Zero-phase-shift line antennas

The electric current flowing along a zero-phase-shift (ZPS) line, or segmented line features very less phase lag. The utilization of the ZPS line to configure a segmented loop antenna makes the current along the loop antenna unchanged in phase and flowing in a single direction even when the perimeter of the loop is up to several operating wavelengths. Using such a characteristic, the electrically large segmented loop antenna for ultra high frequency (UHF) near-field radio frequency identification (RFID) applications, horizontally omnidirectional antenna, and circularly polarized omnidirectional antenna for wireless local area network (WLAN) applications have been designed. In this paper, the state-of-art antenna designs using the ZPS segmented line are reviewed and presented.