Mutual Coupling Model Research Articles

Vortex Interaction Energy in Planar Josephson Junction Arrays at High Density

We study the vortex-vortex and vortex-antivortex interaction in arrays of Josephson junction particularly addressing the effect of mutual induction in the intermediate screening ranges (betaa = 0.5). The modifications of the barrier energy for the displacement of a vortex in presence of a second vortex (antivortex), or more vortices (antivortices), are derived in an adiabatic approach. To this end, we have developed a fast explicit algorithm, which permits to retrieve the phases and the magnetization of the array in a reasonable time and with little memory occupation for relatively large arrays [e.g. o(100 times 100)]. This new model is able to catch the essential characters of the more complex fully mutual coupling model. We provide also some indications on the relation between energy barriers and the observation of vortex quantum tunneling phenomena in Josephson arrays and related systems as high-TC films.

Neural Modeling of Mutual Coupling for Antenna Array Synthesis

Traditional synthesis methods usually deal with the Array Factor information or with approaches based on considering ideal radiating elements without interaction between them. Taking into account the coupling between elements increases the complexity of the synthesis tasks, so it is usually disregarded assuming certain error in the solution. As shown in the paper, this error can be unacceptable in some antenna array designs. A neural network-based solution can exploit the a priori knowledge of the radiating system to relate given radiated field distribution with the voltages that must be applied to each radiating element taking into account mutual coupling effects without increase of complexity from the designer's point of view. A set of techniques based on the use of neural networks for synthesis purposes are presented in this paper. Results of prototype of antenna array with feeding values designed using the proposed techniques are also presented

On the introduction of an extended coupling matrix for a 2D bearing estimation with an experimental RF system

Narrow-band DOA (direction of arrival) estimation methods need an accurate modeling of the array manifold (response of the array of antennas to one source in all directions). In radio frequency (RF) systems, electromagnetic perturbations arising from the neighborhood of the array will bring differences between the ideal and the true or measured response. If the model of the array response used in the algorithms does not take this modeling error into account, the performance of the bearing estimation methods may degrade dramatically. Usually, either a data collection of true steering vectors or a mutual-coupling model are used to perform DOA estimation in an experimental setup. The purpose of this paper is to propose an alternative to the mutual-coupling model by deriving a more accurate analytic expression of the true response. We present a model using a new extending coupling matrix, which includes the polarization and the scattering elements of the array in addition to mutual-coupling effects. An estimation of these extended and mutual coupling matrices is also originally proposed when measurements of the true steering vectors are available. The true steering vectors are measured in an experimental setup. Based on these new analytical expressions of the steering vectors of the array response, we extend the MUSIC DOA estimation algorithm to polarization diversity.

Further Study on Robust Adaptive Beamforming With Optimum Diagonal Loading

Significant effort has gone into designing robust adaptive beamforming algorithms to improve robustness against uncertainties in array manifold. These uncertainties may be caused by uncertainty in direction-of-arrival (DOA), imperfect array calibration, near-far effect, mutual coupling, and other mismatch and modeling errors. A diagonal loading technique is obligatory to fulfil the uncertainty constraint where the diagonal loading level is amended to satisfy the constrained value. The major drawback of diagonal loading techniques is that it is not clear how to get the optimum value of diagonal loading level based on the recognized level of uncertainty constraint. In this paper, an alternative realization of the robust adaptive linearly constrained minimum variance beamforming with ellipsoidal uncertainty constraint on the steering vector is developed. The diagonal loading technique is integrated into the adaptive update schemes by means of optimum variable loading technique which provides loading-on-demand mechanism rather than fixed, continuous or ad hoc loading. We additionally enrich the proposed robust adaptive beamformers by imposing a cooperative quadratic constraint on the weight vector norm to overcome noise enhancement at low SNR. Several numerical simulations with DOA mismatch, moving jamming, and mutual coupling are carried out to explore the performance of the proposed schemes and compare their performance with other traditional and robust beamformers

Mutual Coupling Compensation in UCAs: Simulations and Experiment

In a beamforming system, mutual coupling among the elements can significantly degrade the system performance. However, the mutual coupling effects can be compensated if an accurate model of mutual coupling is available. This paper utilizes a mutual coupling matrix model to compensate mutual coupling in the beamforming of a uniform circular array. In addition, a circular array of dipoles was built and measurements were performed. The predictions are compared with measurements, and verified with results from full-wave simulations

Spatial correlation in uniform circular arrays based on a spherical-waves model for mutual coupling

A general framework based on spherical waves is presented for arbitrary oriented antenna elements in a uniform circular array configuration. The technique fully describes all electromagnetic effects in the array by a set of spherical-wave coefficients. This set is limited by the overall electric size of the array. It is demonstrated that the signal correlation between the antenna elements can be calculated directly from these spherical-wave coefficients for certain statistical distributions of the directions of arrival of the incoming signals. The effects of antenna tilt on the signal correlation are investigated. It is shown that because of mutual coupling and pattern non-uniformity, signal correlation can both increase and decrease compared to the case of an ideal array consisting of isotropic and uncoupled antenna elements. Moreover, simulation results show a significant reduction of the mean channel capacity, compared to C max , for uncorrelated antenna signals and omnidirectional antenna elements.

On the simultaneous modeling of array mutual coupling and array–platform interactions

The active element patterns of antenna arrays are strongly affected by the interaction between the elements and the mounting platform. In this article a combined model is proposed to model the array response, including both mutual coupling and the platform effect. The mutual coupling is described by a coupling matrix, and the platform scattering is represented with the use of the point-scatterer model. An algorithm based on the matching pursuit concept is proposed to determine the model coefficients. Numerical results show that the active element patterns are well described by the model. © 2002 Wiley Periodicals, Inc. Microwave Opt Technol Lett 33: 167–171, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10266

A mutual coupling model for microstrip patch antenna pairs with arbitrary orientation

Mutual coupling between microstrip patch antennas, separated along their major axes and at other orientation angles, was measured and fitted, providing a simple coupling model which estimates interelement coupling between element pairs at any orientation. This information is useful in active antenna array studies where off-diagonal coupling can influence stability. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 230–233, 1998.

A mutual coupling model for microstrip patch antenna pairs with arbitrary orientation

Mutual coupling between microstrip patch antennas, separated along their major axes and at other orientation angles, was measured and fitted, providing a simple coupling model which estimates interelement coupling between element pairs at any orientation. This information is useful in active antenna array studies where off-diagonal coupling can influence stability. © 1998 John Wiley & Sons, Inc. Microwave Opt Technol Lett 18: 230–233, 1998.

Transmission line model for mutual coupling between microstrip antennas

Although more rigorous treatments have been developed for mutual coupling between microstrip antennas, the purpose of this transmission line model is to provide a numerically efficient substitute for them. Therefore, two approximations have been introduced: first, the surface waves have been neglected and second, each rectangular resonator is replaced by two equivalent radiating slots. In most practical cases the approximations are acceptable; this has been proved while comparing the transmission line model with other published results. It is obvious that the efficieney of the transmission model and can be used to include mutual coupling in practical analysis or synthesis routines for arrays of rectangular microstrip antennas.