Development of Electromagnetic Noise Source Searching System Using Synthetic Aperture Method

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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.