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本文描绘了测量由羽流引起的雷达衰减和噪声的新设备。介绍了三种固体推进发动机点火试验,报告了X波段衰减,幅度噪声和相位噪声的测量。显示了边带频率和羽流位置对于噪声电平的影响。对高浸镀铝推进燃料来说峰值衰减大约为12～15db。跟衰减一样,最大噪声电平发生在羽流的二次燃烧区域且强烈地依赖于羽流的位置。接近喷嘴出口平面,500H_z带宽内,偏离载频1KH_zX波段载波幅度噪声大约为37dbc。在羽流的尾部区域,衰减和幅度噪声电平分别增加大约3和10db。相位噪声电平与幅度噪声电平相匹敌。这种测试装置的结果和以前几乎相同的推进/发动机系统报告数据进行了比较。衰减和幅度噪声的测量和早期测试的相吻合,但是相位噪声的测量比以前的报告要高。由于对设备进行认真的校准并消除了声频噪声,因此这些新的数据是比较准确的。
This article describes a new device that measures radar attenuation and noise caused by plumes. Three kinds of solid propellant engine ignition tests are introduced, and the measurement of X-band attenuation, amplitude noise and phase noise are reported. The effect of sideband frequency and plume position on the noise level is shown. The peak decay is about 12 ~ 15db for high-dipping aluminum propulsion fuels. As with attenuation, the maximum noise level occurs in the secondary combustion zone of the plume and strongly depends on the plume’s position. Close to the nozzle exit plane, 500H_z bandwidth, deviation from carrier frequency 1KH_zX band carrier amplitude noise is about 37dbc. At the tail of the plume, the attenuation and amplitude noise levels increase by about 3 and 10 dB, respectively. The phase noise level rivals the amplitude noise level. The results of this test set are compared with the prophase / engine system reporting data that was previously nearly the same. The attenuation and amplitude noise measurements coincide with earlier tests, but the phase noise measurements are higher than previously reported. These new data are more accurate due to the careful calibration of the equipment and the elimination of audible noise.