Anastasia Gorbunova

Near-field propagation of cyclostationary stochastic electromagnetic fields

We have extended the method for modeling the stochastic EM near-field which has already been described in [5, 13] for stationary stochastic fields to the case of cyclostationary fields. Areas of application are the modeling of the electromagnetic interference radiated by digital circuitry inside the system and also into the environment, where the period of the cyclostationary EMI is given by the clock frequency of the digital circuits.

Planar stochastic sources localization algorithm in EMC problems

A two dimensional localization algorithm for stochastic EMI sources based on time domain measurements of electromagnetic near-field tangential components is presented. The autocorrelation and cross-correlation functions obtained by using the two-point planar scanning system are used for the characterization of stochastic field distribution. The simulation and experimental data are processed for a spatial localization of equivalent point sources. The estimated field distributions and patterns are presented.

Parametric reconstruction of radar image based on Multi-point Scattering Model

The wideband coherent-pulse radar provides high-resolution image of the target. The model of this image is a complex envelope superposition corresponding to signals diffracted by the point scatterers. The values of complex envelopes are distributed over the radar image coordinate plane in accordance with the point scatterer positions and their reflection coefficients. The radar image model consists of range and Doppler profiles. The parameters of the target point scatterers were defined by processing of two-dimensional (2D) data extracted from the complex 2D discrete Fourier transforms of the radar image. The proposed parametric system identification method performs the estimation of the model parameters for a short dwell time and the extrapolation of the radar data image beyond this time. The modified procedure of inverse synthesis aperture radar imaging applied to actual data showed a reduction of the Doppler smearing and some improvements of image resolution.

Equivalent circuit model for coupled monolithic integrated millimeter-wave folded antennas

Network oriented modeling of passive microwave multiports provides a useful representation of the linear device and leads to the reduction of the required computer time and memory capacity for the synthesis procedure. The Brunes multiport method allows to represent the microwave structure in the predefined frequency band as a combination of the lossless connection ideal transformers network and lossy lumped elements with a minimum number of reactive elements. The system identification procedure defines the order of the lumped elements model and the positions of poles and zeros in the complex frequency plane. The simulation of the scattering parameters for the two-port formed by two coupled folded mm-wave antennas for automotive radar applications shows a good agreement with the corresponding measurements.

A Brune's two-port process applied to lumped element filter modeling

A two-port Brunes process is applied to generate a lumped element equivalent circuit model of a Chebyshev filter of order 11 based on measured data. From the measured S parameters a rational function description is obtained by a system identification procedure applied on tabular data. This procedure consists of two main steps. The first one is a physical model order determination which can be done by using the information criteria. The second one is a linear model parameters estimation with the vector fitting method. From this rational function description the Brunes lumped element equivalent circuit is directly derived. The Brunes process allows to establish a lumped element circuit model accounting also for the circuit losses and exhibiting positive circuit elements only.

Localization of cyclostationary EMI sources based on near-field measurements

The near-field measurements of the stochastic fields radiating by digital electronic devices can be used for the localization of the stochastic electromagnetic interference (EMI) sources on the surface of device under test. The characterization of the space distribution for the wide sense cyclostationary (WSCS) stochastic field in the observation plane can be accomplished by a cross correlation between the reference and all remaining knots. The proposed Tikhonov regularization algorithm in conjunction with L-curve method provides a stable inverse reconstruction of the multi-dipole model distribution in the object plane. Parametric identification procedure based on the model order selection and two-dimensional Matrix Pencil Algorithm with subsequent fitting by Minimum Least Square technique gives the geometrical configuration of the WSCS sources. Implemented simulations and measurement experiments verified the choice of the proposed signal processing EMI sources localization algorithm.

Equivalent network synthesis for multiport microwave structures

This paper describes two approaches to equivalent network synthesis for multiport microwave structures used limited band data of Z matrix. The proposed approach is based on the simple description of the microwave structures using lumped element network. The synthesis illustrated by the example of the microstrip filter design.

System identification procedure in microwave structure modeling applications

This paper presents equivalent network synthesis techniques for lossy microwave structures. The band limited scattering parameters obtained by measurement or by full wave simulation was used for the network synthesis. This data could be represented by the transfer function of an equivalent circuit containing lumped elements (capacitors, inductances and resistances) and coupling elements (ideal transformers, mutual inductances and immattance inverters). The paper proposes two approaches to the equivalent network synthesis. The first one is based on the multiport Brune algorithm. The second one is based on the microwave structure model consisting of resonators and coupling elements between them. The synthesis procedure is illustrated by the example of the microstrip filter equivalent network design.

Equivalent circuit models for linear reciprocal lossy distributed microwave two-ports

The modeling of passive microwave structures by equivalent circuit models is an efficient technique which allows to include distributed problems into complex modeling environments at a system level. However, when synthesizing lumped element circuits for electromagnetic structures with large internal propagation delays, the obtained impedance functions exhibit a large number of frequency poles in a given frequency rang. Hence, the equivalent circuit models are represented by a large number of lumped circuit elements. The number of circuit elements can be reduced significantly if also delay lines are included in addition to capacitors, inductors, resistors, and ideal transformers. We discuss a systematic procedure for the generation of combined lumped element and delay line equivalent circuit models on the basis of numerical data is described.

Stochastic EMI sources localization based on time domain near-field data

The paper presents a planar stochastic EMI sources localization approach based on two-point time-domain data of electromagnetic near-field tangential components. The radiating structure is considered as a set of simple electrical dipoles arranged on a grid in the object plane. The autocorrelation and cross-correlation spectra of eradiated signals in two different space points are used to determine the distribution of dipole moments and to identify the parameters of the effective radiation sources. The modeling data was processed with the proposed localization procedure.