Sparse Antenna Array Research Articles

Thinning of antenna array via adaptive memetic particle swarm optimization

Massive multiple input multiple output antenna array is crucial for the fifth generation wireless communication. Proper antenna array design can reduce interference among different signals and generate desirable beamforming. Sparse antenna array is able to form narrower beam with lower sidelobe than equally spaced antenna array given the same number of array elements. However, determining the position of elements is non-deterministic polynomial-time hard. To effectively solve such problem, this paper proposes adaptive memetic particle swarm optimization (AMPSO) algorithm. The algorithm adaptively tunes algorithmic parameters of particle swarm optimization (PSO). Moreover, crossover operator is added to enhance local exploiting search information of PSO. Sparse antenna array design is modeled as a minimization by thinning method. It is then tackled by the proposed algorithm. In terms of peak sidelobe level, the AMPSO algorithm shows good performance compared with PSO and genetic algorithm.

Design of a sparse antenna array for radar‐based structural health monitoring of wind turbine blades

The imaging performance of a sparse antenna array depends on the arrangement of the transmitting and receiving elements. In this study, the authors systematically extend the work presented by Caba and Boreman by a constraint optimisation of the Y-shaped antenna arrangement. This will lead to an improved point-spread function with reduced sidelobes. It was found that a 30% improvement of the imaging performance using backprojection techniques could be achieved compared with conventional array designs. The optimised sparse antenna array has been used in a simulation study to evaluate its performance for radar-based structural health monitoring of wind turbine blades. Depending on the damage position, either close to the front or back side of the rotor blade, the localisation error has been quantified as a function of its generally unknown effective relative permittivity.

Direction of arrival tracking for signals with known waveforms based on block least squares techniques

In this paper, we address the problem of tracking DOA of multiple moving targets with known signal source waveforms and unknown gains in the presence of Gaussian noise using a nonuniform linear array. Herein, we make use of the fact that the output of each sensor can be described as a linear regression model whose coefficients each contain a pair of DOA and gain information corresponding to one target. These coefficients are determined by solving a linear least squares (LS) problem and then updated recursively based on a block QR decomposition recursive least squares (QRD-RLS) technique or a block regularized LS technique. Since the coefficients from different sensors have the same amplitude but variable phase information for the same signal, along with simple algebraic manipulations the well-known generalized least squares (GLS) are used to obtain an asymptotically-optimal DOA estimate without requiring a search over a large region of the parameter space. Computer simulations show that the proposed DOA tracking techniques when applied to a sparse antenna array can provide a better tracking performance than some of the existing methods do.

Location and Orientation Optimization for Spatially Stretched Tripole Arrays Based on Compressive Sensing

The design of sparse spatially stretched tripole arrays is an important but also challenging task and this paper proposes for the very first time efficient solutions to this problem. Unlike for the design of traditional sparse antenna arrays, the developed approaches optimise both the dipole locations and orientations. The novelty of the paper consists in formulating these optimisation problems into a form that can be solved by the proposed compressive sensing and Bayesian compressive sensing based approaches. The performance of the developed approaches is validated and it is shown that accurate approximation of a reference response can be achieved with a 67% reduction in the number of dipoles required as compared to an equivalent uniform spatially stretched tripole array, leading to a significant reduction in the cost associated with the resulting arrays.

Compressive sensing based sparse antenna array design for directional modulation

Directional modulation (DM) can be achieved based on uniform linear arrays where the maximum spacing between adjacent antennas is half-wavelength of the frequency of interest in order to avoid spatial aliasing. To exploit the additional degrees of freedom provided in the spatial domain, sparse antenna arrays can be employed for more effective DM. In this study, the spare array design problem in the context of DM is formulated from the viewpoint of compressive sensing (CS), so that it can be solved using standard convex optimisation toolboxes in the CS area. In detail, a common set of active antennas needs to be found for all modulation symbols generating a response close to the desired one. The key to the solution is to realise that group sparsity has to be employed, as a common antenna set cannot be guaranteed if the antenna locations are optimised for each modulation symbol individually. Moreover, two practical scenarios are considered for the proposed design: robust design with model errors and design with practical non-zero-sized antennas, and corresponding solutions are found by modifying the proposed standard solution.

