Antenna Array Geometry Research Articles

Optimum Ambiguity-Free Directional and Omnidirectional Planar Antenna Arrays for DOA Estimation

This paper studies the antenna array geometry impact on both direction of arrival (DOA) estimation accuracy and array rank ambiguity. Some restrictions are imposed on the array geometry that guarantee first-order ambiguity-free arrays and, at the same time, reduce the cost of a global systematic optimization. The subsequently derived Cramer-Rao bound (CRB) on the DOA estimates shows to be attractive for numerical evaluation. Depending on whether the DOA estimation accuracy is desired to be uniform in all possible directions or is to be enhanced in a given aperture around some privileged direction, two optimization problems are formulated and solved by exhaustive search to compute the optimal array geometries. The obtained optimal arrays significantly outperform their circular counterparts and tend to have a form close to the V shape. We study in details V-shaped arrays and derive asymptotic performance measures that apply for large sized arrays where exhaustive search is unaffordable.

On physically-based normalization of MIMO channel matrices

Various normalizations of the MIMO channel matrix are discussed from a physical perspective. It is demonstrated that the physics of antenna arrays and propagation channel should be taken into account when normalization is chosen, so that SNR has proper physical meaning, the conclusions are physical and correspond to realistic systems. The antenna array geometry and the transmission strategy (coherent/non-coherent) limits the choice of normalization and determines how the capacity and other performance metrics scale with the number of antennas, which is more pronounced for densely-populated antenna arrays. This is especially important for an asymptotic analysis, when the number of antennas increases to infinity. Limitations of such analysis from the physical perspective are pointed out.

Optimizing Antenna Array Geometry for Interference Suppression

The determination of an optimum antenna array geometry for suppressing interference is addressed. An optimization problem is derived whose solution yields an optimum array geometry for a given interference environment. A specific example is solved via the Simulated Annealing Optimization algorithm and results are presented for arrays of varying configurations

Geometric Design of Pyramidal Antenna Arrays for Hemispherical Scan Coverage

An approach is presented for optimizing the geometry of pyramidal antenna arrays, given a full azimuth and a full or limited elevation scan requirement. It involves choosing the best face elevation and number of faces of the pyramid, which minimize the maximum scan angle while maximizing the geometric directivity. The analysis shows that the 4-face pyramid is the best choice. The derivation assumes that the distance to the antenna is infinite (the true far-field case). However, when finite distances are considered, the maximum scan angle increases only slightly at the minimum far-field distance used for low sidelobe pattern measurement

EFFECT OF ANTENNA ARRAY GEOMETRY AND ULA AZIMUTHAL ORIENTATION ON MIMO CHANNEL PROPERTIES IN URBAN CITY STREET GRID

Propagation environment and antenna array configuration have significant effect on spatial correlation properties of multiple- input multiple-output (MIMO) wireless communications channels. In this paper the effect of different antenna array geometries on MIMO channel properties is investigated in urban city street grid propagation environment. Four antenna array geometries with the same number of antenna elements and fixed inter-element spacing are considered, namely, uniform linear array (ULA), uniform circular array (UCA), uniform rectangular array (URA) and uniform cubic array (UCuA). The effect of ULA orientation in azimuthal plane on MIMO channel ergodic capacity is also investigated. Varying orientation angle from 0 to π at the two communication ends is considered. The investigation is carried out based on three dimensional (3D) spatial multi-ray realistic propagation channel model covering different propagation types. It is shown that the antenna array geometry have significant impact on MIMO channel properties. Under different propagation scenarios the ULA shows superiority to the other considered geometries in terms of the ergodic channel capacity and number of spatial parallel channels. However, this superiority depends largely on the array azimuthal orientation.

Cramer-Rao bounds for antenna array design

We study the impact of the geometry of the (planar) antenna array on the accuracy of the estimated direction(s) of arrivals of an emitting source. We develop explicit Cramer-Rao bounds (CRBs) of the azimuth and elevation angles that show a simple structure. In particular, for a fixed elevation angle, the CRBs are cosine functions of the source azimuth, and so, regardless of the array geometry. The amplitude and extremes of these functions depend on the array geometry. Hence, the array configuration can be chosen in order to ensure a desired (an)isotropic behavior. To do so, we propose a pragmatic methodology that also takes into account the array ambiguity problem. The array design problem is simplified by limiting the array search within a family of V-shaped arrays that are advantageously characterized by a single parameter, the angle between the two branches. A performance measure is proposed, then analytically expressed, to assess the array directivity and gain with respect to the more standardly used uniform circular array.

HFSWR based on synthetic impulse and aperture processing

A novel high-frequency surface wave radar (HFSWR) has been proposed, which is based on the principles of synthetic impulse and aperture processing. It uses multiple omnidirectional transmit antennae to simultaneously transmit a set of orthogonal waveforms, and the echoed signals are received and processed by one or multiple reception arrays. Although the transmit beam pattern is omnidirectional, by proper processing, the received signal multiple equivalent directional transmit beam patterns can be simultaneously formed. The signal processing scheme to obtain equivalent directional transmit beam pattern is investigated in detail. Considerations for system parameter selection to achieve an overall best system performance are proposed and discussed. In particular, for the novel HFSWR, target range and angle estimates are coupled together due to the orthogonality of the transmitted waveforms. A necessary and sufficient condition on the transmit antenna array geometry and transmit frequencies, which ensures that target range and angle estimates are uncoupled, is presented.

