Adaptive Antenna-Activation Based Beamforming for Large-Scale MIMO Communication Systems of High Speed Railway

Large-scale array aided beamforming improves the spectral efficiency(SE) as a benefit of high angular resolution.When dual-beam downlink beamforming is applied to the train moving towards cell edge,the inter-beam ambiguity(IBA) increases as the directional difference between beams becomes smaller.An adaptive antenna activation based beamforming scheme was proposed to mitigate IBA.In the district near the base station(BS),all antenna elements(AEs) were activated to generate two beams.As the distance from the train to the BS increased,only the minimum number of AEs satisfying the resolution criterion would be activated.At the cell edge,one beam was switched off due to intolerable IBA.The proposed scheme can achieve SE gain to the non-adaptive scheme and show more robustness against the direction-of-arrival(DOA) estimation error.

Antenna selection based on large-scale fading for distributed MIMO systems

An antenna selection algorithm based on large-scale fading between the transmitter and receiver is proposed for the uplink receive antenna selection in distributed multiple-input multiple-output(D-MIMO) systems. By utilizing the radio access units(RAU) selection based on large-scale fading,the proposed algorithm decreases enormously the computational complexity. Based on the characteristics of distributed systems,an improved particle swarm optimization(PSO) has been proposed for the antenna selection after the RAU selection. In order to apply the improved PSO algorithm better in antenna selection,a general form of channel capacity was transformed into a binary expression by analyzing the formula of channel capacity. The proposed algorithm can make full use of the advantages of D-MIMO systems,and achieve near-optimal performance in terms of channel capacity with low computational complexity.

Review of dynamics and active control of large-scale space membrane antenna

Large-scale space membrane antennas have significant potential in satellite communication,space-based early warning,and Earth observation.Because of their large size and high flexibility,the dynamic analysis and control of membrane antenna are challenging.To maintain the working performance of the antenna,the pointing and surface accuracies must be strictly maintained.Therefore,the accurate dynamic modeling and effective active control of large-scale space membrane antennas have great theoretical significance and practical value,and have attracted considerable interest in recent years.This paper reviews the dynamics and active control of large-scale space membrane antennas.First,the development and status of large-scale space membrane antennas are summarized.Subsequently,the key problems in the dynamics and active control of large membrane antennas,including the dynamics of wrinkled membranes,large-amplitude nonlinear vibration,nonlinear model reduction,rigid-flexible-thermal coupling dynamic modeling,on-orbit modal parameter identification,active vibration control,and wave-based vibration control,are discussed in detail.Finally,the research outlook and future trends are presented.

Hybrid Precoding for mm Wave Massive MIMO Systems with Different Antenna Arrays

In this paper, the performance of hybrid precoding is investigated for mmWave massive MIMO systems with different antenna arrays. The hybrid precoding with partially connected architecture (PCA) is adopted. The spectral efficiency (SE) and received energy efficiency (EE) are investigated by considering four types of antenna arrays, including uniform linear array (ULA), uniform rectangular planar array (URPA), uniform hexagonal planar array (UHPA), and uniform circular planar array (UCPA), respectively. We focus on analysis at the antenna response vector and utilize the idea of orthogonal matching pursuit algorithm to seek the optimal hybrid precoder. Furthermore, the trade-off of precoding architectures is studied between SE and received EE. Simulation results show that if the uniform planar array antenna is more concentrated, the SE and receive EE will be higher. Considering SE and received EE, the performance of planar arrays outperform linear array. There exist different optimal radio-frequency chain numbers to maximize the SE for planar array and linear array. In addition, the PCA can achieve relatively higher received EE while the SE is close to the fully connected architecture and the full digital architecture.

Decoupling technique of patch antenna arrays with shared substrate by suppressing near-field magnetic coupling using magnetic metamaterials

In this paper,we propose the decoupling technique of patch antenna array by suppressing near-field magnetic coupling（NFMC） using magnetic metamaterials.To this end,a highly-integrated magnetic metamaterials,the substrate-integrated split-ring resonator（SI-SRR）,is firstly proposed to achieve negative permeability at the antenna operating frequency.By integrating SI-SRR in between two closely spaced antennas,magnetic fields are blocked in the shared substrate due to negative permeability of SI-SRR,reducing NFMC between the two antennas.To verify the technique,a prototype was fabricated and measured.The measured results demonstrated that the isolation can be enhanced by more than 17 dB even when the gap between the two patch antennas is only about 0.067 A.Due to high integration,this technique provides an effective alternative to high-isolation antenna array.

