Development of Electromagnetic Noise Source Searching System Using Synthetic Aperture Method

电磁噪声源搜索系统由四个子系统组成：(1)天线子系统：九个偶极子天线。包括一个标准天线。(2)通道选择子系统：8输入/1输出同轴开关系统。(3)幅相测量子系统：对接收信号进行相位测量。通过一个标准的天线。并通过矢量伏特计为每个天线预留幅度。(4)系统控制子系统：整个系统控制。数据收集。和前置处理。各子系统之间通过接口连接。我完全是我们自己的作品。通过系统控制分系统实现数据的自动测量，并开发了自动测量和数据处理软件。(1)系统控制软件。(2)记录数据预解析软件。(3)工程工作站数据转换成数据处理系统的软件。(4)数据处理与显示软件。(5)数值模拟软件。采用米尔斯交叉法的电磁噪声搜索系统。可应用于菲涅尔区。该系统仅限于合成孔径的十倍波长。所以。菲涅尔区是孔径中心波长的200倍。在我们的实验中。场被限制为100倍波长，每个x轴安迪轴上10倍波长的区域在100倍波长平方的区域内四处移动。该系统通过数值模拟对波源进行了估计。该系统可以估计100倍波长平方以下的波源。并利用波源估计的估计函数对阵列天线的精度进行了估计。结果表明，对交叉角的精度要求很高。交叉角的误差需要+-1度才能在每一轴上10倍波长范围内的任何地方保持相同的精度。

The electromagnetic noise sources searching system is composed of four sub-systems.(1) Antenna sub-system : nine dipole antennae. including a standard antenna.(2) Channel selector sub-system : eight input/one output coaxial switchig system(3) Amplitude and phase measuring sub-system : measuring phase to received signal. by a standard antenna. and reserved amplitude for each antenna by a vector-volt meter.(4) System control sub-syste : Whole system control. data collection. and preprocessing. Each sub-systems were connected by interfaces. whichi were our own work completely. Data was measured automatically by systemeontrol sub-systeolSoftware has been developed for automatic measurement and data processing. (1) software for system control. (2) software for pre-proseccing of recorded data. (3) software for data convert to data proseecing system on an engineering workstation. (4) software for data processing and display representation. (5) software for numerical simulation.Electromagnetic noise search system which uses Mills' Cross Method. can be applied to Fresnel region. The system is restricted only ten times wavelength of synthetic aperture. So. Fresnel region is 200 times of wavelength rfom center of aperture. In our experiment. the field was restricted 100 times of wavelength and the region of 10 times of wavelength in each x-axis andy-axis was moved everywhere in the region of 100 times of wavelength square. The system estimated the wave source using numerical simulation. The system could estimate the wave source under 100 times of wavelength square. We also estimated the accuracy of array antenna using estimation function of wave source estimation. The results was that the requirement for the accuracy of crossing angle was very rigid. The error of the crossing angle required +-1 degree to keep the same accuracy everywhere in the region of 10 times of wavelength in each axis.