A multi-functional button antenna is designed, with dual-band and dual-polarization characteristics. This antenna is a dedicated design for wearable applications. A compact size button is achieved with a diameter of only 19.5 mm (0.29 λ), which optimizes the users' comfort. The proposed antenna works in the 4.5-4.6 unlicensed future 5G communication band, and the 5.1-5.5 GHz WLAN band. Two radiation patterns with orthogonal linear polarizations are obtained in each band. The mutual coupling between the two patterns is below -20 dB. The antenna is prototyped. Simulations and experiments confirm the validity of this novel concept.
In this paper, we study the effect of element separation in a base station array (BSA) on the downlink line-of-sight achievable sum-rate of MIMO systems in the presence of mutual coupling at the BSA. The channel matrix H is modeled using the embedded field patterns of the BSA and is used to analyze the outage performance for two single-element user equipments assuming no inter-user coupling.
In this paper we compare different iterative techniques enhanced by the CBFM, that are used to analyze finite arrays of disjoint antenna elements. These are based on the stationary-type methods (Jacobi, Gauss-Seidel, macro-block Jacobi), the nonstationary GMRES and the hybrid alternating GMRES-Jacobi (AGJ) method which combines these two types. In each iteration, the reduced CBFM system is constructed based on the previous iterates, the solution of which is used to update the solution vector in the next iteration with improved accuracy. In this way, the convergence of the classical iterative techniques can be greatly improved. The convergence rates and computational costs of the CBFM-enhanced iterative methods are analyzed by considering several MoM-based problems. The GMRES-based method, which employs the block-Jacobi preconditioner, outperforms the other methods when the MoM matrix is ill-conditioned. For well-conditioned MoM matrices with reduced diagonal dominance due to increased presence of the inter-element coupling effects, the AGJ method or the methods based on the stationary-type iterations may require smaller computational effort to converge to the desired solution accuracy in comparison to the GMRES-based approach.
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