E-shaped multiple-input-multiple-output (MIMO) microstrip antenna systems operating in WLAN and WiMAX bands (between 5 and 7.5 GHz) are proposed with enhanced isolation features. The systems are comprised of two antennas that are placed parallel and orthogonal to each other, respectively. According to the simulation results, the operating frequency of the MIMO antenna system is 6.3 GHz, and mutual coupling is below −18 dB in a parallel arrangement, whereas they are 6.4 GHz and −25 dB, respectively, in the orthogonal arrangement. The 2 × 3 matrix of C-shaped resonator (CSR) is proposed and placed between the antenna elements over the substrate, to reduce the mutual coupling and enhance the isolation between the antennas. More than 30 dB isolation between the array elements is achieved at the resonant frequency for both of the configurations. The essential parameters of the MIMO array such as mutual coupling, surface current distribution, envelop correlation coefficient (ECC), diversity gain (DG), and the total efficiency have been simulated to verify the reliability and the validity of the MIMO system in both parallel and orthogonal configurations. The experimental results are also provided and compared for the mutual coupling with simulated results. An adequate match between the measured and simulated results is achieved.
A novel metamaterial, which exhibits a wideband double negative behavior in X-band, is proposed, designed, and investigated in this paper. The metamaterial is composed of modified S-shaped split-ring resonators (S-SRR). The periodic structure is designed and simulated using CST MWs. Next, the experiments are carried out, and it is shown that the simulation and the experimental results agree well and the designed structure has a wide bandwidth in X-band. An absorber application of this metamaterial is also provided, and the structure can be used as an absorber with absorption rate of over 80% for the polarization angles between 0 ∘ and 40 ∘ .
Summary
To reduce the mutual coupling between two closely microstrip antennas (MSAs), a novel ladder‐shaped conducting wall structure (LSCW) has been proposed and presented in this paper. This structure consists of two ladder shaped strips of copper printed on an FR‐4 dielectric substrate. It is inserted between the MSAs, and also some part of LSCW surrounds a portion of each antenna. The developed compact multiple‐input multiple‐output system has a compact size of 50 × 25 mm2, and dual‐band design resonates at 4.45 or 10.3‐GHz frequencies depending on the dimensions of LSCW structure. It can be used in many wireless applications in C (4‐8 GHz) band or X (8‐12 GHz) band. The value of VSWR ≤1.5 for both resonant frequencies. Also, the diversity performance, such as the envelope correlation coefficient, the diversity gain, and the total efficiency are calculated and compared. A prototype is fabricated, and the measured mutual coupling shows that the isolation between the antenna ports has been enhanced about 50 dB at 4.45 GHz and 40 dB at 10.3 GHz.
A Fishnet-Mushroom-like metamaterial electromagnetic behaviour is represented in S-parameters numerically and experimentally for X-band frequencies arena. The design has introduced a dielectric substrate as a host with metallic parts. The proposed design is predicted to provide the electromagnetic band gap characterization with desired reiterative characteristic parameters, negative permittivity, and negative permeability exhibiting a double negative left-handed region, which is identified with the X-band regime with good agreement between the simulated and the measured results.
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