Theoretical analysis of ion cyclotron range of frequency antenna array for HT-7U

This paper considers the coupling analysis of phased antenna array designed to excite fast wave in the ion cyclotron range of frequency. The coupling of the antenna is calculated in slab geometry. The coupling code based on the variational principle gives the self-consistent current flowing in the antenna, this method has been extended so that it can be applied to a phased antenna array. As an example, this paper analyses the coupling prosperities of a 2×2 phased antenna array. It gives the optimum geometry of antenna array. The fields excited at plasma surface are found to more or less correspond to the antenna current phasing.

Application of a nonlinear method of restoration in combination with sparse antenna arrays in radiometric imaging systems

The paper considers methods of elimination of diffraction distortion in radio-engineering imaging systems with sparse antenna arrays. At the first stage the problem of synthesis of antenna array geometry is resolved, while at the second — processing of images is performed by the nonlinear method with constraints. The paper includes results of imitative simulation of the process of creation and reconstruction of images in the radiometric system.

Degrees of Freedom in Multiple-Antenna Channels: A Signal Space Approach

Multiple-antenna systems that are limited by the area and geometry of antenna arrays, are considered. Given these physical constraints, the limit on the available number of spatial degrees of freedom is derived. The commonly used statistical multiple-input multiple-output (MIMO) model is inadequate. Antenna theory is applied to take into account the area and geometry constraints, and to define the spatial signal space so as to interpret experimental channel measurements in an array-independent but manageable description of the physical environment. Based on these modeling strategies, for a spherical array of effective aperture A in a physical environment of angular spread |/spl Omega/| in solid angle, the number of spatial degrees of freedom is shown to be A|/spl Omega/| for uni-polarized antennas and 2A|/spl Omega/| for tri-polarized antennas. Together with the 2WT degrees of freedom for a system of bandwidth W transmitting in an interval T, the total degrees of freedom of a multiple-antenna channel is therefore 4WTA|/spl Omega/|.

The method of lines for mutual coupling analysis of a finite array of patch antennas on a cylindrical stratified structure

We present an application of the method of lines (MoL) for the analysis of a finite array of microstrip patch antennas loaded with dielectric layers on a cylindrical structure. New formulas are given in cylindrical coordinates to describe multiple, stacked layers without causing an increase in the difficulty or complexity of the analysis. We show that this model is not only numerically efficient, compared with other numerical methods, but also, shows a very good accuracy with respect to experimental results and has no limitation on antenna array geometry and excitation. Finally, some numerical results for both radiation and mutual coupling are presented.

Design of Nonuniform Linear Antenna Array Geometry and Signal Processing Algorithm for DOA Estimation of Gaussian Sources

Abramovich, Yuri I., and Spencer, Nicholas K., Design of Nonuniform Linear Antenna Array Geometry and Signal Processing Algorithm for DOA Estimation of Gaussian Sources, Digital Signal Processing10 (2000), 340–354.This paper discusses the problem of direction-of-arrival (DOA) estimation for Gaussian sources that have arbitrary correlation: from independent to fully correlated. For independent sources, the antenna array design is governed by two competing considerations: maximum aperture, which inclines toward increasing sparsity for a given number of array sensors, and identifiability, which tends to exclude extreme sparsity. For fully correlated sources, these two competing criteria are augmented by a third which allows for the initialization of DOA estimation by the generalized spatial smoothing (GSS) technique. The maximum number of fully correlated sources is in turn an important factor in the GSS algorithm and subsequent array geometry design. We present a geometry optimization technique that permits accurate DOA estimation of arbitrarily correlated sources.

Placing Quasi-Nulls in Planar and Conformal Arrays

ABSTRACT We describe the use of the simulated annealing optimization method to introduce minimal modifications in the excitations and/or geometries of planar and circular arc antenna arrays so as to depress the radiation pattern in arbitrary directions while maintaining side lobe levels and beamwidth.

A Comparison of Various High Resolution Spectral Estimation Techniques in Radio Direction Finding

Due to the progress in the signal processing hardware, high resolution spectral estimation algorithms now become applicable in practical systems. One favour application is radio direction finding (DF) used for navigation and electronic reconnaissance. Compared with classical DF techniques the advantage of the high resolution methods is their better resolution capability in interference fields and the ability to use nearly every possible antenna array geometry. Nevertheless, the better resolution capability may decrease in practice due to model and DF system errors. In this paper we will compare three high resolution spectral estimation techniques, namely the MUSIC (MUltiple SIgnal Classification), the Minimum-Norm and the Capon algorithm. As a reference, the classical Fourier algorithm is also treated. The results show, that two algorithms, MUSIC and Fourier, are applicable in practice. Furthermore a simple method to reduce the computational effort of calculating the angle spectrum is given, which has to be calculated for all four methods.

A circuit model for mutual coupling analysis of a finite antenna array

Mutual coupling effects within an antenna array play a very important role in the areas of EMC (electromagnetic compatibility) and antenna array design. A circuit model is developed to represent the input admittance of an antenna array with a finite number of elements. This model consists of a component to represent the input admittance of an isolated antenna element and infinite shunt components with each to represent different degrees of antenna mutual coupling effects. Twersky's (1952) algorithm of multiple scattering analysis is used to illustrate the physical meaning of each circuit component. Numerical results show that good accuracy for the antenna input admittance calculation can be obtained by using this model to the second order approximation. As the array is large and sparse, a very small amount of computation can yield good accuracy. This model is shown not only to be numerically efficient compared to the full wave analysis using the moment method, but also to give a physical insight into the antenna array mutual coupling mechanism. Furthermore, this model has no limitation on antenna array geometry and excitation.

Direction finding in multipath environment using method of alternating projection

In a coherent environment the problem of direction finding using arbitrary antenna array geometries always seems to be a multivariate optimisation problem. An estimator derived using suboptimal eigen techniques and optimised using the method of alternating projection (AP) is shown to be superior to the maximum likelihood method.