No abstract

In this paper three different multi stub antenna arrays at 27–29.5 GHz are designed. The proposed antenna arrays consist of eight single elements. The structure of feeding parts is the same but the radiation elements are different. The feeding network for array is an eight way Wilkinson power divider (WPD). To guarantee the simulation results, one of the proposed structures is fabricated and measured (namely the characteristics of S11, E-, and H-plane patterns) which shows acceptable consistency with measurement results. The simulation results by CST and HFSS show reasonable agreement for reflection coefficient and radiation patterns in the E- and H- planes. The overall size of the proposed antenna in maximum case is 29.5 mm × 52 mm ×  0.38 mm  (2.8 $${{\varvec{\lambda}}}_{0}$$ λ 0 × 4.86$${{\varvec{\lambda}}}_{0}$$ λ 0 × 0.036$${{\varvec{\lambda}}}_{0}$$ λ 0 ). Moreover, for Specific Absorption Rate (SAR) estimation, a three-layer spherical human head model (skin, skull, and the brain) is placed next to the arrays as the exposure source. The simulation results show that the performance of proposed antennas as low-SAR sources makes them ideal candidates for the safe usage and lack of impact of millimeter waves (mmW) on the human health. In all three cases of SAR simulations the value of SAR1g and SAR10g are below the standard limitations.

The performance of an antenna array is considerably affected by mutual coupling effects between antenna elements. When a large number of antenna elements are located close to each other, mutual coupling becomes more significant. In this study, by using a new mutual impedance matrix, a decoupling methodology for compensating mutual coupling effects in a practical very high frequency (VHF)/ultra high frequency (UHF) Yagi-Uda antenna array is introduced. No previous publications have studied VHF/UHF Yagi-Uda antenna arrays in this context. In the proposed scheme, extreme care has been taken to account for both self-and mutual impedance related to mutual coupling effects. Experimental and simulation results show that using the proposed method, a perfect decoupling is achieved. The application of high-resolution direction of arrival (DOA) estimation algorithms in decoupled experimental data leads to excellent performance of DOA estimation, in terms of accuracy and resolution. In addition, it is concluded (from experimental and simulation results) that mutual coupling effects between array elements as well as the root-mean-square error of estimated parameters depend on the direction of arrival. It is also deduced that in the presence of mutual coupling, estimation of signal parameter via rotation invariance techniques algorithm performs better than other subspace-based algorithms.

This article proposes a novel mutual impedance matrix model for compensating mutual coupling effects in adaptive array with application to adaptive nulling of interference signals. In the new method, extreme care has been taken into account for both self impedance and mutual impedance, relating to the mutual coupling effects. Numerical simulation results demonstrate the robustness and capability of this technique. By using the new method, it is found that both the accuracy of the positioning and depth of the nulls are significantly improved. Performance comparisons of the new methodology and several other previous techniques via a number of simulation are presented. V C 2013 Wiley Periodicals, Inc.Int J RF and Microwave CAE 24:30-38, 2014.

No abstract