A Review of the Four Dimension Antenna Arrays

The four dimensional （4D） antenna arrays introduce a fourth dimension, time, into conventional antenna arrays to offer greater flexibility in the design of high performance antenna arrays. This paper presents the tutorial on the study of 4D antenna arrays and the review of the recent research findings on 4D antenna arrays. Issues considered include the theory of 4D antenna arrays, different time modulation schemes, numerical simulation results, and some experimental results on their applications to low sidelobe designs. Throughout the discussion, some challenging issues on the study of 4D antenna arrays arc highlighted.

Design and Analysis of Microstrip Antenna Arrays in Composite Laminated Substrates

In high performance aerospace systems where weight and aerodynamics are of major concern, fiber reinforced composite laminates can be tailored to achieve desirable mechanical properties and accommodate low-profile microstrip antenna. This work aims at the analysis of microstrip antenna array embedded in composite laminated substrates. The size of a single antenna is first calculated by spectral domain analysis to model the effects of the substrate’s electromagnetic property and the orientation of the laminate layers. The antenna array as well as the feed network, composed of microstrip transmission lines, quarter wave-length impedance transformers, and T-junction power dividers, is then tuned to accommodate the effects of the coupling between the antenna elements and the feed network loss. The performance of the 1 × 2, 1 × 4, and 1 × 8 linear array and 2 × 2 and 2 × 4 planar array are shown to have better directivity when embedded in composite laminated substrate compared with those when attached on isotropic substrate. Both 1 × 2 and 1 × 4 arrays at 2.4 GHz are validated experimentally to achieve better coverage.

A Novel Beam Design Method for mm Wave Multi-Antenna Arrays with Mutual Coupling Reduction

To overcome the mutual coupling (MC) of multiple antennas in millimeter wave (mmWave) communication systems, a novel beam design method with low complexity is proposed in this paper. Firstly, an equivalent channel model incorporating the effect of MC is analyzed and established, and then an optimal precoding / combiner vector for beamforming is derived. On this basis, by using greedy geometric (GG) algorithm, a novel hybrid beam design method is proposed. Finally, the performance of proposed method is analyzed and compared with other traditional ones. The simulation results show that the proposed method has better suppression of the MC effect as well as lower complexity.

A COMBINED FULL-WAVE BCG-FFT METHOD FOR RADIATION OF MICROSTRIP ANTENNA ARRAYS

A method of combining BiConjugate Gradient(BCG) with Fast Fourier Transform(FFT) to analyze the radiation of microstrip antenna arrays is presented, where the spatially discrete BCG-FFT for analyzing microstrip structure is used and the del operators on Green's functions are transferred from the singular kernel to the expansion and testing functions. The resultant equations are solved by using BCG method in which the matrix-vector product is evaluated efficiently with FFT. The calculated patterns are in good agreement with the measured data.

Equivalent Joint Space-Time Multiuser Detection for Uplink ISI-Corrupted Multicarrier CDMA Systems with Arbitrary Antenna Arrays

The multicarrier code division multiple access (MC-CDMA) systems without cyclic prefix (CP) hold a fine spectral efficiency though they are unavoidably corrupted by the intersymbol interference (ISI) over the finite impulse response (FIR) channel. We call MC-CDMA systems without CP the ISI-corrupted MC-CDMA systems in some sense. Considering the fact that combining antenna arrays with so-called ISI-corrupted MC-CDMA systems is advantageous in suppressing cochannel interference in cellular communication systems, this paper investigates ISI-corrupted MC-CDMA systems with base station antenna arrays. Joint space-time multiuser detection (MUD) schemes for DS-CDMA systems with antenna arrays have drawn much attention recently. Based upon them, we can derive the equivalent joint spatial-temporal MUD scheme for ISI-corrupted MC-CDMA systems with antenna arrays. In order to achieve this goal, an equivalent space-time estimation method of uplink vector channel is first derived for the ISI-corrupted MC-CDMA system with the arbitrary antenna array over frequency-selective fading channels. Then, based on the estimated equivalent space-time channel, an equivalent joint space-time multiuser detector is constructed. Computer simulations illustrate that our algorithm is more robust against noise and can well mitigate multiple access interference (MAI) in multiuser scenarios.

