Antenna Array Pattern Research Articles

Ecosystem particle swarm optimization

Particle swarm optimization (PSO) is a well-known swarm intelligence algorithm inspired by the foraging behavior of bird flocking. PSO has been widely used in many optimization and engineering problems due to its simplicity and efficiency, even though there still exist some disadvantages. The standard PSO often suffers with premature convergence or slow convergence when the optimization problem is multimodal or high-dimensional. To overcome these drawbacks, an ecosystem PSO (ESPSO) inspired by the characteristic that a natural ecosystem can excellently keep the biological diversity and make the whole ecosystem be in a dynamic balance is presented in this paper. ESPSO not only prevents the algorithm trapping into local optima but also balances the exploration and exploitation in both unimodal and multimodal problems as compared to other PSO variants. Twenty benchmark functions including unimodal functions and multimodal nonlinear functions are used to test the searching ability of ESPSO. Experimental results show that ESPSO considerably improves the searching accuracy, the algorithm reliability and the searching efficiency in comparison with other six well-known PSO variants and four evolutionary algorithms. Moreover, ESPSO was successfully applied to the antenna array pattern synthesis design and gained satisfactory results.

Feasibility study of installation of solar panels on a high power HF antenna land

In HF broadcasting, the transmitters are typically very powerful. In the case of Turkish Radio and Television (TRT), total transmission average power may reach up to 5 MW. Therefore, it is natural to utilize solar panels as a means of alternative/backup energy for the continuous transmission of RF signal satisfying the requirement of broadcasting. In the TRT HF broadcasting array field, two areas are designated as the candidate areas for solar panel installation. In these areas, electric fields are simulated, measured, and compared. Simulations are done using the Numerical Electromagnetic Code (4nec2). The suitability of the regions for the solar panel installation are evaluated based on the ICNIRP human exposure limits. In addition, 4nec2 simulations are used to see the effect of metal frames of solar panels on the radiation patterns of the short-wave antenna arrays in the two solar panel candidate areas of TRT HF broadcasting station. Simulation results show that metal frames do not seem to have a significant effect on the radiation patterns of the short-wave antenna arrays. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2016.

A Low Phase Noise Fully Monolithic 6 GHz Differential Coupled NMOS LC-VCO

AbstractA fully monolithic 6 GHz low-phase noise Voltage-Controlled-Oscillator (VCO) is presented in this paper. It consists in two LC-NMOS differential VCOs coupled through a resistive network and is implemented on a 0.25 µm BiCMOS SiGe process. This proposed integrated VCO can be used also for phased-array applications to steer the beam over the entire spatial range. In this case, the radiation pattern of the phased antenna array is steered in a particular direction by establishing a constant phase progression in the oscillator chain which can be obtained by detuning the free-running frequencies of the two oscillators in the array. At 2.5 V power supply voltage and a power dissipation of 62.5 mW, the coupled VCO array features a measured worst case phase noise of

Virtual antenna array theory based on high speed mobile communications

For a high speed mobile communication system, Doppler shift affects its performance seriously. In the future, broad band communication based on orthogonal frequency division multiplexing which depends on the orthogonality among sub-carriers will become popular. The absence of the orthogonality due to being destroyed by Doppler shift, leads to the failure of signal demodulation. So Doppler shift must be estimated and compensated for, which is the main purpose of previous work. On the other hand, many applications have shown that Doppler shift can be utilized to acquire the direction and speed or improve the quality of a signal. In this paper, we propose a method of not only estimating and compensating for Doppler shift, but also generating multiple non-frequency shifted signals, which can be regarded as the output of a virtual antenna array. As to the method, uniform phase sampling is the key algorithm. At first, the relation between uniform time sampling and uniform phase sampling is discussed in detail. This relation shows that the equivalence between uniform phase sampling and uniform time sampling is the necessary and sufficient condition for a non Doppler shifted signal. Next, the algorithm of Doppler shift compensation and virtualized antenna array is proposed, in which 1) original Doppler shifted signal is processed with interpolation, 2) new signals are generated by uniform phase sampling and buffered, 3) buffered new signals are read out by uniform time sampling. The theory of this process and the performance improvement for a high speed mobile communications system is mathematically analyzed, and the hardware architecture model of this algorithm is also given. The diversity gain could be obtained when an antenna array is used. In order to verify that this virtualized antenna array has the same benefit, the ability to suppress the interference and the bit error rate is analyzed with numerical simulation. The number of virtual elements and the virtual element distance are two variables related to the direction pattern of virtual antenna array. The effects of these two variables are given by the simulation, showing that the more virtual elements, the narrower beam are obtained. But more virtual elements result in more complicated hardware source. In addition, the communications scenarios of two communications radiators at different sites are simulated to verify whether this algorithm can suppress interference signal. The frequency spectrum of beamformed virtual antenna array signal shows that the interference signal can be suppressed effectively. These characteristics cannot be provided by pure Doppler frequency shift compensation. Thus these results show that high speed mobile communication systems on aircrafts or high speed trains would obtain better performances when a received Doppler shift signal is processed by this method to construct a virtual antenna array.

