Linear Dipole Array Research Articles

Antenna pattern analysis using S‐parameters for strongly coupled dipole arrays

AbstractAn antenna pattern and efficiency estimation procedure for uniform linear dipole arrays with large mutual coupling is presented. The feed currents for each dipole elements are extracted from S‐parameters with antenna arrays being treated as N‐port circuit networks. The dipole current is assumed to maintain a sinusoidal distribution even in array environments. The estimated patterns for E‐plane and H‐plane linear array examples as well as a Yagi‐Uda sample confirm the validity of the proposed procedure.

The Synthesis of a Magneto-Electric Dipole Linear Array Antenna Using the Element-Level Pattern Diversity (ELPD) Technique

The synthesis of a magneto-electric (ME) dipole linear array using an element-level pattern diversity (ELPD) technique is presented in this letter. This linear array with fewer elements, simple structure, and feed network can achieve similar performance of a conventional two-dimensional array because of the application of both the ELPD technique and the ME dipole element. The synthesis of the E-plane radiation pattern is achieved by the superposition of the radiation patterns of different modes with certain weighting, while the H-plane radiation pattern is achieved mainly by array factor with the same weighting. The configuration of the array is given. A three-element ME dipole array with the ELPD technique to obtain equal beamwidths in E- and H-plane is presented as an example to show the design and synthesis procedure. The measured 12.5% impedance bandwidth at a center frequency of 2.4 GHz with | S 11|<–10 dB and stable radiation patterns are achieved. The measured gain is 11.2 dBi at the frequency of 2.4 GHz. The results validate the proposed array and its synthesis procedure.

Shaped Power Pattern Synthesis of a Linear Dipole Array by Element Rotation and Phase Optimization Using Dynamic Differential Evolution

A novel strategy for synthesizing shaped power pattern by using element rotation and phase optimization for a linear dipole array is presented. Element rotation can be considered as an array amplitude weighting technique, and it provides additional degrees of freedom in the pattern synthesis, but potentially increases the cross-polarization level (XPL). In order to obtain a desired copolarized shaped pattern with both the sidelobe level and XPL constrained, we simultaneously optimize all the rotation angles and excitation phases of all the dipole elements by applying the dynamic differential evolution algorithm. Two experiments for synthesizing flat-top and cosecant-squared patterns are conducted to validate the effectiveness and advantages of the proposed strategy.

Wideband Dual-Polarized Linear Array of Tightly Coupled Elements

Previous studies on tightly coupled dipole arrays (TCDAs) are mainly focused on 2-D phased arrays, where very wide bandwidth can be achieved as compared to 1-D TCDAs. Moreover, for the dual-polarized case, the interelement coupling is not sufficient in the polarization along the transverse direction of linear array, which leads to a much narrower bandwidth. In this communication, a wideband dual-polarized tightly coupled dipole linear array (TCDLA) is proposed. A novel vertical parasitic superstrate layer is employed in the dual-polarized linear array to compensate the impedance variation in beam scanning cases. As compared to traditional wide-angle impedance matching layer composed of layered dielectric sheets, the vertical parasitic superstrate layer greatly reduces the weight of the array. Simulation results show that the TCDLA achieves 5:1 bandwidth and 4:1 bandwidth in the vertical polarization and horizontal polarization, respectively, for VSWR $1 \times 26$ linear array is fabricated and measured. Good agreement is achieved between measured and simulation results.

Link-Level Analysis of a Multiservice Indoor Distributed Antenna System [Wireless Corner

In this article, the link-level performance of a multiservice indoor distributed antenna system (MS-IDAS) in an indoor-hotspot scenario is studied. A low-profile broadband antenna is proposed as the access point (AP) antenna, and then it is used as an identical array element for constructing two-and three-port multipleinput, and multiple-output (MIMO) antennas. The proposed MS-IDAS antenna covers various IEEE 802.11 standards within 2-6 GHz, and its link-level simulations are performed at 5 GHz for the 802.11n protocol. The error-rate performances of the three-element MIMO antenna is analyzed in WINNER indoor scenarios by using simulated-channelimpulse response (CIR). In a typical indoor-hotspot room with dimensions of 20 m x 20 m x 10 m, the wallmounted MS-IDAS antenna shows better coverage than the ceilingmounted case. In addition, the proposed MIMO antenna outperforms a uniform linear-dipole array with the same interelement distance in terms of error-rate performance.

