This paper studies the use of antenna cluster technique in mobile antenna systems and especially its use in reducing the user effect. The study is conducted with measurements of two different antenna designs using a hand phantom to represent the user holding the device. The results show that antenna designs based on the antenna cluster technique can retain good performance in the presence of a user. Furthermore, the cluster technique can also be used to reduce the user effect by adapting the cluster operation for different environments.
The feeding coefficients maximizing the realized gain are often solved from an eigenvalue problem. We derive an alternative method for obtaining the optimal feed coefficients in this paper and show that it gives the same solution. The derived method obtains the coefficients from a direct equation. We compare the realized gain obtained with the optimal feeding coefficients to the case where the elements are progressively phased. The examples show that with optimal feeding coefficients the realized gain can be improved in cases where the mutual coupling is high, edge-element effect is strong, or the embedded element patterns are unequal. Also, an example demonstrates that circularly polarized realized gain can be improved in dual polarized array by feeding the elements with optimal coefficients.
This letter presents a method for reducing antennaexcited surface waves in mobile devices. Surface waves are canceled either by actively injecting compensating surface waves in opposite phase, or passively creating reactive conditions from which scattered, secondary surface waves cancel the primary waves. We use spherical wave expansion to calculate the amplitudes and phases of the canceling surface waves and show also how reactive loading near the antenna can launch these canceling waves. We verify the proposed method with simulations. Reduced surface waves result in a smoother radiation pattern and significantly increased gain.
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