| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a helical antenna and in-vehicle antenna employing the same in which directivity is arbitrarily controlled within a limited mount range without increasing the size. Ž<P>SOLUTION: The helical antenna 10 includes a first helical portion 11 of which one turn corresponds to one wavelength and a second helical portion 12, of which one turn corresponds to two wavelengths, positioned radially outward of the first helical portion 11. Between an antenna beam radiated from the first helical portion 11 and an antenna beam radiated from the second helical portion 12, a difference occurs in phase and maximum gain direction. Thus, by changing a phase and a strength of high frequency power supplied to the first helical portion 11 and the second helical portion 12, directivity of a main beam formed from the antenna beams is controlled. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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