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Alaee, R.; Albooyeh, M.; Yazdi, M.; Komjani, N.; Simovski, C.; Lederer, F.; Rockstuhl, C. We explore the optical properties of a meta-atom made of plasmonic nanopatches that possess an increasing degree of complexity. We show that if two nanopatches are strongly coupled and have a different geometrical footprint, the meta-atom exhibits a resonant magnetoelectric response, in addition to the anticipated resonant electric and magnetic response. Thus, it behaves similarly as the so-called omega particle, but with the unique advantage that frequency and strength of this magnetoelectric resonance can be independently tuned and modified with respect to the corresponding values of the electric resonance. This allows a metasurface of such meta-atoms to possess widely controlled reflection and transmission coefficients, e.g., the regimes of strongly asymmetric reflectance and perfect absorption become possible. Alternatively, an individual meta-atom of such kind can act as a directive nanoantenna with zero backscattered fields (Huygens' scatterer). Magneto-electric coupling in nonidentical plasmonic nanoparticles: Theory and applications

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A novel broadband unit-cell is proposed in this paper. This new cell element consists of three coupled circular rings where four quasi-spiral delay lines are connected to the outer ring to provide the required phase shift. The spiral shape of the delay lines exhibits more than 1000 o of phase swing. The cross polarization level of the presented element is considerably improved compared to previous designs with a similar phasing mechanism. The capability of operating in linearly or circularly polarized incident wave is an important advantage of the proposed cell. In other words, depending on polarization of the feed antenna, the present reflectarray can operate in vertical, horizontal or circular polarization. Finally a moderate size reflectarray, 27×27 cm 2 , is designed and fabricated based on the mentioned element. The measured results showed about 16.5% of 1 dB gain bandwidth. The antenna gain at 8.5 GHz is 26.4 dB which is equivalent to 59.2% efficiency. Also, the measured sidelobe level and cross polarization of this antenna are about -20 dB and -25 dB, respectively.Index Terms-Quasi-spiral phase delay line, phase shift mechanism, reflectarray antenna, delay line.

Abstract-In this paper, we present a novel approach for improving the bandwidth of a microstrip patch antenna using Jerusalem crossshaped frequency selective surfaces (JC-FSSs) as an artificial magnetic ground plane. The invasive weed optimization (IWO) algorithm is employed to derive optimal dimensions of the patch antenna and JC-FSS element in order for the whole structure to work at 5.8 GHz with consideration of gain. For the most efficient design, the antenna and FSS ground plane are optimized together, rather than as separate components. Simulation results demonstrate that this optimum configuration (the microstrip patch antenna over the artificial magnetic ground plane) have a broad bandwidth of about 10.44%. This wide bandwidth is obtained while the thickness of the whole structure is limited to 0.1λ. Further more desirable radiation characteristics have been successfully realized for this structure. The radiation efficiency of the AMC antenna configuration was found to be greater than 85% over the entire bandwidth. In general by introducing this novel Jerusalem cross artificial magnetic conductor (JC-AMC) in lieu of the conventional perfect electric conductor (PEC) ground plane, the bandwidth enhancement of about 67% and a thinner and lighter weight design has been obtained. Sample antenna and EBG layer are also fabricated and tested, to verify the designs. It is shown that the simulation data in general agree with the measurement results for the patch antennas implemented with FSS ground plane.

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This paper presents a novel tunable terahertz antenna based on a hybrid graphene-metal structure fed by a waveguide. First, the hybrid plasmonic waveguide is studied by analytical and numerical methods. Then, an efficient terahertz antenna is designed by an analytical approach using the transmission line model. The antenna performances are evaluated in the terahertz frequency band by a full-wave electromagnetic solver. Contrary to previous terahertz antennas based on graphene, the results show that the proposed antenna has satisfactory radiation efficiency and gain. Moreover, this study demonstrates that the reflection parameter of the antenna can be tuned by the chemical potential of graphene. The proposed antenna can be applied for terahertz applications such as wireless communication in interand intra-chip devices and sensing.

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