretic security. Phase- coding is an important approach to develop practical QKD systems in fiber channel. In order to improve the phase-coding modulation rate, we proposed a new digital-modulation method in this paper and constructed a compact and robust prototype of QKD system using currently available components in our lab to demonstrate the effectiveness of the method. The system was deployed in laboratory environment over a 50 km fiber and continuously operated during 87 h without manual interaction. The quantum bit error rate （QBER） of the system was stable with an average value of 3.22% and the secure key generation rate is 8.91 kbps. Although the modulation rate of the photon in the derno system was only 200 MHz, which was limited by the Faraday- Michelson interferometer （FMI） structure, the proposed method and the field programmable gate array （FPGA） based electronics scheme have a great potential for high speed QKD systems with Giga-bits/second modulation rate.
文摘With regard to problems in conventional synthetic aperture radar （SAR）, such as imaging distortion, beam limitation and failure in acquiring three-dimensional （3-D） information, a downward-looking 3-D imaging method based on frequency modulated continuous wave （FMCW） and digital beamforming （DBF） technology for airborne SAR is presented in this study. Downward-looking 3-D SAR signal model is established first, followed by introduction of virtual antenna optimization factor and discussion of equivalent-phase-center compensation. Then, compensation method is provided according to reside video phase （RVP） and slope term for FMCW SAR. As multiple receiving antennas are applied to downward-looking 3-D imaging SAR, range cell migration correction （RCMC） turns to be more complex, and corrective measures are proposed. In addition, DBF technology is applied in realizing cross-track resolution. Finally, to validate the proposed method, magnitude of slice, peak sidelobe ratio （PSLR）, integrated sidelobe ratio （ISLR） and two-dimensional （2-D） contour plot of impulse response function （IRF） of point target in three dimensions are demonstrated. Satisfactory performances are shown by simulation results.
