Patent ID: 9000992
Filing Date: 2015-04-07
Classification: H01Q

Abstract:
1. An antenna device for transmitting a radio wave to a tag capable of receiving the radio wave, the antenna device comprising: a first layer which is electrically conductive; a second layer disposed parallel to the first layer and apart from the first layer and being electrically conductive so as to generate an electromagnetic wave travelling along a first axis, the second layer including a plurality of portions that are electrically non-conductive so as to generate a leakage electric field above the second layer; a communication interface coupled to one end of the first layer; a terminator on the other end of the first layer; and a first plate which is electrically conductive, the first plate being disposed on or above the second layer between the communication interface and the terminator and being a physical first length along the first axis so that a power of the radio wave received by the tag is equal to or larger than a reference value when the tag is placed at a first elevation spaced above the first plate and is placed parallel to either of the first axis, a second axis orthogonal to the first axis and parallel to the second layer, or a third axis orthogonal to the first and second axis, wherein the reference value is higher than a power of the radio wave received by the tag for any length of the first plate shorter than the first length with the tag being placed at the first elevation spaced above the first plate and parallel to the second axis.