Status of air-shower measurements with sparse radio arrays

This proceeding gives a summary of the current status and open questions of the radio technique for cosmic-ray air showers, assuming that the reader is already familiar with the principles. It includes recent results of selected experiments not present at this conference, e.g., LOPES and TREND. Current radio arrays like AERA or Tunka-Rex have demonstrated that areas of several km^2 can be instrumented for reasonable costs with antenna spacings of the order of 200 m. For the energy of the primary particle such sparse antenna arrays can already compete in absolute accuracy with other precise techniques, like the detection of air-fluorescence or air-Cherenkov light. With further improvements in the antenna calibration, the radio detection might become even more accurate. For the atmospheric depth of the shower maximum, Xmax, currently only the dense array LOFAR features a precision similar to the fluorescence technique, but analysis methods for the radio measurement of Xmax are still under development. Moreover, the combination of radio and muon measurements is expected to increase the accuracy of the mass composition, and this around-the-clock recording is not limited to clear nights as are the light-detection methods. Consequently, radio antennas will be a valuable add-on for any air shower array targeting the energy range above 100 PeV.

Evaluating Spatial Resolution and Channel Capacity of Sparse Cylindrical Arrays for Massive MIMO

How to design antenna arrays plays an important role in wireless communications, especially when there are hundreds of antennas. In massive multiple-input and multiple-output (MIMO), if the number of antennas and RF chains are increasing, the channel capacity and transmission efficiency could be obviously improved as well. Since in massive MIMO, antennas at the base station (BS) usually scale up greater than 100, the complexity and hardware requirement of the system are also increased. Many studies about massive MIMO are focused on the analysis of channel capacity, precoding, and so on, and very few are about the sparse antenna array deployment. Based on the sparse linear array structures as indicated by previous studies, three new arrays, namely co-prime cylindrical array (CCA), nested cylindrical array (NCA), and sparse nested cylindrical array (SNCA), are proposed, which are based on co-prime linear array, nested linear array, and sparse circular array, respectively. Compared with the traditional uniform cylindrical array (UCA), the proposed arrays vastly reduce the number of antennas used at the BS. In addition, the performance of spatial resolution and channel capacity of CCA, NCA, and SNCA are discussed in detail. The results show that our proposed sparse cylindrical arrays can obtain a higher resolution with much fewer antennas. Besides, the uplink channel capacity of all the three sparse cylindrical arrays is larger than the UCA with the same number of antennas at the BS.

A Hybrid Technique Using Combinatorial Cyclic Difference Sets and Binomial Amplitude Tapering for Linear Sparse Array Antenna Design

Reducing system complexity and cost in synthesizing a sparse array antenna design is a challenging task for practical communication systems, such as radar systems and space communication. In this paper, a hybrid technique to synthesize a linear sparse array antenna design is described. This technique is developed using two methods. The first method is a combinatorial approach that applies cyclic difference sets (CDS) integers to significantly reduce the number of antenna elements. The approach and procedure used to apply the new CDS method to configure a linear sparse array, with significant reduction of the spatial antenna dimension, is described. The second method, applied to the array result of the first method, is amplitude tapering using a binomial array approach to reduce the sidelobes level (SLL). The simulation and measurement results of the sample sparse array design showed that the SLL was reduced in comparison to the sparse array design using only the combinatorial CDS method.

