| 摘要 |
<p>A monitor tag (30) having a radio frequency transmitter (32) and a patch antenna (10). The antenna is in communication with the transmitter and has a first conductive patch (12) and a second conductive patch (16) substantially parallel to each other, and separated from each other by a dielectric material (18) in contact with both patches and having a thickness sufficient to create a gap between the patches wherein the radiation resistance will be controlled during operation of the antenna. The first conductive patch has a dimension of one-quarter or one-half wavelength, depending upon available space and desired pattern. Because the electric field is launched from the gap between the patches and is highly concentrated, bringing the monitor tag close to a metal object or attaching it thereto will have minimal impact on the impedance of the antenna.</p> |