An Optimized Design of Antenna Arrays for the Smart Antenna Systems

In recent years,there has been an increasing demand to improve cellular communication services in several aspects.The aspect that received the most attention is improving the quality of coverage through using smart antennas which consist of array antennas.this paper investigates the main characteristics and design of the three types of array antennas of the base station for better coverage through simulation(MATLAB)which provides field and strength patterns measured in polar and rectangular coordinates for a variety of conditions including broadsides,ordinary End-fire,and increasing directivity End-fire which is typically used in smart antennas.The method of analysis was applied to twenty experiments of process design to each antenna type separately,so sixty results were obtained from the radiation pattern indicating the parameters for each radiation pattern.Moreover,nineteen design experiments were described in this section.It is hoped that the results obtained from this study will help engineers solve coverage problems as well as improve the quality of cellular communication networks.

Nonequidistant two-dimensional antenna arrays based on magic squares

New methods of synthetizing nonequidistant sparse antenna arrays based on the properties of magic squares are studied.The methods of construction and algorithms of synthesis of two-dimensional antennas based on them providing a high degreeof dilution and sufficiently small side radiation are proposed.The methods for construction of such antennas and their maincharacteristics are considered.

Correction Factor for Power Gain in Antenna Arrays

Antenna array gain is a relative measure of performance defined differently in various literature. Most definitions of gain are not power consistent, and thus cannot be used directly in link budget analysis. In this short paper, we present a power correction factor for common definitions of power gain of antenna arrays that allows them to be used in standard link budget calculations.

Formulation of Optimization Problems with Radiation Field Phases as Design Variables for Pattern Synthesis of Linear Antenna Arrays

Pattern synthesise of antenna arrays is usually complicated optimization problems,while evolutionary algorithms(EAs)are promising in solving these problems.This paper does not propose a new EA,but does construct a new form of optimization problems.The new optimization formulation has two differences from the common ones.One is the objective function is the field error between the desired and the designed,not the usual amplitude error between the desired and the designed.This difference is beneficial to decrease complexity in some sense.The second difference is that the design variables are changed as phases of desired radiation field within shaped-region,instead of excitation parameters.This difference leads to the reduction of the number of design variables.A series of synthesis experiments including equally and unequally spaced linear arrays with different pattern shape requirements are applied,and the effectiveness and advantages of the proposed new optimization problems are validated.The results show that the proposing a new optimization formulation with less complexity is as significant as proposing a new algorithm.

Optimal Design of Wireless Power Transmission Systems Using Antenna Arrays

Three design methods for wireless power transmission(WPT)systems using antenna arrays have been investigated.The three methods,corresponding to three common application scenarios of WPT systems,are based on the method of maximum power transmission efficiency(MMPTE)between two antenna arrays.They are unconstrained MMPTE,weighted MMPTE,and constrained MMPTE.To demonstrate the optimal design process with the three methods,a WPT system operating at 2.45 GHz is designed,simulated,and fabricated,in which the transmitting(Tx)array,consisting of 36 microstrip patch elements,is configured as a square and the receiving(Rx)array,consisting of 5 patch elements,is configured as an L shape.The power transmission efficiency(PTE)is then maximized for the three application scenarios,which yields the maximum possible PTEs and the optimized distributions of excitations for both Tx and Rx arrays.The feeding networks are then built based on the optimized distributions of excitations.Simulations and experiments reveal that the unconstrained MMPTE,which corresponds to the application scenario where no radiation pattern shaping is involved,yields the highest PTE.The next highest PTE belongs to the weighted MMPTE,where the power levels at all the receiving elements are imposed to be equal.The constrained MMPTE has the lowest PTE,corresponding to the scenario in which the radiated power pattern is assumed to be flat along with the Rx array.

Comparison of Circular Sector and Rectangular Patch Antenna Arrays in C-Band

The circular sector patch antenna is studied in C-band (4 GHz - 8 GHz). In this paper, we present steps of designing the circular sector antenna then a comparison with a rectangular antenna in literature. High Frequency Structure Simulator (HFSS) software is used to compute the gain, axial ratio, radiation pattern, and return loss S11 of proposed antenna. Based on the designed patch antenna, many phased arrays will be simulated using HFSS. The impact of distance between element, number of element and phase will be checked. Obtained results are analyzed and compared with literature.

Analysis of Large Slotted-Waveguide Antenna Arrays Using the Parallel DDA-FE-BI-MLFMA

An efficient analyzing approach is presented for large slotted-waveguide antenna arrays by using hybrid finite element-boundary integral-multilevel fast multipole algorithm（FE-BI-MLFMA）in this paper.A simple computation model for slotted-waveguide antenna is presented by using thin current probe excitation and perfectly matched layer（PML）absorber.Since each slotted-waveguide antenna can be considered as a single sub-domain,the domain decomposition algorithm（DDA）can be applied to FE-BI-MLFMA to greatly reduce the computation resources and achieve high efficiency.This DDA-FE-BI-MLMFA is parallelized to further strength its capability.The comparisons of the computed radiation patterns with measured data and results from the commercial software show that our method has good accuracy for slottedwaveguide array.Then the influence of mutual coupling between adjacent slotted-waveguides is studied.To demonstrate capability of the presented method,a carefully designed large X-band slotted-waveguide antenna array containing eighteen waveguides with Taylor amplitude and inverse phase excitation distribution are analyzed in the paper.

