Magnetantenne

摘要

1,058,812. Aerials. SIYMITOMO ELECTRIC INDUSTRIES Ltd. June 17, 1964 [June 21, 1963 (4)], No. 25136/64. Heading H4A. In a magnetic aerial an active element 2, Fig. 3 (not shown), of helical form is placed near and parallel to a conducting sheet 1 in which an image is formed whose electric component I' is opposed to the electric component I of the helix 2, but whose magnetic component M1 reinforces the magnetic component M of the helix 2. It is stated that the electric components cancel out and that the magnetic components only are effective in producing electromagnetic radiation. Alternatively, two adjacent helices may be used, Fig. 4 (not shown), in which the second helix simulates an image of the first, i.e. it is wound in the opposite sense and the current in it is the same as in the first helix, but is reversed. In a first embodiment, Fig. 5, two vertical centre-fed helices 2, 3 are placed in proximity to and on opposite sides of a conducting plate 1 and provide a doughnut-shaped radiation pattern, with horizontal polarization. In a second embodiment, Fig. 6 (not shown), two vertical centre-fed helices are placed on each side of a conducting plate. Various horizontal radiation patterns may be obtained by altering the distance between the axes of each pair of helices, and the relative phases of the exciting currents. In a third embodiment, Fig. 7, a number of similar helices 2, 3, 4, 5 each of axial length #e/2, where #e is the axial length of a helix corresponding to one wavelength, are connected by straight conductors each of length #/2, where # is substantially the free space wavelength. The assembly, which is centre-fed, is placed in proximity to a conducting plate 1 and is equivalent to a magnetic aerial comprising a plurality of colinear inphase elements. In a fourth embodiment, Fig. 8 (not shown), the straight conductor portions are omitted, but adjacent helices are wound in opposite senses. In a fifth embodiment, Fig. 9 (not shown), each of four vertical helices is placed in a corner formed by two vertical conducting plates intersecting at right-angles. When the helices are excited in phase a radiation pattern which is omnidirectional in horizontal planes is obtained, but this may be altered by varying the relative phases of the feeds to the helices. In a sixth embodiment, Fig. 10, a helix is formed into a ring and placed in proximity to a horizontal conducting plate. The radiation pattern is of semi-doughnut pattern, with vertical polarization, as with a unipole aerial. In a seventh embodiment, Fig. 13 (not shown), a helix formed into a ring comprises several sections as in the third or fourth embodiments, for the purpose of changing the shape of the radiation pattern from that obtained with the sixth embodiment. In an eighth embodiment, Fig. 14, two helices 2 are themselves wound helically, in opposite directions, upon a metal cylinder 1 with their terminals FP 1 and FP 2 adjacent, the length of a turn being made an integral multiple of #e. When terminals FP 1 , FP 2 are excited in antiphase, a vertical resultant magnetic vector ensues, giving horizontally polarized radiation, Figs. 15, 16a (not shown). When the terminals are excited in phase, a horizontal magnetic vector ensues, giving vertically polarized radiation, Fig. 16b (not shown). If the helix angles are Œ45 degrees and the terminals FP 1 , FP 2 are excited with 90 degrees phase difference, circularly polarized radiation may be obtained.