In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency（LPRF） modulated frequency stepped frequency（MFSF） radar signal.The velocity range of the target is lar...In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency（LPRF） modulated frequency stepped frequency（MFSF） radar signal.The velocity range of the target is large and the velocity is high ambiguous,so the single method is difficult to satisfy the velocity measurement requirement.For this problem,a novel method is presented,it is a combination of cross-correlation inner frame velocity measurement and range-Doppler coupling velocity measurement.The cross-correlation inner frame method,overcoming the low Doppler tolerance of the cross-correlation between frames,can obtain the coarse velocity of the high speed target,and then the precision velocity can be obtained with the range-Doppler coupling method.The simulation results confirm the method is effective,and also it is well real-time and easy to the project application.展开更多
In the present paper we conduct a theoretical study of the thermal accumulation effect of a typical bipolar transistor caused by high power pulsed microwaves（HPMs）,and investigate the thermal accumulation effect as ...In the present paper we conduct a theoretical study of the thermal accumulation effect of a typical bipolar transistor caused by high power pulsed microwaves（HPMs）,and investigate the thermal accumulation effect as a function of pulse repetition frequency（PRF） and duty cycle.A study of the damage mechanism of the device is carried out from the variation analysis of the distribution of the electric field and the current density.The result shows that the accumulation temperature increases with PRF increasing and the threshold for the transistor is about 2 kHz.The response of the peak temperature induced by the injected single pulses indicates that the falling time is much longer than the rising time.Adopting the fitting method,the relationship between the peak temperature and the time during the rising edge and that between the peak temperature and the time during the falling edge are obtained.Moreover,the accumulation temperature decreases with duty cycle increasing for a certain mean power.展开更多
在医科达直线加速器运行过程中,程控脉冲信号发生器(Programmable Pulse Generator,PPG)PCB会发出脉冲重复频率(Pulse Repetition Frequency,PRF)ENABLE信号,依次经过3个控制区和多叶准直器以及直线加速器控制系统(Linac Control System...在医科达直线加速器运行过程中,程控脉冲信号发生器(Programmable Pulse Generator,PPG)PCB会发出脉冲重复频率(Pulse Repetition Frequency,PRF)ENABLE信号,依次经过3个控制区和多叶准直器以及直线加速器控制系统(Linac Control System,LCS)回到PPG PCB,如果各区域工作正常,则PPG PCB会向高压部分提供闸流管脉冲触发,脉冲成形网络会正常充放电,磁控管产生微波到加速管加速电子,加速器工作正常。如果PRF ENABLE信号经过的区域有工作异常的情况,则加速器不能正常出束。我院医科达直线加速器的临床使用过程中,多次出现PRF EN CHK连锁。本文总结我院医科达Synergy直线加速器运行过程中出现的PRF EN CHK连锁,详细分析了已出现故障或者可能发生的故障,重点介绍了排除故障的过程,供相关人员参考。展开更多
本文对高重频窄脉宽多波长激光器的可靠性进行了分析及验证,建立了高重频窄脉宽多波长激光器的框图法模型。在初始设计阶段开展激光器的可靠性分析,定量计算了激光器各单元的可靠性结果,包括失效率λ和平均无故障工作时间(Mean Time Bet...本文对高重频窄脉宽多波长激光器的可靠性进行了分析及验证,建立了高重频窄脉宽多波长激光器的框图法模型。在初始设计阶段开展激光器的可靠性分析,定量计算了激光器各单元的可靠性结果,包括失效率λ和平均无故障工作时间(Mean Time Between Failure,MTBF),预计激光器整机的无故障工作时间为1798.8 h。为满足激光器的设计指标要求,通过选用高品质晶体、半导体激光器的Ⅰ级降额设计和电源控制的冗余设计,实现激光器的可靠性优化。经优化设计后,激光器整机的无故障工作时间达2260.9 h。搭建激光器整机对可靠性优化设计结果进行验证,验证结果表明:激光器无故障工作时间可达2400 h。展开更多
文摘In the high speed target environment,there exists serious Doppler effect in the low pulse repetition frequency（LPRF） modulated frequency stepped frequency（MFSF） radar signal.The velocity range of the target is large and the velocity is high ambiguous,so the single method is difficult to satisfy the velocity measurement requirement.For this problem,a novel method is presented,it is a combination of cross-correlation inner frame velocity measurement and range-Doppler coupling velocity measurement.The cross-correlation inner frame method,overcoming the low Doppler tolerance of the cross-correlation between frames,can obtain the coarse velocity of the high speed target,and then the precision velocity can be obtained with the range-Doppler coupling method.The simulation results confirm the method is effective,and also it is well real-time and easy to the project application.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60776034)
文摘In the present paper we conduct a theoretical study of the thermal accumulation effect of a typical bipolar transistor caused by high power pulsed microwaves（HPMs）,and investigate the thermal accumulation effect as a function of pulse repetition frequency（PRF） and duty cycle.A study of the damage mechanism of the device is carried out from the variation analysis of the distribution of the electric field and the current density.The result shows that the accumulation temperature increases with PRF increasing and the threshold for the transistor is about 2 kHz.The response of the peak temperature induced by the injected single pulses indicates that the falling time is much longer than the rising time.Adopting the fitting method,the relationship between the peak temperature and the time during the rising edge and that between the peak temperature and the time during the falling edge are obtained.Moreover,the accumulation temperature decreases with duty cycle increasing for a certain mean power.
基金National Nature Science Foundation of China(Grant No.60972159,61032001)Aviation Science Foundation(Grant No.20085184003)Special Foundation Program for Mountain Tai Scholars of China
文摘在医科达直线加速器运行过程中,程控脉冲信号发生器(Programmable Pulse Generator,PPG)PCB会发出脉冲重复频率(Pulse Repetition Frequency,PRF)ENABLE信号,依次经过3个控制区和多叶准直器以及直线加速器控制系统(Linac Control System,LCS)回到PPG PCB,如果各区域工作正常,则PPG PCB会向高压部分提供闸流管脉冲触发,脉冲成形网络会正常充放电,磁控管产生微波到加速管加速电子,加速器工作正常。如果PRF ENABLE信号经过的区域有工作异常的情况,则加速器不能正常出束。我院医科达直线加速器的临床使用过程中,多次出现PRF EN CHK连锁。本文总结我院医科达Synergy直线加速器运行过程中出现的PRF EN CHK连锁,详细分析了已出现故障或者可能发生的故障,重点介绍了排除故障的过程,供相关人员参考。
文摘本文对高重频窄脉宽多波长激光器的可靠性进行了分析及验证,建立了高重频窄脉宽多波长激光器的框图法模型。在初始设计阶段开展激光器的可靠性分析,定量计算了激光器各单元的可靠性结果,包括失效率λ和平均无故障工作时间(Mean Time Between Failure,MTBF),预计激光器整机的无故障工作时间为1798.8 h。为满足激光器的设计指标要求,通过选用高品质晶体、半导体激光器的Ⅰ级降额设计和电源控制的冗余设计,实现激光器的可靠性优化。经优化设计后,激光器整机的无故障工作时间达2260.9 h。搭建激光器整机对可靠性优化设计结果进行验证,验证结果表明:激光器无故障工作时间可达2400 h。
