| 摘要 |
<P>PROBLEM TO BE SOLVED: To enable a radio tag to receive a radio wave regardless of the arrangement direction of the radio tag when causing leakage electric field and communicating with the radio tag which is placed above with some space from the generated electric field. <P>SOLUTION: An antenna device comprises: a first conductor layer; a second conductor layer which is placed above and substantially parallelly spaced from the first conductor layer, and causes an electromagnetic wave travelling parallel with a first axis; and a first conductor part which is a prescribed area provided in the second conductor layer or separately on the second conductor layer. The second conductor layer is provided with a non-conductor portion partly; thereby causing leakage electric field in upper space. A first length where a second axis overlaps with the prescribed area of the first conductor part is set to a length by which reception power of the radio tag is at or above a first reference value when a prescribed radio tag is placed at a prescribed hight from the first conductor part and in parallel to the first axis, the second axis and a third axis perpendicular to the plane of the second conductor layer, respectively. <P>COPYRIGHT: (C)2012,JPO&INPIT |
