| 摘要 |
Provided are an array antenna capable of miniaturizing an array antenna while reducing side lobes, a tag communication device and tag communication system provided with the array antenna, and a beam control method for the array antenna. When XY coordinates and a feeding phase of each antenna element (21a to 21d) are defined as the antenna element (21a) (0, Y1)·&phgr;1, the antenna element (21b) (−X1, 0)·&phgr;2, the antenna element (21c) (X2, 0)·&phgr;3, the antenna element (21d) (0, −Y2)·&phgr;4, wavelengths of λ, and directivity directions of &thetas;, each of the feeding phases is set so that the following conditional equations &phgr;1=&phgr;4, &phgr;2=2&pgr;·X1·sin(&thetas;)/λ+&phgr;1, &phgr;3=&phgr;1−2&pgr;·X2·sin(&thetas;)/λ are all satisfied.
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