Substrate Integrated Waveguide Based Monopulse Slot Antenna Arrays for 60 GHz Applications

Monopulse slot antenna arrays based on substrate integrated waveguide （SIW） are proposed for the application of 60 GHz mono- pulse tracking systems in this paper. The sum-difference monopulse comparator can provide a high amplitude and phase balance over wide frequency band and no phase delay technique is required for the difference channel. Resonant slot antennas are adopted as the radiating elements since they can be integrated with the sum-difference monopulse comparator in a single layer with a compact size. Two monopulse arrays with 2× 4 and 4×4 slot elements are designed, fabricated, and measured. Measured results show that the proposed antenna arrays have wide bandwidth covering the unlicensed 60-GHz band. The peak sum beam gain is 13.85 dBi for the 2 ×4 element array and 16.24 dBi for the 4×4 element array. The peak difference beam gain is 11.20 dBi for the 2×4 element array and 12.11 dBi for the 4×4 element array and the maximum null depth can reach -40 dB.

Speed-Sensitive Weighting Algorithm for Digital Beamforming of Adaptive Antenna Arrays

One of the main objectives of adaptive antenna array processing is reducing the computational complexity and convergence time in a joint state. This article proposes a speed-sensitive adaptive algorithm for estimating the weights of smart antenna systems based on least mean squares (LMS) or constant modulus (CM) algorithms. According to the next estimated location as well as the source velocity, this novel proposed weighting algorithm selects those weights that have a higher effect on the radiation pattern and will then form the antenna pattern by only changing these weights. In this research, 3 versions of the new algorithm named as: Not-zero (Leaves half number of weights as it is the other half), Zero (Sets half number of weights to be zero and estimates other half), and Updating (Leaves half of weights unchanged and estimates other half in one phase and updates all weights in the next phase) are proposed. Through simulation of these 3 versions of speed-sensitive algorithms and comparing among conventional full weight LMS and CM algorithms, new LMS-based and CM-based algorithms have been finally proposed that offer reduced complexity and acceptable performance at different signal to noise ratios (SNRs). In this investigation, three channel scenarios are simulated which are as follows: pure noisy channel, channel with one interferer and channel with two interferers. In accordance with the simulation results, an appropriate algorithm based on weighting half number of array elements and updating all existing weights between two consecutive times to avoid error propagation effect has been proposed.

Achieving Directionality and Transmit Diversity via Integrating Beam Pattern Scanning (BPS) Antenna Arrays and OFDM

In this paper, we introduce a novel merger of antenna arrays with scanning beam patterns, and Orthogonal Frequency Division Multiplexing (OFDM) systems. Controlled time varying phase shifts are applied to the antenna array elements mounted at the base station with beam patterns directed toward the desired user. This creates a small beam pattern movement called Beam Pattern Scanning (BPS). In rich scattering environments BPS creates a time varying environment leading to time diversity exploitable at the receiver enhances its probability-of-error performance. Here, we apply OFDM signals to BPS antenna arrays, and we achieve: (1) directionality, which supports Space Division Multiple Access (SDMA);and (2) a time diversity gain, which leads to high performance. We discuss the structure of the base station antenna array and the OFDM receiver that exploits time diversity. We also introduce the merger of BPS and multi-carrier OFDM (MC-OFDM) systems. In MC-OFDM each bit is transmitted over all sub-carriers after serial to parallel conversion. BPS/ MC-OFDM receiver exploits both time diversity inherent in BPS, and frequency diversity inherent in MC-OFDM transmission technique. Simulation results show high Probability-of-error performance is achie- vable via BPS/OFDM and BPS/MC-OFDM schemes comparing to the traditional OFDM and MC-OFDM, respectively. Simulations also reveal that MC-OFDM system as well as its merger with BPS is capable of mitigating large Peak-to-Average Ratio (PAPR) problem in traditional OFDM system. In addition, performance simulations with coded OFDM (COFDM) and coded MC-OFDM (MC-COFDM) and their merger with BPS are studied.