针对航天光学遥感成像系统输出通道多、输出速率高的特点,提出一种高速、多通道CCD图像数据并行处理与传输系统的设计方案。该方案以FPGA为数据处理和控制核心,采用基于FPGA区域并行处理的数据处理方法,运用FPGA内部块RAM构建高速多通道...针对航天光学遥感成像系统输出通道多、输出速率高的特点,提出一种高速、多通道CCD图像数据并行处理与传输系统的设计方案。该方案以FPGA为数据处理和控制核心,采用基于FPGA区域并行处理的数据处理方法,运用FPGA内部块RAM构建高速多通道CCD图像的缓冲区,在存取控制上采取区域缓存和时分复用的策略完成对高速多通道CCD图像数据的实时处理;而对高速多通道CCD图像数据的传输采用基于Channel link高速差分串行传输技术,以高速差分串行的LVDS(Low Voltage Differential Signal)数据流替代传统的并行"TTL/COMS"信号进行传输,使系统高速传输能力大大加强,并且功耗低,抗干扰能力强。研究结果表明,该设计具有较好的稳定性、灵活性和通用性等,并已成功运用于某40通道高速CCD成像系统中,系统并行处理和传输的总数据率高达7.68Gbit/s。展开更多
设计实现了一种带参考通道的时间交叉ADC(TIADC)通道误差数字后台实时校准方法。参考通道ADC与TIADC各个子通道ADC依次对齐,对同一输入信号在同一时刻进行采样并转换,输出差值被用在数字后台LMS自适应校准算法中以计算通道间的失配误差...设计实现了一种带参考通道的时间交叉ADC(TIADC)通道误差数字后台实时校准方法。参考通道ADC与TIADC各个子通道ADC依次对齐,对同一输入信号在同一时刻进行采样并转换,输出差值被用在数字后台LMS自适应校准算法中以计算通道间的失配误差估计值,实现对各通道失调失配、增益失配和采样时刻失配造成误差的实时校准。FPGA实验结果表明,应用于12 bit,4通道,采样频率400 MS/s的TIADC中,归一化输入频率fin/fs=0.134时,在失调误差、增益误差和采样时钟误差分别为5%FSR、5%和1%Ts条件下,校准后信号噪声失真比(SNR)和无杂散动态范围(SFDR)分别提高了约19.61 d B和28.28 d B,为73.83 d B和86.15 d B,有效位达到11.96位。本校准方法计算复杂度低、易于硬件实现,能够应用于任意通道数的TIADC校准。展开更多
The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is prop...The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.展开更多
Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless commu...Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.展开更多
A comparison is made of the high-speed （2000 fps） lightning between two techniques. The analysis shows （UPL） in altitude-triggered negative lightning （ATNL） photographic records in rocket-triggered negative that...A comparison is made of the high-speed （2000 fps） lightning between two techniques. The analysis shows （UPL） in altitude-triggered negative lightning （ATNL） photographic records in rocket-triggered negative that： the initial speed of upward positive leader is about one order of magnitude less than that in classically triggered negative lightning （CTNL）, while the triggering height of ATNL is higher than that of CTNL; the afterglow time of metal-vaporized part of the lightning channel can endure for about 160-170 ms, thus the luminosity of the air-ionized part can reflect the characteristics of the current in the lightning channel better than that of the metal-vaporized part. According to the different characteristics of the luminosity change of the lightning channel, together with the observation of the electric field changes, three kinds of processes after return-stroke （RS） can be distinguished： the continuous decaying type without M component, the isolated type and the continuing type with M component, corresponding to different wave shapes of the continuous current. The geometric mean of the interval of RS with M component is 77 ms, longer than that （37 ms） of RS without M component. And the initial continuous current （ICC） with M component also has a longer duration compared to the ICC without M component. The distinction in the relative luminosity between the lightning channel before RS and that before M component is obvious： the former is very weak or even cannot be observed, while the latter is still considerably luminous.展开更多
文摘针对航天光学遥感成像系统输出通道多、输出速率高的特点,提出一种高速、多通道CCD图像数据并行处理与传输系统的设计方案。该方案以FPGA为数据处理和控制核心,采用基于FPGA区域并行处理的数据处理方法,运用FPGA内部块RAM构建高速多通道CCD图像的缓冲区,在存取控制上采取区域缓存和时分复用的策略完成对高速多通道CCD图像数据的实时处理;而对高速多通道CCD图像数据的传输采用基于Channel link高速差分串行传输技术,以高速差分串行的LVDS(Low Voltage Differential Signal)数据流替代传统的并行"TTL/COMS"信号进行传输,使系统高速传输能力大大加强,并且功耗低,抗干扰能力强。研究结果表明,该设计具有较好的稳定性、灵活性和通用性等,并已成功运用于某40通道高速CCD成像系统中,系统并行处理和传输的总数据率高达7.68Gbit/s。
文摘设计实现了一种带参考通道的时间交叉ADC(TIADC)通道误差数字后台实时校准方法。参考通道ADC与TIADC各个子通道ADC依次对齐,对同一输入信号在同一时刻进行采样并转换,输出差值被用在数字后台LMS自适应校准算法中以计算通道间的失配误差估计值,实现对各通道失调失配、增益失配和采样时刻失配造成误差的实时校准。FPGA实验结果表明,应用于12 bit,4通道,采样频率400 MS/s的TIADC中,归一化输入频率fin/fs=0.134时,在失调误差、增益误差和采样时钟误差分别为5%FSR、5%和1%Ts条件下,校准后信号噪声失真比(SNR)和无杂散动态范围(SFDR)分别提高了约19.61 d B和28.28 d B,为73.83 d B和86.15 d B,有效位达到11.96位。本校准方法计算复杂度低、易于硬件实现,能够应用于任意通道数的TIADC校准。
基金supported by the China Major State Basic Research Development Program(973 Program,No.2012CB316100)National Natural Science Foundation of China(No.61171064)+2 种基金the China National Science and Technology Major Project(No.2010ZX03003-003)NSFC(No.61021001)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(No.2011D13)
