| 摘要 |
Arrays (12, 14), of helical antennas (16, 18), operate at spaced-apart frequencies. In order to reduce mutual coupling between the antenna elements (16) of the lower-frequency array (12), they are spaced apart by a gap equal to or greater than one wavelength. The lengths of the lower-frequency helices are adjusted to move nulls in their radiation patterns into congruence with unwanted peaks in the array pattern, thereby suppressing the grating lobes. In order to reduce the total area of the arrays (12 and 14), the arrays are interleaved with each other. The higher-frequency array (14) has its antenna elements (18) spaced apart by a larger number of wavelengths than that of the lower-frequency array (12), so reducing the mutual coupling even further. The number of turns of the helices of the high-frequency array (14) are adjusted to bring nulls in the radiation pattern of the individual antennae (18) into coincidence with unwanted grating lobes. <IMAGE>
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