Spatial domain indirect holographic technique for antenna near‐field phaseless measurements

AbstractA spatial domain formulation of an indirect holographic technique, useful for antenna near‐field phase retrieval, is presented in this paper. The proposed approach is based on the adoption of three synthetic reference signals, giving three sets of amplitude‐only near‐field data. These are directly processed in the spatial domain to accurately retrieve the near‐field phase, from which the antenna radiation features can be subsequently computed. Despite the standard indirect holographic approach, no data processing is required in the spectral (Fourier transform) domain, thus completely avoiding the problem of spectrum overlapping which limits the accuracy of standard method. The effectiveness of the proposed technique is demonstrated by a numerical test on a linear dipole array, as well as by experimental results on a ridged‐horn antenna.

Research on Genetic Algorithm of Antenna Arrays Beam Shaping with Side Lobe Suppression

Excitation optimization algorithm based on Genetic Algorithm (GA) is mainly used to solve the excitation problems of array antenna beam shaping. When optimizing the excitation of array antenna by traditional genetic algorithm, the beam of array antenna is synthesized by radiation shape of elements in antenna array, and then the results will be compared with the target pattern. After several operations, the excitation will meet the deign requirements. However, in traditional genetic algorithm, neglected suppression of side lobe leads to an unsatisfactory high level side lobe. In this paper, a new method of beam synthesizing by peak beam of array antenna is proposed. By comparing the shape of synthesized beam with target beam and combining with traditional GA, the synthesized beam matching the target beam with low side lobe will be obtained. Taking a 16 elements X band micro-trip dipole linear array antenna as an example, the results of simulation show that array antenna has high level side lobe suppression at about -27.5 dBc using the method proposed in this paper, which is much better than -19 dBc side lobe suppression using traditional GA.

Beam Pattern Analysis of Antenna Array on Complex Platform Using AEP Method Based on Hybrid UTD-ACGF Technique

For accurate beam analysis of a radiating antenna array on a complex platform, the mutual coupling and platform scattering effects are important. We proposed a beam pattern analysis method for an antenna array on a complex platform, which combines the active element pattern method of the receiving mode and hybrid geometrical theory of diffraction antenna current Green’s function technique. This proposed method clearly and mathematically divides the beam pattern of the antenna array on a complex platform into mutual coupling and platform scattering components. For a 12 linear dipole array embedded in a complex aircraft, analyses of the beam pattern and boresight error using the proposed method were verified with the method of moment results, which were simulated with FEKO. With reasonably good accuracy, the proposed method can efficiently analyze a beam pattern reflecting the mutual coupling effect and the platform scattering effect. Additionally, convex optimization with the proposed method is simply applied to synthesize the compensated beam pattern.

Controllable Terahertz Radiation from a Linear-Dipole Array Formed by a Two-Color Laser Filament in Air.

We demonstrate effective control on the carrier-envelope phase and angular distribution as well as the peak intensity of a nearly single-cycle terahertz pulse emitted from a laser filament formed by two-color, the fundamental and the corresponding second harmonics, femtosecond laser pulses propagating in air. Experimentally, such control has been performed by varying the filament length and the initial phase difference between the two-color laser components. A linear-dipole-array model, including the descriptions of both the generation (via laser field ionization) and propagation of the emitted terahertz pulse, is proposed to present a quantitative interpretation of the observations. Our results contribute to the understanding of terahertz generation in a femtosecond laser filament and suggest a practical way to control the electric field of a terahertz pulse for potential applications.

Cooperative Self-Assembly of Carbazole Derivatives Driven by Multiple Dipole-Dipole Interactions.

Carbazole possessing phenylisoxazoles self-assembled in a cooperative manner in decalin. X-ray crystal structure analysis revealed that the isoxazole dipoles align in a head-to-tail fashion. DFT calculations suggested that the linear array of dipoles induced the polarization of each dipole, leading to an increase in dipole-dipole interactions. This dipole polarization resulted in cooperative assembly.

Analysis of a Uniform Linear Broadside Dipole Antenna Array Operating at 1.8 GHz for Use in GSM Application.