文摘The challenges of severe Doppler effects in high-speed railway are considered. By building a cooperative antenna system; an algorithm of joint channel estimation and Doppler frequency offset （DFO） estimation is proposed based on Ricean channel model. First, a maximum likelihood estimation （MLE） algorithm for DFO is designed, show- ing that the Doppler estimation can be obtained by estimating moving velocity of the train and the path loss with the exploitation of pilots that are placed inside the frame. Then a joint detection algorithm for the receiver is proposed to exploit multi-antenna diversity gains. Last, the theoretical Crammer Rao bound （CRB） for joint channel estimation and DFO estimation is derived. The steady performance of the system is confirmed by numerical simulations. In particular, when the Ricean fading channel parameter equals 5 and the velocities of train are 100 m/s and 150 m/s, the estimation variances of DFO are very close to the theoretical results obtained by using CRB. Meanwhile, the corresponding sig- nal to noise ratio loss is less than 1.5 dB when the bit error rate is 10-5 for 16QAM signals.
基金supported in part by the National Natural Science Foundations(Nos.61032002 and 61102050)the National Science and Technology Major Project(No.2011ZX03001-007-01)+1 种基金the Beijing Natural Science Foundation(No.4122061)the Fundamental Research Funds for the Central Universities(No.2012YJS005)
文摘Wireless communication for high-speed railways （HSRs） that provides reliable and high data rate communi- cation between the train and trackside networks is a challenging task. It is estimated that the wireless communication traffic could be as high as 65 Mbps per high-speed train. The development of such HSR communications systems and standards requires, in turn, accurate models for the HSR propagation channel. This article provides an overview of ex- isting HSR channel measurement campaigns in recent years. Particularly, some important measurement and modeling results in various HSR scenarios, such as viaduct and U-shaped groove （USG）, are briefly described and analyzed. In addition, we review a novel channel sounding method, which can highly improve the measurement efficiency in HSR environment.
基金the National Natural Science Foundation of China under Grant No.40605004the Ministry of Science and Technology of China under Grant Nos.2004DEA71070 and GYHY2007622
文摘A comparison is made of the high-speed （2000 fps） lightning between two techniques. The analysis shows （UPL） in altitude-triggered negative lightning （ATNL） photographic records in rocket-triggered negative that： the initial speed of upward positive leader is about one order of magnitude less than that in classically triggered negative lightning （CTNL）, while the triggering height of ATNL is higher than that of CTNL; the afterglow time of metal-vaporized part of the lightning channel can endure for about 160-170 ms, thus the luminosity of the air-ionized part can reflect the characteristics of the current in the lightning channel better than that of the metal-vaporized part. According to the different characteristics of the luminosity change of the lightning channel, together with the observation of the electric field changes, three kinds of processes after return-stroke （RS） can be distinguished： the continuous decaying type without M component, the isolated type and the continuing type with M component, corresponding to different wave shapes of the continuous current. The geometric mean of the interval of RS with M component is 77 ms, longer than that （37 ms） of RS without M component. And the initial continuous current （ICC） with M component also has a longer duration compared to the ICC without M component. The distinction in the relative luminosity between the lightning channel before RS and that before M component is obvious： the former is very weak or even cannot be observed, while the latter is still considerably luminous.