Certified dual-corrected radiation patterns of phased antenna arrays by offline–online order reduction of finite-element models

This paper presents a fast numerical method for computing certified far-field patterns of phased antenna arrays over broad frequency bands as well as wide ranges of steering and look angles. The proposed scheme combines finite-element analysis, dual-corrected model-order reduction, and empirical interpolation. To assure the reliability of the results, improved a posteriori error bounds for the radiated power and directive gain are derived. Both the reduced-order model and the error-bounds algorithm feature offline–online decomposition. A real-world example is provided to demonstrate the efficiency and accuracy of the suggested approach.

Magnetic antenna excitation of whistler modes. IV. Receiving antennas and reciprocity

Antenna radiation patterns are an important property of antennas. Reciprocity holds in free space and the radiation patterns for exciting and receiving antennas are the same. In anisotropic plasmas, radiation patterns are complicated by the fact that group and phase velocities differ and certain wave properties like helicity depend on the direction of wave propagation with respect to the background magnetic field B0. Interference and wave focusing effects are different than in free space. Reciprocity does not necessarily hold in a magnetized plasma. The present work considers the properties of various magnetic antennas used for receiving whistler modes. It is based on experimental data from exciting low frequency whistler modes in a large uniform laboratory plasma. By superposition of linear waves from different antennas, the radiation patterns of antenna arrays are derived. Plane waves are generated and used to determine receiving radiation patterns of different receiving antennas. Antenna arrays have radiation patterns with narrow lobes, whose angular position can be varied by physical rotation or electronic phase shifting. Reciprocity applies to broadside antenna arrays but not to end fire arrays which can have asymmetric lobes with respect to B0. The effect of a relative motion between an antenna and the plasma has been modeled by the propagation of a short wave packet moving along a linear antenna array. An antenna moving across B0 has a radiation pattern characterized by an oscillatory “whistler wing.” A receiving antenna in motion can detect any plane wave within the group velocity resonance cone. The radiation pattern also depends on loop size relative to the wavelength. Motional effects prevent reciprocity. The concept of the radiation pattern loses its significance for wave packets since the received signal does not only depend on the antenna but also on the properties of the wave packet. The present results are of fundamental interest and of relevance to loop antennas in space.

A PATTERN SYNTHESIS METHOD FOR LARGE PLANAR ANTENNA ARRAY

The pattern synthesis for large antenna arrays is very important because of its wide applications. Several antenna array synthesis techniques for planar antenna array have been developed in the past years. In this paper, a hybrid method for solving antenna array pattern synthesis problem is introduced. The proposed method has three steps. Firstly, the iterative fast Fourier transforms (IFT) is used to generate a number of initial array excitations based on aim pattern. Then, the global optimization method differential evolution strategy (DES) is used to optimize these excitations based on initial excitations. After that, if the optimized pattern does not satisfy the goal, the simulated annealing (SA) method is applied to optimize the excitations until the goal is achieved or the maximum iteration is reached. Several simulation results show that the desired pattern can be effectively synthesized by using the proposed method.

Hysteretic Boundary Conditions for PSO of Antenna Array Pattern Synthesis

Boundary conditions in particle swarm optimizers have been, quite convincingly, shown as an important algorithmic part which restricts the particles within the solution space thereby increasing their scope of participation in solution finding process. As a common practice, velocities of the particles are regulated to bring them back to solution space; however, a different fundamental approach of regulating the position of particles is taken here, particles which go out of solution place are relocated to a position where it was in its past (i.e. hysteretic position) iterative cycle inside the boundary. A six element linear antenna array is taken as the optimization target for the reduction of side lobes in the radiation pattern. Results show better performance of this boundary condition over other established ones in terms of quicker convergence and obtaining better optimization solution.

