星用成形放大器

设计一个卫星上辐射测量系统中的成形脉冲放大器。成形方法采用准高斯成形方法,成形时间常数为1.6μs。放大器采用多级负反馈放大器结构形式,总放大倍数约4000倍。器件采用低功耗集成运算放大器。总的功率为16mW,质量约为20g。     

高温磁悬浮轴承用位移传感器的研究简

 针对差动变压器式位移传感器的性能及其在高温磁悬浮轴承中的应用,对环境温度升高影响差动变压器式位移传感器（DTDS）性能的机理和特征以及所采用的温度补偿技术进行了研究。采用比值方式的处理电路以及加入补偿电阻的方法改善了温度升高所带来位移传感器灵敏度升高、温度漂移和时间漂移的问题。对不同温度下的差动变压器式位移传感器进行标定得到了位移传感器的动静态性能,并将其应用到单自由度高温磁悬浮轴承（HTAMB）试验台上进行静态和模拟动态悬浮。研究结果表明,环境温度为550 ℃,被测物体移动范围在-0.35~+0.35 mm时,位移传感器的灵敏度在19.62 mV/μm,线性度为±0.74%,迟滞性为±0.40%,重复性为±0.97%,传感器截止频率在800 Hz左右;在单自由度高温磁悬浮轴承试验台上使用所研制的高温位移传感器,能实现被悬浮物体的稳定悬浮。     

线形调频DDS及其误差分析

采用ＤＤＳ技术产生线形调频（ｃｈｉｒｐ）信号是一种简单有效的方法，与其他方法相比，这种方法易于实现波形捷变，易于实现调频带较宽的ｃｈｉｒｐ信号。然而产生过程引入了相位误差和幅度误差。这些误差将对脉冲压缩结果造成影响，在系统设计中必须设法控制。本文在分析用ＤＤＳ实现ｃｈｉｒｐ信号的原理的基础上，给出了ｃｈｉｒｐ信号的ＤＤＳ产生方案，该方法不用修改通用ＤＤＳ的结构，便可实现各种参数ｃｈｉｒｐ信号的产生。文中对误差进行了分析，给出工程实现上参数选取的依据。并讨论了这些误差对脉压系统性能的影响。     

基于旋转阀的脉冲爆震火箭发动机实验

针对现有条件下电磁阀高频与大流量不可兼得的矛盾,设计了一种凸轮式旋转阀,以此来控制脉冲爆震火箭发动机氧化剂、燃料和隔离气体的间歇式供给.基于该旋转阀,以汽油和富氧空气为推进剂,进行了不同频率下的实验.实验结果表明,推进剂和隔离气供给压力与点火相位直接影响到能否稳定起爆.随着频率的增加,在1～ 10 Hz范围内,降低隔离氮气压力、调整点火相位可实现发动机的稳定工作;10Hz以上时,仅需要提高油气的供给压力.基于该旋转阀控制技术,脉冲爆震火箭发动机实现了工作频率30 Hz的稳定工作.     

点火能量对脉冲爆震发动机性能的影响

针对以汽油-空气为推进剂的吸气式脉冲爆震发动机,研究了点火能量及工作频率对发动机点火-起爆时间和发动机推进性能的影响。结果显示,随着点火能量的提高,点火-起爆时间逐渐减小,脉冲爆震发动机平均推力逐渐增加。随着发动机工作频率的提高,点火-起爆时间也逐渐减小,发动机稳定工作的最佳油气当量比减小,发动机平均推力接近线性增加;但是点火能量对发动机点火-起爆时间的影响随着工作频率的提高而有所降低。     

脉冲燃烧风洞点式油流技术在压缩拐角流动显示中的应用

为在脉冲燃烧风洞上应用油流技术,针对该类设备马赫数6条件下气流总温高(可达1650K)、有效试验时间短(约300ms)、小动压条件下显示油"流不动"等困难,提供了一种技术解决方案。试验设备为中国空气动力研究与发展中心Φ=600mm脉冲燃烧风洞。采用两个多级压缩楔模拟高超进气道外压缩面,其中三级压缩楔偏转角为6°,7°和8°,两级压缩楔偏转角均为10°。运用高速摄像方法获得了点式图谱的动态变化过程。三级压缩楔8°拐角上游油点在200ms内流过了拐角,并向下游移动了足够长度,可判断该拐角处气流不产生分离。两级压缩楔油流结果则显示风洞尾气会显著改变图谱分布。     