КОЭФФИЦИЕНТ НАПРАВЛЕННОГО ДЕЙСТВИЯ АНТЕННЫХ РЕШЕТОК

PACS number: 07.57.-c Purpose: Theoretical investigation of directive gains of linear and planar antenna arrays depending on the distance between radiators and wavelength. Design/methodology/approach: Computing methods in applied mathematics in MathCad were used to calculate the twofold integrals of the radiation pattern over power throughout the whole space observed, defining the directivity in the most general terms. Patterns of radiators, i. e. elements of antenna arrays, are specified by mathematical models. The calculation accounts for the subintegral fast oscillating function. Findings: Calculations and analysis of a directive gain according to the number of radiators and distances between them in fractions of wavelength are made. It is shown that at the ratio of distance between radiators to wave-length being d/λ =0.5 the directivity of array of isotropic radiators is 1.5N², N – number of radiators. When increasing the d/λ to 0.65÷0.97 the directivity increases according to the law close to the linear one up to the maximum possible value for the specified number of radiators. With the increase of d/λ to the values greater than one, the directivity is significantly reduced (the “blinding” effect of non-phased antenna arrays) and its dependence with the growth of d/λ is decaying and oscillating in character. By that, the transfer function of antenna arrays has some vital difference from the transfer function of continuous antennas. Conclusions: Antenna arrays distort the waveform and spectrum of radiated and received signals as a result of irregular changes of their directivity depending on wavelength. The detected “blinding” effect of non-phased antenna arrays of large electrical dimensions must be taken into account in wideband and superwideband radio-electronics systems, especially in radio astronomy, telecommunications systems and superwideband radar. Keywords: antenna arrays, directivity, pattern, weakly directed radiators, numerical analysis Manuscript submitted 05.07.2016 Radio phys. radio astron. 2016, 21(4): 285-297 REFERENCES 1. GOROBETS, N. N. and GOROBETS, Yu. N., 1990. Computer analysis of the directional characteristics of antenna arrays. In: Computer methods of research of problems of the theory and technology of transmission of digital signals by radio : Conf Proc. Moscow: Radio i Svyaz' Publ., pp. 47–48 (in Russian). 2. FELD, Y. N. and BENENSON, L. S.,1955. Centimeter-wavelengthand microwave antennas. Moscow: N. E. Zhukovsky Academy Publ. (in Russian). 3. SHUBARIN, Y. V., 1960. Microwave Antennas . Kharkiv, Ukraine: Kharkiv State University Publ. (in Russian). 4. MINKOVICH, B. M. and YAKOVLEV, V. P., 1969. Theory of Antenna Synthesis . Moscow: Sovetskoe Radio Publ. (in Russian). 5. MARKOV, G. T. and SAZONOV, D. M., 1975. Antennas. Moscow: Energiya Publ. (in Russian). 6. GOROBETS, N. N. and BULGAKOVA, A. A., 2008. Sparse antenna array patterns. The Journal of V. N. Karazin Kharkiv National University, series Radiophysics and Electronics. vol. 834, is. 13, pp. 89–94 (in Russian). 7. MOTLOHOV, V. V., 1990. Antenna facilities . Moscow:USSR Ministry of Defense Publ. (in Russian). 8. KONOVALENKO, A. A., TOKARSKY, P. L. and YERIN, S. N., 2013. Effective Area and Directional Patterns of Antenna Array Operating in Ultra Wideband Signals Receiving Mode. Radio Phys. Radio Astron. vol. 18, no. 3, pp. 257–264 (in Russian). 9. CHAPLIN, A. F., 1987. Analysis and synthesis of antenna arrays. Lviv, Ukrain: Vishcha Shkola Publ. (in Russian). 10. HANSEN, R. C., 2009. Phased Array Antennas . 2nd ed. New York: Wiley.DOI: https://doi.org/10.1002/9780470529188 11. SHULGA, V. M., LYTVYNENKO, L. M. and MYSHENKO, V. V., 2005. Some Development Stages in the Millimeter Wavelength Radioastronomy Observations at the Institute of Radio Astronomy NAS-Ukraine. Radio Phys. Radio Astron. vol. 10, special is., pp. S45–S53 (in Russian).

