Low Profile Metal Tolerant UHF RFID Tag With Lumped Elements for Post-Manufacturing Frequency Tuning

In this communication, a planar inverted-F antenna (PIFA) structure is employed for the realization of a compact and low profile metal mountable tag device for ultrahigh-frequency (UHF) radio frequency identification (RFID). In order to compensate dielectric parameters and/or tag chip impedance variations, and the effects of manufacturing tolerances or other imperfections which can cause severe performance degradation at the target frequency, a tag structure with three lumped elements and a U-shape slot with adjustable length for post-manufacturing working frequency and impedance matching tuning is proposed. In order to simplify the post-manufacturing tuning process, both the PIFA and the tag chip matching network are designed to match an intermediate
$50~\Omega $
real impedance, which makes it possible to easily verify the impedance matching performance. A
$29.8\times 29.8\times0.813$
mm
³
prototype is manufactured for the 920.5–924.5 MHz Chinese bandwidth, and it has been verified that the post-manufacturing tuning operation can effectively restore the design working frequency, with a read range of 3.6 m at 922.5 MHz when the tag is mounted on a
$10\times10$
cm
²
aluminum plate.