Thrust measurement method verification and analytical studies on a liquid-fueled pulse detonation engine

In order to test the feasibility of a new thrust stand system based on impulse thrust mea- surement method, a liquid-fueled pulse detonation engine （PDE） is designed and built. Thrust per- formance of the engine is obtained by direct thrust measurement with a force transducer and indirect thrust measurement with an eddy current displacement sensor （ECDS）. These two sets of thrust data are compared with each other to verify the accuracy of the thrust performance. Then thrust data measured by the new thrust stand system are compared with the verified thrust data to test its feasibility. The results indicate that thrust data from the force transducer and ECDS system are consistent with each other within the range of measurement error. Though the thrust data from the impulse thrust measurement system is a litter lower than that from the force transducer due to the axial momentum losses of the detonation jet, the impulse thrust measurement method is valid when applied to measure the averaged thrust of PDE. Analytical models of PDE are also discussed in this paper. The analytical thrust performance is higher than the experimental data due to ignoring the losses during the deflagration to detonation transition process. Effect of equivalence ratio on the engine thrust performance is investigated by utilizing the modified analytical model. Thrust reaches maximum at the equivalence ratio of about 1.1.     

脉冲干扰对软件接收机的影响分析

卫星信号经过长距离传播,信号能量损耗严重,到达地面的功率很弱,容易受到各种干扰的影响。脉冲干扰为常见的干扰类型,所以针对不同功率、不同周期,以及不同占空比的脉冲干扰信号,通过接收前端采集受脉冲干扰的GPS L1信号,利用软件接收机及多相关器生成技术,详细分析了脉冲干扰对接收机信号捕获与跟踪性能的影响。分析结果表明,周期为1ms的脉冲干扰信号,能对接收机产生强烈的干扰效果,捕获图中的噪声明显增大;跟踪过程中,载噪比和相关值突发性减小,造成跟踪数据异常。而长周期的脉冲信号仅在脉冲到达时影响接收机的捕获和跟踪,但由于信号跟踪不能连续进行,导致伪距观测量的不连续与导航数据不能正常解码,从而干扰接收机。     

Fast approximate maximum likelihood period estimation from incomplete timing data

 To estimate the period of a periodic point process from noisy and incomplete observations, the classical periodogram algorithm is modified. The original periodogram algorithm yields an estimate by performing grid search of the peak of a spectrum, which is equivalent to the periodogram of the periodic point process, thus its performance is found to be sensitive to the chosen grid spacing. This paper derives a novel grid spacing formula, after finding a lower bound of the width of the spectral mainlobe. By employing this formula, the proposed new estimator can determine an appropriate grid spacing adaptively, and is able to yield approximate maximum likelihood estimate (MLE) with a computational complexity of O(n²). Experimental results prove that the proposed estimator can achieve better trade-off between statistical accuracy and complexity, as compared to existing methods. Simulations also show that the derived grid spacing formula is also applicable to other estimators that operate similarly by grid search.     

隔舱式双脉冲发动机金属膜片设计与实验研究

为得到双脉冲发动机隔舱结构关键部件金属膜片适宜结构,通过圆板大挠度理论和断裂力学理论推导出金属膜片预制缺陷处应力强度因子计算公式,得到金属膜片在内压作用下的设计方法,建立了膜片破坏压强与结构尺寸之间定量关系,并通过6次膜片动态破坏单项实验验证了其正确性.在此基础上,利用缩比发动机分别开展了隔舱热流承压、热流打开、热流联合实验以进一步考核隔舱的工作特性.结果表明:所导出的金属膜片设计方法与实验结果较为一致,平均误差约4.394％,可以用于脉冲发动机膜片具体结构尺寸设计;隔舱承压、密封、打开、消融性能良好,可以较好满足双脉冲发动机使用要求.