An Improved Antenna Array Pattern Synthesis Method Using Fast Fourier Transforms

An improved antenna array pattern synthesis method using fast Fourier transform is proposed, which can be effectively applied to the synthesis of large planar arrays with periodic structure. Theoretical and simulative analyses show that the original FFT method has a low convergence rate and the converged solution can hardly fully meet the requirements of the desired pattern. A scaling factor is introduced to the original method. By choosing a proper value for the scaling factor, the convergence rate can be greatly improved and the final solution is able to fully meet the expectations. Simulation results are given to demonstrate the effectiveness of the proposed algorithm.

Pattern Nulling of Linear Antenna Arrays Using Backtracking Search Optimization Algorithm

An evolutionary method based on backtracking search optimization algorithm (BSA) is proposed for linear antenna array pattern synthesis with prescribed nulls at interference directions. Pattern nulling is obtained by controlling only the amplitude, position, and phase of the antenna array elements. BSA is an innovative metaheuristic technique based on an iterative process. Various numerical examples of linear array patterns with the prescribed single, multiple, and wide nulls are given to illustrate the performance and flexibility of BSA. The results obtained by BSA are compared with the results of the following seventeen algorithms: particle swarm optimization (PSO), genetic algorithm (GA), modified touring ant colony algorithm (MTACO), quadratic programming method (QPM), bacterial foraging algorithm (BFA), bees algorithm (BA), clonal selection algorithm (CLONALG), plant growth simulation algorithm (PGSA), tabu search algorithm (TSA), memetic algorithm (MA), nondominated sorting GA-2 (NSGA-2), multiobjective differential evolution (MODE), decomposition with differential evolution (MOEA/D-DE), comprehensive learning PSO (CLPSO), harmony search algorithm (HSA), seeker optimization algorithm (SOA), and mean variance mapping optimization (MVMO). The simulation results show that the linear antenna array synthesis using BSA provides low side-lobe levels and deep null levels.

Analysis of Phased Array Antenna’s Vibration Effects on the Performance of Shipborne MLS

In order to provide precise guidance for the landing of carrier-based aircrafts, the phased array antenna and the principle of time reference scanning beam are used in the shipborne MLS. The phased array antenna is installed under the flight deck of the ship stern, so the vibration could change the relative position of antenna elements, which will cause the navigation error. In this paper, through the establishment of antenna array pattern and phased array antenna vibration error model, an error calibration algorithm is proposed after the simulation of phased array antenna’s random vibration effects on the guiding performance of shipborne MLS in three axes. Computer simulations show that the calibration algorithm could improve the guiding performance of shipborne MLS.

Multi‐beam RF aperture using multiplierless FFT approximation

Multiple independent radio frequency (RF) beams find applications in communications, radio astronomy, radar, and microwave imaging. An $N$-point FFT applied spatially across an array of receiver antennas provides $N$-independent RF beams at $\frac{N}{2}\log_2N$ multiplier complexity. Here, a low-complexity multiplierless approximation for the 8-point FFT is presented for RF beamforming, using only 26 additions. The algorithm provides eight beams that closely resemble the antenna array patterns of the traditional FFT-based beamformer albeit without using multipliers. The proposed FFT-like algorithm is useful for low-power RF multi-beam receivers; being synthesized in 45 nm CMOS technology at 1.1 V supply, and verified on-chip using a Xilinx Virtex-6 Lx240T FPGA device. The CMOS simulation and FPGA implementation indicate bandwidths of 588 MHz and 369 MHz, respectively, for each of the independent receive-mode RF beams.

Formation sparse aperture antenna arrays based on the sequence Costas

To obtain high spatial resolution in sonar, ultrasonic image, radar, seismic, and radio astronomy use active antenna arrays that contain a large number of elements. To reduce the cost of such an antenna arrays used with sparse aperture. In this approach, the antenna array is partitioned into several subarrays. Geometric size subarray equivalent equidistant placement Nc * Nc elements. Subarrays filled Nc elements arranged according to the sequence Costas Nc-th order. Each filled subarrays own Costas sequence. As a result, the number of elements in the array is reduced in times Nc. Form the beam pattern in the main sections close to the plane shape of the beam pattern of equidistant antenna array, and the directivity factor is almost independent of frequency band. The upper frequency is reduced in the directivity factor (π·Nc)/2 times as compared with the plane equidistant antenna array. Using a decaying distribution can be reduced in amplitude level of the side lobe in the principal planes. Thus, by setting the order of the Costas sequence can in each case to optimize the degree of reduction of the number of elements in the array antenna at a predetermined directivity factor.