Maximally Sparse, Steerable, and Nonsuperdirective Array Antennas via Convex Optimizations

Achieving the minimum number of radiating elements in the active electronically scanned array synthesis represents a key problem in those applications where the power consumption, the weight, and the hardware/software complexity of the radiating system have a strong impact on the system cost. In this paper, a new method for the synthesis of planar, nonsuperdirective, maximally sparse, and steerable arrays is proposed and tested on several benchmarks available in the open literature. The method optimizes simultaneously the weight coefficients and sensor positions of a planar array without using global optimization schemes, properly exploiting convex optimization based algorithms. The resulting arrays are able to radiate a steerable beam pattern, satisfying a prescribed power mask and avoid to constraint the fitting of any a priori assigned reference field pattern. Several tests are presented to show the high efficiency in achieving the desired steerable radiation pattern with the minimum number of antenna elements.

Reducing the number of elements in a pattern reconfigurable antenna array by the multi‐task learning

The synthesis of pattern reconfigurable antenna array with as few elements as possible can find wide applications in radar tracking, biomedical imaging, satellite and ground communications, and remote sensing applications. In this study, an efficient method for multi-task learning (MTL) is exploited to the design of sparse pattern reconfigurable antenna array. Toward this end, the design of sparse and pattern reconfigurable antenna array is reformulated as an equivalent problem of multi-matrices linear regression and iterative shrinkage threshold method for MTL is utilised to obtain jointly optimal design of positions and the excitations of the radiating elements for multi-pattern synthesis, in which compromise between the array sparseness and pattern matching is achieved. Some numerical simulations are presented to assess the efficiency of the proposed method and the synthesis performance comparisons with matrix pencil method and genetic algorithm are also performed to demonstrate the superiority of the proposed algorithm over traditional algorithm in this literature.

Random Sparse Coherent Antenna Arrays, Focused in the Near Radiated Field

Random Sparse Coherent Antenna Arrays, Focused in the Near Radiated Field

Sparse Antenna Array Design for MIMO Radar Using Multiobjective Differential Evolution

A two-stage design approach is proposed to address the sparse antenna array design for multiple-input multiple-output radar. In the first stage, the cyclic algorithm (CA) is used to establish a covariance matrix that satisfies the beam pattern approximation for a full array. In the second stage, a sparse antenna array with a beam pattern is designed to approximate the desired beam pattern. This paper focuses on the second stage. The optimization problem for the sparse antenna array design aimed at beam pattern synthesis is formulated, where the peak side lobe (PSL) is weakly constrained by the mean squared error. To solve this optimization problem, the differential evolution (DE) algorithm with multistrategy is introduced and PSL suppression is treated as an inequality constraint. However, in doing so, a new multiobjective optimization problem is created. To address this new problem, a multiobjective differential evolution algorithm based on Pareto technique is proposed. Numerical examples are provided to demonstrate the advantages of the proposed approach over state-of-the-art methods, including DE and genetic algorithm.

Ultrasonic testing on a singly reflected beam using sparse antenna arrays and 3D echo-signal processing

Testing of welded joints in the main shutoff valves (MSVs) of the first circuit of a ВВЭР-440 reactor plant is impeded due to the high structural-noise level and the necessity of using pulses that are singly reflected from the tilted bottom of a branch pipe. Testing on a longitudinal wave leads to the appearance of false reflections, which are formed by pulses at a transverse wave, in the reconstructed image. Since the amplitude of false reflections can be commensurable with the amplitude of reflections that were obtained at longitudinal waves, the analysis of such images may be hampered. To increase the quality of an image, it is proposed to record echo signals using sparse antenna arrays and use 3D processing of echo signals. Numerical and model experiments showed that this approach increases the frontal resolution in the additional plane by several times and reduces the amplitude of false reflections, thus making it possible to increase the sensitivity and reliability of expert ultrasonic testing of the principal shutoff valve.

Sector nulling in planar irregular sub‐arrayed sparse array antennas

This study concerns wide angular sector (higher order) null synthesis in planar irregular sparse antenna arrays when aperture distributed sub-arrays are used to reduce the computational load. A hybrid optimisation tool has been used to find array element excitations to achieve as low as possible sector nulls for the desired sector width. Performance comparisons have been made for three sub-array configurations based on the obtained numerical results. Various interference jamming scenarios have been considered including single and dual sectors for single-dimensional ( θ ) (1D) and two-dimensional ( θ , ϕ) (2D) nulls. The proposed optimisation scheme has shown to be successful for the synthesis of 1D and 2D sector nulls with depths as low as −100 dB for the given configuration with reduced computational time when compared with the full array. The comparison of achieved null depths for different sub-array sizes and convergence time has also been presented and discussed.

