-A new particle swarm optimization (PSO) technique for electromagnetic applications is proposed. The method is based on quantum mechanics rather than the Newtonian rules assumed in all previous versions of PSO, which we refer to as classical PSO. A general procedure is suggested to derive many different versions of the quantum PSO algorithm (QPSO). The QPSO is applied first to linear array antenna synthesis, which is one of the standard problems used by antenna engineers. The performance of the QPSO is compared against an improved version of the classical PSO. The new algorithm outperforms the classical one most of the time in convergence speed and achieves better levels for the cost function. As another application, the algorithm is used to find a set of infinitesimal dipoles that produces the same near and far fields of a circular dielectric resonator antenna (DRA). In addition, the QPSO method is employed to find an equivalent circuit model for the DRA that can be used to predict some interesting parameters like the Q-factor. The QPSO contains only one control parameter that can be tuned easily by trial and error or by suggested simple linear variation. Based on our understanding of the physical background of the method, various explanations of the theoretical aspects of the algorithm are presented.

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We develop a general approach to cross correlation in antenna systems suitable for applications to spatial diversity and MIMO systems. The far-field correlation is expressed in terms of the currents on the antennas. The basic strategy proposed here is to perform the overall evaluation of cross correlation by means of superposition integrals involving contributions emerging from all possible mutual correlations between the point sources on the antenna currents where interactions are mediated by a new cross correlation Green's function. The method is verified and demonstrated in several numerical examples and a design methodology aiming at maximizing the diversity gain is outlined and illustrated. It is also shown that arbitrary antenna arrays can be reduced to suitable models involving only infinitesimal dipoles, in effect enabling us to compute the total diversity gain using the cross correlation Green's function. The formulation provided here gives the electromagnetic aspect of spatial diversity an articulated form proper for design and development of practical communication links using multiple antenna systems.

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Abstract-We study theoretically the propagation of electromagnetic waves in an infinite and homogenous medium with both temporal and spatial dispersion included. We derive a partial differential equation connecting temporal and spatial dispersion to achieve negative group velocity. Exact solutions of the equation are found and shown to lead to the possibility of exciting constant negative group velocity waves. We then investigate the effect of spatial dispersion on the power flow and derive the first-, second-, and third-order corrections of power flow due to the nonlocality in the medium. This derivation suggests a path beyond the group velocity concept.

The recently introduced quantum particle swarm optimization (QPSO) algorithm is employed to find infinitesimal dipole models (IDM) for antennas with known near-fields (measured or computed). The IDM can predict accurately both the near-fields and the far-fields of the antenna. A theory is developed to explain the mechanism behind the IDM using the multipole expansion method. The IDM obtained from single frequency solutions is extrapolated over a frequency range around the design frequency. The method is demonstrated by analyzing conductingand dielectric-type antennas. A calibration procedure is proposed to systematically implement infinitesimal dipoles within existing method of moment (MoM) codes. The interaction of the IDM with passive and active objects is studied through several examples. The IDM proved to predict the interaction efficiently. A closed-form expression for the mutual admittance between similar or dissimilar antennas, with arbitrary orientations and/or locations, is derived using the reaction theorem.Index Terms-Infinitesimal dipole model, multipole expansion, mutual coupling.

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