A uniform broadside array antenna is the arrangement of equally spaced and equal&#x0D; current amplitude excitation of identical antennas, which are placed along the axis&#x0D; perpendicular to the direction of maximum radiation. The overall radiation pattern of an&#x0D; array is determined by array factor combined with the radiation pattern of the antenna&#x0D; element. The number of the elements and their spacing may produce the diverse radiation&#x0D; properties. In this work the impact of these two factors on the radiation characteristics of&#x0D; a uniform linear broadside dipole array were analyzed using the 4NEC2 simulation&#x0D; software. The spacing between the elements varied from 0.1λ to 2λ in steps of 0.02λ for&#x0D; a number of elements up to 10 elements. For GSM application at 1.8GHz frequency the&#x0D; best configuration to achieve the required gain of 13.8dBi was 7-elements with 0.88λ&#x0D; spacing.

Coupling Characterization of a Linear Dipole Array to Improve Direction-of-Arrival Estimation

The reciprocity theorem is applied to account for the electromagnetic coupling among antennas in a linear dipole array, in the presence of multiple incident plane waves. By utilizing the direction-dependent coupling information, the direction-of-arrivals of the incident waves can be estimated more accurately by using the conventional ESPRIT (estimation of signal parameter via rotational invariance technique). Different coupling compensation methods in the literatures are compared to validate this method, and multiple incident waves of both uncorrelated and coherent nature are also simulated.

Cambios del patrón de radiación en arreglos lineales de dipolos de microcinta a 2,4 GHz en presencia de elementos parásitos

En este artículo se presenta uno de los resultados de la investigación realizada para estudiar los cambios producidos en los parámetros de impedancia de entrada y patrón de radiación de los sistemas radiantes cuando son sometidos a la presencia de elementos parásitos. Específicamente, se utilizan arreglos lineales de dipolos de microcinta y se escoge como parámetro de estudio el patrón de radiación; el parámetro de impedancia de entrada será presentado en otra publicación. Para su estudio, el sistema es modelado mediante técnicas numéricas con la ayuda del método de los momentos, en la conformación de la malla del arreglo se utiliza la función base propuesta por Rao-Wilton y Glisson. El modelo es simulado con la herramienta Matlab®, se determina el patrón de radiación para un dipolo tipo parche y para un arreglo de estos elementos; se ubican elementos parásitos (dipolos) a diferentes distancias del dipolo y del arreglo original y se calculan nuevamente los patrones de radiación, los cuales son comparado con los inicialmente encontrados. Finalmente, se presentan los resultados y se evidencia la ventaja que tienen estos estudios para la manipulación del patrón de radiación en sistemas radiantes. Adicionalmente, se evidencia en el presente estudio la presencia de un elemento de simetría, lo cual permite disminuir en un alto porcentaje las simulaciones, ya que el efecto producido por los elementos parásitos ubicados a un lado del arreglo de dipolos es similar al efecto que se produce cuando se ubican los elementos parásitos al lado opuesto.

Directivity Estimations for Short Dipole Antenna Arrays Using Radial Basis Function Neural Networks

The role of directivity is very important in the operation of an array as it gives a measure of the effectiveness of the array in pointing the radiations in a specific direction. Traditional methods used for the computation of directivity are although effective but may be time consuming. Artificial neural networks (ANNs) do not require the complex mathematical procedures and are therefore faster. Being nonlinear in nature, ANNs adapt to the nonlinear behavior of antenna arrays easily. In this letter, directivity estimations for the uniform linear arrays of collinear short dipoles and parallel short dipoles, using radial basis function neural networks (RBF-NNs) have been presented. The algorithm has also been applied for a planar array with short dipoles. The robustness of the method has been tested by evaluating its performance for noisy data conditions. The highlight features of the study are the accuracy and speed shown by the method in estimating results for the unseen inputs even in noisy data conditions.