Antenna array layout optimization of collaborative passive millimeter-wave imaging system

Based on the advantages of phased array and synthetic aperture imaging method in passive millimeter-wave imaging,a collaborative passive millimeter-wave imaging system was developed for real-time and high resolution imaging in human security application. In the horizontal orientation,by applying annealing algorithm,different aperture horn antennas were determined for the improvement of the phased array performance,which was generally compared with the maximum main beam effective and most smoothable sidelobe level. In vertical orientation,the synthetic aperture,namely,the sparse antenna array was designed by the criterion of the most uniform redundant baseline,while baseline absence should be avoided. Finally,simulation results reveal that with the optimized antenna array the requirement of increasing singal-to-noise ratio( SNR)in power measurement in the collaborative passive imaging system can be fulfilled.

Wideband Grating-Lobe Suppression by Rotation of the Phased Array Stations in the SKA Low-Frequency Sparse Aperture Array

A simple cost-effective technique of wideband grating-lobe (GL) suppression by rotation of the phased array antennas is developed for application in a system of low-frequency sparse aperture array (LF-SAA) antennas of the square kilometer array (SKA) radio-telescope. The technique implies using of equal sparse planar circular antennas with the well-tried square lattice (SqL) distribution of the station antenna array sensors, which is known as the best in terms of production costs and maintenance charges. The peak levels of residual GLs in the fringe pattern of most pairs of the rotated antenna array stations do not exceed value of -17 dB over frequencies ranged from 70 to 450 MHz in the case of uniform antenna array element weighting, whereas the maximum levels of residual GLs are reduced to -25 dB when the Hamming weight tapering is applied.

Local‐DoFs of Airborne Radar Clutter for Reduced‐Dimensional STAP with Sparse Antenna Array

Space-time adaptive processing (STAP) technique can mitigate airborne radar clutter and detect moving targets effectively. Based on adaptive radar theory, the Degrees-of-freedom (DoF) of a STAP processor should be larger than that of the received clutter. The local-DoFs of clutter for Reduced-dimensional STAP (RDSTAP) methods with sparse linear array are studied. The proposed formulas show that the local-DoFs of clutter can be estimated as the product of the equivalent clutter bandwidth with the equivalent sampling interval.

Spectrum reconstruction and the performance analysis for multichannel bidirectional SAR

Single-channel bidirectional synthetic aperture radar (BiDi-SAR) systems require the pulse repetition frequency (PRF) to be cautiously designed. Firstly, it should be higher than the total bandwidth of the two Doppler subbands; secondly, it should be carefully selected so that the two Doppler subbands are properly located. We introduce multichannel BiDi-SAR imaging mode to realize bidirectional high resolution wide swath (HRWS) imaging. Acquisition geometry of multichannel BiDi-SAR is interpreted. Doppler spectrum of BiDi-SAR consists of two subbands with limited bandwidth. Based on a prior knowledge about the location of the Doppler subbands, we derive the method for separating the aliased Doppler spectra for general PRFs. Then, we analyze the reconstruction performance in terms of azimuth ambiguity to signal ratio (AASR) and signal to noise ratio (SNR). Besides, we propose to use a properly designed sparse array antenna to improve the azimuth ambiguity performance. Validity of the signal processing method is verified by simulation results.

Design of Maximally Sparse Antenna Arrays in the Presence of Mutual Coupling

An optimization framework is proposed that combines electromagnetic field simulations with an iterative ${\ell _1}$ -norm minimization procedure to synthesize optimally sparse antenna arrays. The proposed approach overcomes the limitation of design methodologies that assume idealized antenna elements employing equal (isolated or isotropic) element patterns, as these yield suboptimal solutions when the antenna mutual coupling effects cannot be ignored. The latter is demonstrated for arrays of relatively strongly coupled dipole radiators.