Antenna Array Elements Research Articles

Experimental Investigation of Millimeter-Wave MIMO Channel Characteristics in Tunnel

A 28 GHz millimeter-wave (mm-wave) propagation measurement campaign was performed to predict the multiple-input multiple-output (MIMO) channel performance in a tunnel environment. Two kinds of polarization configurations were studied in this paper. In order to overcome the serious path loss (PL) of mm-wave propagation, a high gain directional horn antenna was used in the measurements of tunnel environment. The measurement results and simulation results at same specific locations are compared. The result of comparison indicates that the simulation model matches the measurement well. Then the MIMO capacity at other locations of the tunnel can be predicted by the simulation model. Further-more, it is inferred that the antenna array elements of horizontally polarized configuration have higher capacity than the vertically polarized under the constant signal-to-noise ratio (SNR).

The method of array antenna constructive synthesis on the basis of neural network approach

The method to decision constructive synthesis of array antennas was conducted. The method usefull when antenna elements can be in discreste states (for example: active element, passive element, excluded item, active element with discrete nominal of output power e.t.c). The method is based on neural network approach. The structure of a neural network consist of a classifying neural network and several approximating neural networks is substantiated. Input signals correspond to phase centers of array antenna elements. Number of output signals in classifying part is equal to discrete status of antenna element. Each approximating part of network has one output signal wich correspond to continious meaning. Separate parts of network preliminary learning with error back propagation method. The genetic algorithm of neural network learning with limited number of training coefficients is proposed. Examples of solving problems of constructive synthesis, with different indicators of the quality of neural network training are given.

Development of an Algorithm for Optimizing Array Antenna Elements for Cellular Networks Using Evolutionary Computation

This research article published by International Journal of Digital Information and Wireless Communications, Vol. 9, No. 2, 2019

Design of a wide-angle scanning tightly coupled dipole array element

The paper proposes a novel tightly coupled dipole array antenna element design, and combines the equivalent circuit to analyze and optimize antenna parameters. The design introduces frequency selective surface placed above the antenna aperture to replace the traditional dielectric superstrate for wideband and wide-angle impedance matching. The balun employs microstrip to coplanar parallel two-wire transition structure to achieve balanced feed and impedance transformation. A prototype is simulated and the results show that the design provides a 3:1 (from 2 GHz to 6 GHz) bandwidth while scanning to 80° in E-plane and scanning to 45° in H-plane, with an active VSWR<3. Besides, the cross-polarization isolation of the array at broadside is kept at 25 dB, but the antenna gain is reduced due to the loss of the resistive FSS. The antenna has a simple and compact structure, easy to fabricate, thus realizes miniaturization of a tightly coupled array.

Eight Element Multiple-Input Multiple-Output (MIMO) Antenna for 5G Mobile Applications

This work presents a systematic design of high performance eight element antenna array for a 5G mobile terminal operating at 2.6/3.5 GHz bands. The proposed eight element slot antenna array based on unit monopole slot antenna embedded in the metal casing or ground resonates at fundamental mode at 2.6 GHz. The antenna array is developed from four antennas (open-end slot antenna) etched near to the corner edges of the printed circuited board with supported pairs of vertically mounted slot antennas in middle section of the long edge ground plane. This combination of the antenna elements provided pattern diversity and enabled the smartphone in the reception of the signal in a different direction. The impedance bandwidth based on -10 dB return loss criteria cover from 2.4 GHz to 3.6 GHz includes the two allocated bands of (2400 MHz to 2600 MHz) and (3400 MHz to 3600 MHz) for 5G cellular communication systems. The vital MIMO performance measures as envelope correlation coefficient or ECC is less than 0.2 for any two antenna array meeting the required standard of less than 0.5 alongside the mean effective gain or MEG ratio of any two antenna meeting the required standard of less than 3 dB for power balance and optimal diversity performance. As modern smartphone demand desires slim handsets, the after mentioned compact multiple antenna structure can be easily implemented for the future smartphones as it utilizes the conductive sheet or chassis and the middle vertically mounted antenna do not use the additional space of the chassis or ground. The customer hand or human hand effect on the multiple antenna array to mimic the use of mobile phone customer is also studied. The maximum MIMO Channel capacity based on measured result is 34.25bps/Hz and is about 3 times of 2 × 2 MIMO operations.

UWB four elements antenna array

AbstractIn this work, a planar UWB four elements antenna array with and without notch filter is designed. The feeding system of the array is an UWB four branch multiple segment power divider/combiner. Each branch has a three segments impedance transformer. Measurements show that the array works well within the band 3.1 to 10.6 with S11 lower than −10 dB. It is shown that the maximum gain varies with the operating frequency having a value of 8 to 12.3 dB and that it is higher than the gain of the single element.

