Inductively Loaded Segmented Loop Antenna by Using Multiple Radiators

This letter presents a study of inductively loaded segmented loop antenna (SLA) by using multiple radiators. The identical radiators are stacked by multiple layers and excited in parallel. Through the study, it is found that the radiators can generate strong mutual inductive couplings, which induce extra mutual inductance in each unit cell. As a result, the physical dimensions of the antenna can be reduced to compensate the frequency shift caused by the couplings. In addition, by loading the radiators, the near-field radiation performance of the antenna is enhanced. It addresses the problem that smaller loop antenna often has lower field intensity. In this letter, single-layer (SL) (conventional), double-layer (DL), and triple-layer (TL) SLAs are demonstrated and compared theoretically and experimentally. The study shows that DL and TL antennas have 32$\%$ and 58$\%$ area reductions compared to the SL antenna, respectively. The proposed antenna can be a good candidate for the radio frequency identification system.