Compact Crossed-Dipole Antennas Loaded With Near-Field Resonant Parasitic Elements

Electrically-Small Circularly-Polarized Quasi-Yagi Antenna

“…The proposed design yielded a |S 11 | < −10 dB bandwidth of 1.477-1.748 GHz (16.8%) and a 3-dB AR bandwidth of 1.508-1.628 GHz (7.7%) with two minimum AR points at 1.523 GHz (AR = 0.76 dB) and 1.596 GHz (AR = 1.72 dB). This bandwidth-enhanced phenomenon was presented and discussed in [13]; i.e., the parasitic elements are designed to work as near-field resonant parasitic elements, which produce the extra resonances and CP radiations for the antenna system. These extra ones are combined with the resonances and CP radiations caused by the driver to broaden the antenna bandwidth.…”

“…However, the main drawback of these CP ESAs is narrow axial ratio (AR) bandwidth, i.e., their 3-dB AR bandwidths are approximately 1% or less. In order to achieve a directive radiation, the near-field resonant parasitic (NFRP) element was designed to act a reflector of the crossed dipole antenna [13]. The NFRP reflector just strongly affects the directive pattern in the low-frequency region, and therefore, the unidirectional radiation is not very good in the high-frequency region.…”

Polarizations of Crossed-Dipole Antenna Loaded With Different NFRP Elements

“…Therefore, the configurations of these antennas are complicated, and consequently, it is relatively difficult to implement the CP NFRP antennas for multiband operations or enhance their operational bandwidths. Recently, the crossed-dipole NFRP antennas [10,11] have been reported for dual-band and broadband operations. In these studies, both crossed-dipole and NFRP elements were designed to generate CP radiations, which are utilized for the dual-band and broadband operations.…”

“…In these studies, both crossed-dipole and NFRP elements were designed to generate CP radiations, which are utilized for the dual-band and broadband operations. Moreover, as mentioned in [10], an interesting phenomenon is that the polarization of the antenna can be changed by a physically adjusting the NFRP element. However, this phenomenon has not been rigorously pursued.…”

“…The antenna was placed above a 150 mm × 150 mm ground plane at a distance of H a . Its primary radiating elements are the same as those of the design presented in [10], which were printed on two substrates made of Rogers RT/duroid 5880 material (ε r = 2.2 and tan δ = 0.0009) with thickness h s1 = h s2 = 0.508 mm. The substrates were stacked together with no air gap.…”