Faulty elements diagnosis of phased array antennas using a generative adversarial learning-based stacked denoising sparse autoencoder

ABSTRACTDiagnosis of faulty elements in a linear phased array antenna is of great importance in the wireless communication field which has been received increasing attention. As a result of element or elements failure in the linear phased array antennas, the whole radiation pattern will suffer from high side lobe levels, wide bandwidth and unexpected nulls. To this end, we suggest a novel approach by combining the generative adversarial learning and the stacked denoising sparse autoencoder to determine the location of the faulty elements in antennas. The suggested approach can learn discriminative features from radiation pattern images adaptively and automatically with less expert knowledge. Meanwhile, the suggested approach is able to overcome the strong noise, the high dimensional size of the radiation pattern and the small fault samples. In this regard, the suggested approach possesses superiority in discriminant capability in contrast to the existing related approaches.

DoA estimation of highly correlated stochastic sources using neural model

ABSTRACTMultiLayer perceptron (MLP)-based neural model for an efficient 1D DoA estimation of highly correlated stochastic EM sources is proposed. Model extracts this information from a spatial correlation matrix obtained by sampling stochastic signals by a receiving antenna array. Algorithm for optimal selection of correlation matrix elements from the upper triangle of the matrix is suggested to reduce the number of antenna array elements needed to obtain an accurate neural model with relatively simple architecture. This approach is verified by determining the azimuth position of two sources with the mutual correlation in the range [0.8–0.95] using antenna arrays with different number of elements.

A compact low-side lobes three-layer array antenna for X-band applications

This paper proposes a low-side lobe lightweight array antenna for X-band applications with center frequency of 9.5 GHz. The proposed array antenna, being composed of 144 (12 × 12) single antenna elements, is designed in a three-layer configuration with total size of the 30 cm × 30 cm. Technically speaking, it is composed of two substrates and three conductive layers on the top, bottom, and between the substrate layers. The main part of the feeding network is located on the bottom side of the antenna structure while the radiating patches are printed on the top side. The ground plane is placed in the middle layer between the two substrates. Isolation of the feed network from the radiating patches, which is realized by the embedded ground plane, yields cross-polarization and side lobe levels (SLLs) reduction. Besides, the feeding system excites the top side patches by connecting to them through vias. Moreover, 1–6 power dividers in the feeding system are connected to each other to form the complete 144-element array configuration. Adopting this technique provides easy development of a planar 2n × 2n element array antenna. To achieve low side lobes, the Dolph-Chebyshev amplitude taper coefficients are used in the design process.

Calibration of Phase Shifters on Basis of Vector-Sum Signals

Attenuators and phase shifters which are the circuits for amplitude-phase distribution control are key elements of antenna arrays. Dispersion of technology parameters results in deviation of the characteristics of integral circuits from rated values that requires application of the techniques for this effect compensation. In this paper there are considered the methods for development and calibration of the circuits in a basis of vector-sum signals allowing to modify both amplitude and phase of input high-frequency signal. It is proposed the method of calibration on a basis of interpolation of measured dependences of absolute value and phase of transfer factor on controlling voltage. Application of proposed method for calibration of vector phase shifter with operating frequency band 2.8–3.2 GHz fabricated with 0.18 mm CMOS allows to provide mean square deviation of phase error is not greater than 0.9°. At that amount of required measurements is 20 times decreased comparing known approach on a basis of measurement of all amplitude-phase states.

Interaction Between Closely Packed Array Antenna Elements Using Meta‐Surface for Applications Such as MIMO Systems and Synthetic Aperture Radars

AbstractThe paper presents a technique to enhance the isolation between adjacent radiating elements that is common in densely packed antenna arrays. Such antennas provide frequency beam‐scanning capability needed in multiple‐input multiple‐output (MIMO) systems and synthetic aperture radars. The method proposed here uses a metamaterial decoupling slab (MTM‐DS), which is located between radiating elements, to suppress mutual coupling between the elements that would otherwise degrade the antenna efficiency and performance in both the transmit and receive mode. The proposed MTM‐DS consists of mirror imaged E‐shaped slits engraved on a microstrip patch with inductive stub. Measured results confirm over 9–11 GHz with no MTM‐DS the average isolation (S12) is −27 dB; however, with MTM‐DS the average isolation improves to −38 dB. With this technique the separation between the radiating element can be reduced to 0.66λ0, where λ0 is free space wavelength at 10 GHz. In addition, with this technique there is 15% improvement in operating bandwidth. At frequencies of high impedance match of 9.95 and 10.63 GHz the gain is 4.52 and 5.40 dBi, respectively. Furthermore, the technique eliminates poor front‐to‐back ratio encountered in other decoupling methods. MTM‐DS is also relatively simple to implement. Assuming adequate space is available between adjacent radiators the MTM‐DS can be fixed retrospectively on existing antenna arrays, which makes the proposed method versatile.