Optimization of Linear Dipole Antenna Array for Sidelobe Reduction and Improved Directivity using APSO algorithm

Design of non-uniformly spaced linear array of dipoles is presented. Array synthesis is done by controlling the appropriate excitation amplitudes and element spacing to get the radiation patterns with reduced sidelobe level (SLL) and improved beam width. The objective of this work is to generate synthesized patterns with low sidelobe level and to compensate the coupling effect with a low prefixed dynamic range ratio for non-uniformly spaced array. The excitation amplitude distribution and position of individual array elements are determined. The patterns of dipole elements are compared with those of the isotropic elements. Numerical results show the effectiveness of the algorithm for the design of the linear array.

Comparative Studies on Generation of Stair Step Radiation Patterns

Antenna array synthesis is usually done by controlling amplitude and phase levels or element spacing functions of the array to get the desired characteristics of the radiation pattern. In this paper, design of equispaced linear array of dipoles is presented. A new amplitude distribution is proposed for generation of stair step patterns with zero phase. These patterns are produced from dipole elements using Fourier transform method. The goal of the work is to compensate mutual coupling effects of a linear dipole array. The computed patterns are compared with those of the isotropic elements for different number of elements. The deviation in the patterns of array of isotropic radiators and the array of practical element is found to be minimum. These patterns are used to identify multiple targets moving in different altitudes and different angular regions.

Scattering Analysis of an Unequal-Length Dipole Array in the Presence of Mutual Coupling [Antenna Applications Corner

The scattering behavior of a phased array depends on its design parameters, feeding network, and the platform over which it is mounted. In this paper, the total scattered field from an unequal-length dipole array is analyzed towards controlling the radar cross section (RCS) of the array. The mutual-coupling effect between the dipole elements is taken into account. The RCS of a non-skewed linear dipole array is analytically estimated by computing the signal reflections at each level of the antenna system. The closed-form formulation for the RCS estimation of the dipole array is separately presented for both series and parallel feeding networks. An attempt has been made to explain the variations observed in the RCS patterns corresponding to different configurations of unequal length dipole arrays arbitrarily arranged. The effects on the array's RCS of optimizing the lengths of the dipoles and of other parameters are discussed. It is shown that the appropriate choice of the lengths of the dipoles can contribute towards the reduction of the array's RCS.

Adaptive nulling of a linear dipole array in the presence of mutual coupling

This article proposes a novel mutual impedance matrix model for compensating mutual coupling effects in adaptive array with application to adaptive nulling of interference signals. In the new method, extreme care has been taken into account for both self impedance and mutual impedance, relating to the mutual coupling effects. Numerical simulation results demonstrate the robustness and capability of this technique. By using the new method, it is found that both the accuracy of the positioning and depth of the nulls are significantly improved. Performance comparisons of the new methodology and several other previous techniques via a number of simulation are presented. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:30–38, 2014.

Scattering Analysis of a Compact Dipole Array with Series and Parallel Feed Network including Mutual Coupling Effect

The current focus in defense arena is towards the stealth technology with an emphasis to control the radar cross-section (RCS). The scattering from the antennas mounted over the platform is of prime importance especially for a low-observable aerospace vehicle. This paper presents the analysis of the scattering cross section of a uniformly spaced linear dipole array. Two types of feed networks, that is, series and parallel feed networks, are considered. The total RCS of phased array with either kind of feed network is obtained by following the signal as it enters through the aperture and travels through the feed network. The RCS estimation of array is done including the mutual coupling effect between the dipole elements in three configurations, that is, side-by-side, collinear, and parallel-in-echelon. The results presented can be useful while designing a phased array with optimum performance towards low observability.

Design of a Low Sidelobe Time Modulated Linear Array With Uniform Amplitude and Sub-Sectional Optimized Time Steps

A novel approach for the design of low sidelobe time modulated linear arrays (TMLAs) with uniform amplitude excitations and suppressed sidebands is presented. The approach is based on the division of the time modulation period <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">Tp</i> into several time steps with variable lengths. In each time step, the switch-on and switch-off times are optimized via the differential evolution (DE) algorithm. As compared to previous approaches, such as the variable aperture sizes (VAS), pulse shifting, and binary optimized time sequences (BOTS), the proposed approach has more flexibility in the design of time sequences in TMLAs. Numerical results show that a -30 dB sidelobe pattern with uniform excitations can be synthesized, while the sideband level (SBL) is suppressed to -27.8 dB. Experimental results based on a 16-element printed dipole linear array agree with the theoretical results, thus verified the proposed approach.