Physical Modeling of MIMO Antennas and Channels by Means of the Spherical Vector Wave Expansion

Författare

Andres Alayon Glazunov
Mats Gustafsson
Andreas Molisch
Fredrik Tufvesson

Summary, in English

In this paper we propose a new physically motivated model that allows to study the interaction between the antennas and

the propagation channel for Multiple-Input Multiple-Output (MIMO) systems.

The key tools employed in the model are the expansion coefficients of the electromagnetic field in

spherical vector waves and the scattering matrix representation of the

properties of the antenna. We derive the expansion of the MIMO

channel matrix, H, in spherical vector wave modes of

the electromagnetic field of the antennas as well as the propagation channel. We also introduce the channel scattering dyadic, C,

with a corresponding correlation model for co- and cross-polarized elements

and introduce the concept of mode-to-mode channel mapping, the

M-matrix, between the receive and transmit antenna modes. The M-matrix maps the modes excited by the

transmitting antenna to the modes exciting the receive antennas and vice

versa. The covariance statistics of this M-matrix are expressed as a function

of the double-directional power-angular spectrum (PAS) of co- and

cross-polarized components of the electromagnetic field. Our approach

aims at gaining insights into the physics governing the interaction between

antennas and channels and it is useful for studying the

performance of different antenna designs in a specified propagation channel

as well as for modeling the propagation channel. It can furthermore be used to

quantify the optimal properties of antennas in a given propagation channel.

We illustrate the developed methodology by analyzing the interaction of a 2x2 system of slant polarized half-wavelength dipole antennas with

some basic propagation channel models.

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