Dmitry M. Ponomarev's scientific contributions

The problem of generalized scattering matrix (GSM) transformation during an angular or linear displacement of the antenna is considered. To work out the problem, it is suggested that the entries of the antenna GSM are presented as two different sets of matrices. One set is used for GSM transformation in case of antenna rotation, whereas the other in case of antenna linear displacement. Expressions have been derived that allow GSM calculation for the antenna’s new position in space from its initial, i.e. pre-displacement or pre-rotation GSM. The derived computation formulas comprise universal and independent of a particular moving antenna transformation matrices, the sizes of which are smaller than the dimension of the overall transformation matrix usually required to perform GSM calculations. Results of a practical computation verifying the derived equations are presented.

A new approach to channel modeling is proposed, in which the electromagnetic field in the scattering medium is regarded as the sum of resonance oscillation fields. Modeling starts with obtaining the scattering channel matrix that links amplitudes of spherical waves in receive-transmit regions. The scattering channel matrix provides a convenient model for MIMO communication systems, as it allows taking into account space and polarization characteristics of the fields. A method of transiting from the physical (field) to analytical (antenna) channel model is proposed, which enables taking into account multiple bounces off the antenna and surrounding objects that occur during propagation of waves. The use of the singularity expansion method (SEM) yielded accurate analytical expressions for the frequency dependence of entries of the scattering-channel matrix. The entries of the scattering-channel matrix are represented as the sum of two summands: the non-resonance summand accounting for single-bounce scattering and the resonance summand accounting for wave multiple-bounce scattering in the scattering medium. The impact of multiple-bounce scattering has been neglected in all models described earlier. A technique for building a discrete channel model for a frequency range is proposed. A set of parameters allowing the description of space-frequency characteristics of a simple-geometry wireless channel is presented. Statistical characteristics of random channel parameters are obtained, and the results of modeling such a channel are presented.

The problem under consideration here is that of building a versatile discrete antenna model in a frequency range. The eigenfunction (mode) expansion or singularity expansion method (SEM) is used in working out the problem. A detailed substantiation of SEM is provided and an expression determining the dependence of mode amplitudes on exterior source fields is derived. A simple example is provided in support of the theory. The SEM is used in inquiring into the frequency dependence of antenna-generalized matrix entries. It is intimated that all of the matrix entries contain resonance factors and factors that are Hankel transforms of radial coordinate functions. A sampling theorem, which is a generalized extension of the classic sampling theorem, is used for the Hankel transform. The application of the generalized sampling theorem completes the process of building a versatile discrete antenna model in a frequency range.

We investigate the spatial and frequency characteristics of electromagnetic fields scattered by some object. Frequency functions that allow the expression of all elements of the object scatter matrix are introduced. The sampling theorems that are proved for the introduced functions make it possible to characterize the scatterer by a set of discrete parameters. The application of the proved theorems provides for the creation of a versatile scatterer discrete model that determines the dependence of scattered fields both on spatial coordinates and frequency. A random scatterer is considered and the conditions under which the discrete parameters are statistically independent normalized random variables are stated. The article presents the results of a random scatterer modeling.

We discuss the issues of designing small-size antennas for multiple-input multiple-output (MIMO) communication systems. Introduction of the notion "potential antenna" facilitates antenna performance estimations to a great extent. Potential antenna is an idealized perfect antenna capable of absorbing the absolute entirety of information from the electromagnetic field present in a given region of space. The potential antenna concept proves instrumental in demonstrating that the optimal number of spatial subchannels for a small-size receive region in a three-dimensional (3-D) omnidirectional channel is 6. We present a compact 6-port receive antenna for 3-D wireless channels. Evidence is given to show that the suggested antenna assures a channel capacity that approximates to the theoretical limit thus making the antenna fit for use in high data rate mobile MIMO systems