In this letter, a dual-band magnetoelectric (ME) dipole antenna with wide operation bands is proposed for WiMAX and WLAN applications. A full-metal rectangular director is loaded right above the ME dipole antenna and it resonates at around 3.6 GHz due to the excitation of the long electric dipole (LE-dipole). Then, the lower operation bandwidth is extended significantly. This added director also allows our antenna to work as a quasi-Yagi antenna at specific frequencies, and thus, the proposed antenna is capable to achieve better unidirectional radiation performance and higher gain. In order to satisfy WLAN communication, a short trapezoid electric dipole is designed beneath the LE-dipole, which maintains the overall antenna dimensions as unchanged. Besides, such design strategy avoids the distortion of the radiation pattern at 5 GHz as well. As for the ground, a hornlike reflector is adopted instead of traditional planar structures. The measured results show that our proposed antenna achieves two wide bandwidths, 2.3-3.7 GHz (46.7%) and 5-6.25 GHz (22.2%), and high stable gain (8.5 ± 0.9 and 9 ± 1 dB) within these two operation bands.

In this paper, a novel wideband Magneto-electric (ME) dipole antenna with flat gain is proposed. The proposed antenna consists of a normal ME dipole antenna element, a substrate-printed director and a horn-like reflector (HLR). The combination of the director and ME dipole antenna element allows the proposed antenna to work as a quasi-Yagi antenna at high frequencies, which enhances its gain and front-to-back ratio (F/B ratio). The director also improves the impedance matching of the antenna, allowing a wide operation bandwidth. Using the degrees of freedom of the HLR one is able to tune the antenna gain in separate frequency bands, opening the possibility to reach the most important characteristic: a very stable gain in a wide frequency range. A prototype was fabricated and measured. The measured -10 dB bandwidth is from 1.6 to 3.8 GHz. Within the designated frequency range (1.7-3.7 GHz, incorporating the operational frequencies for 2G, 3G, 4G, Wi-Fi and WiMax), the measured gain variation is only 0.45 dB.

In this paper, a dual-band dual-sense circularly polarized (CP) magnetoelectric dipole antenna is proposed. The antenna consists of a cavity reflector, two pairs of vertical and horizontal copper plates, and a crossed Γ-shaped feeding structure. The shorted vertical plates work as quasi-magnetic dipoles (M-dipoles), while the connected horizontal plates work as electric dipoles (E-dipoles). Two M-dipoles and E-dipoles are designed to possess different heights and lengths, and thus they are able to achieve separate operation bands. To generate dualsense CP performance, the M-dipoles and E-dipoles are placed in parallel and the adjacent E-dipoles extend along the opposite directions. Benefiting from the intrinsic 90° phase difference between the M-dipole and E-dipole, the left-hand CP is achieved within the lower operation band (2.15-3.4 GHz) and the righthand CP is achieved within the upper band (4-6.3 GHz). The proposed antenna possesses a unidirectional radiation pattern with high front-to-back ratio (≥22 dB). Furthermore, high gain (≥8 dBi) and radiation efficiency (≥90%) are also achieved.

In this paper, a compact coplanar epsilon-negative (ENG) antenna is proposed with ultra-wide operation band and small size of 18x11.5 mm2. The proposed antenna is designed based on a coplanar-waveguide (CPW) feeding antenna, and thus the via-free structure is employed to realize the ENG unit cell, which is convenient to tune the frequency of zeroth-order resonance (ZOR) and extends the ZOR bandwidth. The high-order resonant frequencies are achieved and mainly determined by the separate slots that are located between the radiating patch and the ground plane. Adding the left-handed inductance between the radiating patch and ground has slight impact on the high-order resonant frequencies, and then the ultra-wide band is achieved by merging the ZOR bandwidth with the high-order resonant bandwidths. The ground plane primarily works as a matching network for the proposed antenna. Although it generates a low-frequency resonance, the performance is undesirable due to the impedance mismatching. The measured results show that the reflection coefficient, |S11| < -10 dB, is in a wide frequency range from 5.25 to 13 GHz, which covers the upper operation band of UWB communication. Also, the antenna contains relatively stable gains and omni-directional radiation patterns.