Improvement of multiple loop antenna for near-field UHF RFID applications

Considering High-Performance Near-Field Reader Antennas: Comparisons of Proposed Antenna Layouts for Ultrahigh-Frequency Near-Field Radio-Frequency Identification

“…5b where two square segmented loops share a common edge [23]. Two concentric segmented loops are proposed in [24] to enhance the magnetic field distribution. Dash-line segmented loop antennas have been used in various applications, such as an innovative animals tracking system [25] and a bracelet directly integrated into clothes [26].…”

Broadband cross dipole antenna for UHF near-field RFID applications

“…As the most common type of the near-field RFID reader antenna, loop antenna is the first choice to be used at UHF band [12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]. However, due to the inverse current, the conventional loop antenna could generate the blind area.…”

“…However, due to the inverse current, the conventional loop antenna could generate the blind area. Therefore, many researchers have been studied to modify the electrically-large loop antenna, such as segmented loop antenna with lumped capacitors [12], zero-phase-shift line (ZPSL) [13,14,15,16,17,18,19,20,21,22,23,24], several diploes to form the loop antenna [25,26,27,28,29] and other modified loop antenna [30,31]. The other popular type of UHF near-field reader antenna is based on the oppositely directed currents (ODCs) [32,33,34,35,36,37,38].…”