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In this paper, a single-layer wideband differential-fed microstrip patch antenna (DMPA) with complementary split-ring resonators (CSRRs) loaded is proposed. First, a quarter-wave microstrip-line resonator is introduced as a capacitive coupling feeding structure which can generate a non-radiative resonant mode. Second, a set of rectangular parasitic patches is loaded co-planarly along the non-radiative edges of the DMPA. Thus, a parasitic radiative mode at the high side of the operation band is added. Meanwhile, with this arrangement, the field distribution of the DMPA has also changed, and a radiation null at high band edge is formed. Then, a pair of CSRRs is etched on the ground beneath the feeding lines, which has compensated the mismatched impedance of the DMAP at the low side of the operation band. As a result, the low-frequency bandwidth is significantly increased. Finally, the proposed antenna is fabricated and measured, and the measured results are in good agreement with the simulation ones. The measured bandwidth of the proposed antenna is ranged from 5.35 GHz to 7 GHz (about 26.7%) while keeping a low profile of 0.051λ (λ is the free-space wavelength at the center frequency) without any air gaps. Besides, the broadside gain is from 7.7 dBi to 10.7 dBi. INDEX TERMSDifferential-fed patch antenna, wideband antenna, single-layer, parasitic patches, complementary split ring resonator. YI-XUAN ZHANG (S'18) received the B.Eng. degree in electronic information engineering from Xidian University (XDU), Xi'an, China, in 2017, where he is currently pursuing the Ph.D. degree with the Department of National Key Laboratory of Antennas and Microwave Technology. His current research interests include high performance electromagnetic optimization, phased array, and 5G communication technology.

The process of p-type doping for GaN nanowires is investigated using calculations starting from first principles. The influence of different doping elements, sites, types, and concentrations is discussed. Results suggest that Mg is an optimal dopant when compared to Be and Zn due to its stronger stability, whereas Be atoms are more inclined to exist in the interspace of a nanowire. Interstitially-doped GaN nanowires show notable n-type conductivity, and thus, Be is not a suitable dopant, which is to be expected since systems with inner substitutional dopants are more favorable than those with surface substitutions. Both interstitial and substitutional doping affect the atomic structure near dopants and induce charge transfer between the dopants and adjacent atoms. By altering doping sites and concentrations, nanowire atomic structures remain nearly constant. Substitutional doping models show p-type conductivity, and Mg-doped nanowires with doping concentrations of 4% showing the strongest p-type conductivity. All doping configurations are direct bandgap semiconductors. This study is expected to direct the preparation of high-quality GaN nanowires.

A wideband magneto‐electric dipole antenna with a claw‐shaped reflector is presented for future 5G communication systems. A pair of E‐shaped radiating patches is used to form an electric dipole, while two folded patches, which are shorted to the ground, are used as the magneto dipole. Four inverted‐L parasitic branches are introduced on the four corners of the ground, producing new resonant points. The four parasitic branches along with the ground plane form a claw‐shaped reflector for the antenna to obtain stable directional radiation patterns. This antenna is fed by a modified feeding structure to improve the matching of the working band. The measured results show that the reflection coefficient is less than ‐10 dB in a relative bandwidth of 103.6% (1.18‐3.72 GHz). The average gain in the working band is around 7.6 dBi. As a result, the proposed antenna can be a favorable candidate for future 5G communication systems.