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Exploiting highly directional antenna arrays to compensate for severe propagation loss is one of the defining features in millimeter-wave (mmWave) communications. With efficient beamforming techniques, mmWave transceivers can form steerable narrow beams. Therefore, different from convenient microwave networks, the signal or interference power in mmWave communications is highly directional and closely related to critical parameters such as interference distance and angles of departure/arrival. The high directivity implies that the co-channel interference among simultaneously active mmWave links can be expected to be significantly smaller than that for omnidirectional links and, meanwhile, the security of mmWave communications may also be enhanced. In this context, will the traditional interference mitigation and physical-layer security techniques still be efficient or necessary in mmWave networks? The answer may be negative in certain conditions. However, there is no detailed analysis on the conditions for this issue. In this paper, we jointly analyze the inter-beam interference and secrecy performance of mmWave communications for their close relation to signal-to-interference-plus-noise ratio. We also derive various performance limits (e.g., interference/eavesdropping distance limit, transmission power limit, offset angle limit, and beamwidth limit) of interference and eavesdropping immunity in mmWave networks. The theoretical and numerical results verify our analysis.

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The subject of this paper is the calculation of charge distribution on the surfaces of thin conducting microelectromechanical systems beams, of nearly square cross-section, in electrostatic problems, by the boundary element method (BEM). A line model of a beam is proposed here. This model overcomes the problem of dealing with nearly singular matrices that occur when the standard BEM is applied to very thin features (objects or gaps). This new approach is also very efficient. Numerical results are presented for selected examples. Copyright © 2007 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The narrow beams with very low sidelobes are generated from an array of nonidentical elements. The array considered in the present work is found to be more advantageous than the array of identical elements in terms of main breamwidth and side-lobe levels, excitation levels being uniform in both cases. [ABSTRACT FROM AUTHOR]