Design and development a wideband SIW based cavity‐backed slot antenna using two symmetrical circular corner perturbations

In this article, a new method to enhance the impedance bandwidth of a square-shaped substrate integrated waveguide (SIW) cavity-backed slot antenna is presented. Using perturbation technique by two corners cuts along two opposite sides of the cavity's diameter, the two degenerate TE120 and TE210 modes of the cavity are separated and a wideband SIW cavity-backed slot antenna is developed. A parametric study is carried out to study the effects of the shape of the perturbation on the radiation performance of the introduced antenna. The proposed antenna is simulated using full-wave software and a prototype of the antenna is fabricated to investigate experimentally. It is shown that the measured results agree well with those obtained by simulation. The measured results show that the designed antenna offers 5.7% fractional impedance bandwidth with a peak gain of 6.4 dBi, while provides a few advantages including low profile, light weight, easy fabrication with low-cost printed circuit board (PCB) and convenient integration with planar circuits. The introduced antenna can be used as a single antenna or as an element of a large antenna array.

Study on isolation improvement between closely‐packed patch antenna arrays based on fractal metamaterial electromagnetic bandgap structures

A decoupling metamaterial (MTM) configuration based on fractal electromagnetic-bandgap (EMBG) structure is shown to significantly enhance isolation between transmitting and receiving antenna elements in a closely-packed patch antenna array. The MTM-EMBG structure is cross-shaped assembly with fractal-shaped slots etched in each arm of the cross. The fractals are composed of four interconnected-`Y-shaped' slots that are separated with an inverted-`T-shaped' slot. The MTM-EMBG structure is placed between the individual patch antennas in a 2 × 2 antenna array. Measured results show the average inter-element isolation improvement in the frequency band of interest is 17, 37 and 17 dB between radiation elements #1 & #2, #1 & #3, and #1 & #4, respectively. With the proposed method there is no need for using metallic-via-holes. The proposed array covers the frequency range of 8-9.25 GHz for X-band applications, which corresponds to a fractional-bandwidth of 14.5%. With the proposed method the edge-to-edge gap between adjacent antenna elements can be reduced to 0.5λ 0 with no degradation in the antenna array's radiation gain pattern. Across the array's operating band, the measured gain varies between 4 and 7 dBi, and the radiation efficiency varies from 74.22 and 88.71%. The proposed method is applicable in the implementation of closely-packed patch antenna arrays used in SAR and MIMO systems.

Concentric Circles and Spiral Configurations for Large Correlator Arrays in Radio Astronomy

Abstract Aperture synthesis arrays are commonly used in radio astronomy to take images of radio point sources, with the planned Square Kilometre Array (SKA) being the most common example. One approach to enhancing the quality of the images is to optimize an antenna array configuration in a possible SKA implementation. An ideal arrangement must ensure optimal configurations to capture a clear image by either decreasing the sidelobe level (SLL) in the l–m domain or increasing the sampled data in the spatial-frequency domain. In this paper a novel configuration is considered to optimize the array by considering all possible observation situations through the positions of the antenna array elements via a mathematical model that we call geometrical method (GM). To demonstrate its efficiency, the technique is applied to developing an optimal configuration for the elements of the Giant Metrewave Radio Telescope (GMRT). The effect of these changes, particularly in the forms of circular and spiral arrangements, is discussed. It is found that a spiral configuration results in fewer overlapping samples than the number of antennas placed along three arms of the GMRT with fewer than 11% and 27% overlapping samples in the snapshot and 6 hr tracking observations, respectively. Finally, the spiral configuration reduces the first SLL from −13.01 dB, using the arms of the current GMRT configuration, to −15.64 dB.

Correction of amplitude-phase field distribution at aperture of deformed large-aperture fixed phased array

On the basis of an analytical review of scientific and technical information sources dedicated to correction of errors in the gainphase distribution of the field on the aperture of the phased antenna array, such errors been caused by correlation of errors in phase quantization by discrete phase shifters, and also caused by disbursement of their characteristics and by failures in a part of the phased antenna array elements, an unresolved problem has been discovered. It is required to correct the amplitudephase distribution errors caused by deformation of the curtain of the large-aperture stationary phased antenna array and resulting in deviation of the radiating elements from their design parameters. A mathematical apparatus of the field distribution electronic correction is being developed together with an algorithm for controlling the radiation pattern of the phased antenna array. The effectiveness of the proposed method for correcting the array pattern distribution on the aperture of the deformed phased antenna array has been evaluated and an option for technical implementation thereof has been proposed.The relevance and novelty of the work is confirmed by the patent for the invention developed on the basis of the studies performed and by the certificate of state registration of the software, which was based upon in the processing of results of the measurements of the deformations in the curtain of the large-aperture phased antenna array.

