| 摘要 |
PROBLEM TO BE SOLVED: To measure the arrival direction of electromagnetic waves accurately and speedily even in the case of low frequencies. SOLUTION: Scanning is performed by an antanna 11 of a directional rotating beam, and a beam waveform including the acquisition results of acquired electromagnetic waves is converted into an intermediate frequency and then converted into a direction finding signal waveform which indicates a maximum amplitude at the arrival direction of the electromagnetic waves at a direction finding waveform shaping part 13. The direction signal waveform is sampled at approximate cycles at an A/D converting part 14 and supplied for a first correlation processing part 18. In the first correlation processing part 18, with reference to a first reference waveform (16), the components of waveform changes in a unit of time are extracted and combined to create a first impulse response waveform which indicates a maximum peak value at the arrival direction. In a second correlation processing part 21, the azimuth direction is further limited (ϕ) with the arrival direction as a center to create a second impulse response waveform. As the impulse response waveform that indicates the arrival direction of electromagnetic waves is created by two stages in this way, it is possible to measure the arrival direction speedily and highly accurately.
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