应答式目标旋转运动对雷达速度测量的影响

携带应答机的飞行目标,若除了沿其某一轨道运动外,还作自旋运动,应答机天线辐射相位空间分布的不均匀性会使应答机转发信号产生附加的相位调制,因而导致多卜勒测量雷达的测量误差。本文分析了对称安装三天线园柱形应答式目标回波的多卜勒频率调制。得出了附加多卜勒频率及其各阶导数的解析式。研究了目标旋转速度、方向角(目标旋转轴线与雷达视线的夹角)和回波谱线宽度的关系,以及对雷达多卜勒测量精度的影响,它对于研究自旋再入体测量问题具有实用价值。文章给出了一个典型的三天线园锥目标模拟旋转试验结果。试验中在不同目标转速下由相参雷达跟踪测量目标回波,同时记录中频信号、多卜勒跟踪回路鉴频器输出等有用信息。对试验数据的分析得出了明确的结论:目标旋转使回波信号的谱线展宽、测速误差增大,谱线宽度与目标转速成正比,同时谱线宽度随目标方向角增大而加宽,方向角为90°时旋转影响最大。理论分析得出了与试验相同的结果。虽然试验是在静态下进行的,但问题的分析对质心运动的目标也同样适用。

THE EFFECT OF THE SELF-ROTATION OF THE TARGET WITH A TRANSPONDER ON THE RADAR VELOCITY MEASUREMENT

For the target flying in the spacw, if it not only moves along a certain orbit but self-rotates, the additional phase-modulation will appear in the signal replied by the coherent transponder because the phase distribution of the signal radiated by the transponder antenna system is not uniform. In the result, an additional error in the Doppler measurement will be brought about. In this paper, an additional Doppler frequency in such signal is analysed, that signal is replied by the coherent transponder carried by the metal cylinder with three antennas mounted symmetricaly. The analytic representation of the additional Doppler frequency and its derivatives are presented in the paper. The effect of the rotation rate and the aspect angle of the target, which is defined as the angle between the rotation axis of the target and the radar line of sight, on the width of the echo spectral fine line and the measurement accuracy of the Doppler data are discussed. The obtained conclusions are very useful in practice. In the paper, the conditions and the result of a simulation test on the rotation of the target which is typical metal circular cone with three element antennas are also given. For different rotation rate of the target, the signal replied by the transponder is received and measured by a coherent radar in the test. At a time, the intermediate frequency signal at the input of the Doppler tracker and the output of the frequency discriminator in the Doppler tracker are recorded. We have obtained a conclusion as follows. Because the effect of the target rotation spreads the spectral fine line the measurement error of the target velocitynincreases,the width of the spectral fine line is proportional to the rotation rate and is spreaded with the target aspect angle increasing. The effect of the target rotation on Doppler measurement is the most severe when the target aspest angle is equal to 90 degrees. The above-mentioned conclusion is identical with the result of theoretical analysis in the paper. The paper emphasizes that the conclusion drawn is suitable to the target, the mass center of which is motive although the simulation test is performed in the static state conditions in which the mass center of the target is not motive.