Design of Hybrid Antenna System for User Terminal Applications

Abstract An eight-element hybrid Smart antenna-MIMO system for user terminal application is proposed in this paper. The hybrid antenna system is based on an eight elements antenna array. When operate with respective feed ports, by using radiation pattern diversity, more than 15 dB isolation among antenna elements can be achieved. After designing the feed networks based on maximum power transmission optimization between the transmit and receive antennas, beam steering performance can be obtained, the eight elements work together as a smart antenna array. The hybrid system has both the advantages of MIMO and smart antenna, and is competitive for future wireless communication applications.

Parameterised codebook design based on channel statistics for efficient multi‐rank MIMO transmission

As the number of antenna elements increases in multiple-input multiple-output (MIMO) systems, an efficient feedback and beamforming strategy becomes more important to achieve the desired bandwidth efficiency required by the next-generation wireless systems. The authors investigate the statistical characteristics of the MIMO channel generated by the three-dimensional spatial channel model to recognise some of the limitations inherent in the existing codebooks adopted by the current third generation partnership project specifications. Such limitations include unnecessary co-phasing combinations for cross-polarised (X-pol) antenna arrays and, in particular, long-term codevector selections, which are not best suited to the channel distributions. In this study, the observed shortcomings are improved by proposing a new multi-rank codebook applicable to the X-pol array of antenna elements supporting up to the quadruple rank. The proposed beamforming codevectors are presented using variable parameters so that they can be adapted to changing channel characteristics. The efficiency of the proposed codebook is further improved by eliminating redundant co-phasing values. The performance of the proposed codebook is evaluated using the TR 36.873 urban macro environment and its effectiveness is demonstrated by quantifying its gain over the existing codebooks.

Study of field distortions introduced by antenna array mobile carrier body

AbstractIn this article was presented a method for optimal location of the “virtual” antenna array elements, based on obtaining a surface map of the same field phase distortion, averaged over the set of frequencies and azimuthal coordinates. This method does not require information about geometry and material properties of the antenna array carrier body, and can significantly improve accuracy of mobile radio direction‐finding systems.

Meta-optimization of bio-inspired algorithms for antenna array design

In this article, a technique called Meta-Optimization is used to enhance the effectiveness of bio-inspired algorithms that solve antenna array synthesis problems. This technique consists on a second optimization layer that finds the best behavioral parameters for a given algorithm, which allows to achieve better results. Bio-inspired computational methods are useful to solve complex multidimensional problems such as the design of antenna arrays. However, their performance depends heavily on the initial parameters. In this paper, the distances between antenna array elements are calculated in order to reduce electromagnetic interference from undesired sources. The results are compared to previous works, showing an improvement on the performance of bio-inspired optimization algorithms such as Particle Swarm Optimization and Differential Evolution. These results are found to be statistically significant based on the Wilcoxon's rank sum test as compared to these methods using the standard parameters proposed in the literature. Furthermore, graphical representations of the Meta-Optimization process called meta-landscapes are presented, showing the behavior of these algorithms for a range of different parameters, providing the best parameter combinations for each antenna problem.

Decision Statistics for Incoherent Signal Detection in Multi-Element Antenna Arrays

We present a detailed study of the characteristics of the exact decision statistic for the optimal incoherent signal detection in a multielement antenna array. The exact decision statistic is derived from a rigorous expression for the likelihood ratio in the case where the useful-signal amplitudes at the antenna-array elements are identical, whereas the phases are random. The analysis is carried out in the space of the variables which are observed at the outputs of the incoherent matched filters performing the initial signal processing at each antenna-array element. Variation in the signal-to-noise ratio is shown to deform the boundary of partitioning of the multidimensional observation space, which results in a variation in the threshold values of the exact decision statistic when the Neyman–Pearson criterion is used. The characteristics of the exact decision statistic and various approximate decision statistics are compared in detail. For the antenna arrays with a large number of elements, the influence of the used decision statistic on the target-missing probability is shown to become rather significant. A new combined decision statistic with the characteristics that are close to those of the exact decision statistic is introduced for a wide signal-to-noise ratio range.