Robust Efficient Broadband Antenna Array Pattern Synthesis Techniques

This paper presents efficient robust broadband antenna array pattern synthesis techniques with interference cancellation capabilities. The synthesis techniques are able to place multiple broad nulls and isolated point nulls at regions of interest for interference cancellation. The new synthesis algorithms result in improved performance broadband antenna array processors. The presented synthesis techniques are computationally more efficient than the existing synthesis techniques. The paper includes numerical simulations that demonstrate the performance of the new techniques compared to existing methods.

Pattern optimisation algorithm for vertical cell splitting system with active antenna arrays

A genetic algorithm (GA)-based pattern optimisation of active array antenna (AA) vertical cell splitting system is proposed. In the proposed algorithm, a joint optimisation method of inner cell pattern and outer cell pattern is designed, and GA is applied to optimise the array's amplitude excitations for reducing the interference in AA vertical cell splitting system. The simulation results and performance analysis demonstrate the feasibility and validity of the proposed algorithm. In comparison to the conventional identical-excitation active AA patterns, the optimised results show that significant gain in both cell average throughput and cell edge throughput is obtained.

Efficient synthesis of 4D antenna arrays using a bitwise evolutionary genetic algorithm

In this paper, a bitwise evolutionary genetic algorithm GA is proposed to synthesize the power patterns of 4D antenna arrays efficiently. Within the binary optimized time sequences of 4D antenna arrays, the genes of 1 and 0 represent switch-on and switch-off period of antennas, respectively. Gene retention probability, which relates to the fitness values of each individual in the whole group, is proposed to evaluate how good each gene is. With the proposed gene retention probability, the crossover operator in traditional GA is replaced with a new method to generate the next generation. The proposed algorithm is applied to the synthesis of 4D antenna arrays with binary optimized time sequences, and the performance of the proposed algorithm is compared with that of traditional GA on the condition of the same parameter settings. The comparison results show that bitwise evolutionary GA improves the optimization efficiency significantly, which reduces the computation time as much as 85% on average of the traditional GA with the same goal. Copyright © 2014 John Wiley & Sons, Ltd.

향상된 적응형 유전 알고리즘을 이용한 컨포멀 배열 안테나의 빔 합성 연구

본 논문에서는 2차 함수 곡선의 회전체 곡면 위에 있는 배열 안테나의 빔 합성을 위한 Enhanced Adaptive Genetic Algorithm(EAGA)을 제안하였다. 제안된 알고리즘은 더 빠른 수렴 속도와 더 낮은 비용함수 값을 얻기 위해 Adaptive Genetic Algorithm(AGA)과 Invasive Weed Optimization(IWO)을 결합시켰다. 각 안테나 소자의 급전 크기와 위상의 최적화된 값은 EAGA를 통해 구하였으며, 이 결과를 통해 EAGA가 컨포멀 배열 안테나의 패턴 합성 알고리즘으로써 AGA보다 더 우수함을 보였다. This paper proposes an enhanced adaptive genetic algorithm(EAGA) dedicated to pattern synthesis of array antenna which conforms to a curved surface of rotation with quadratic function. EAGA combines adaptive genetic algorithm(AGA) with invasive weed optimization(IWO) for the faster convergence and the lower cost value of the cost function. The amplitude and phase of each excited weighting factor are optimized to meet the required goals using EAGA. The EAGA results indicate that the proposed algorithm is superior to AGA when applied to the problem of conformal array antenna pattern synthesis.

A quantized water cycle optimization algorithm for antenna array synthesis by using digital phase shifters

In this article, a quantized water cycle algorithm (QWCA) is used for the antenna array pattern synthesis with low side-lobe levels (SLLs) and nulls at desired directions by using four-bit digital phase shifters. In addition to the standard features as a metaheuristic algorithm, QWCA has an internal quantization mechanism and a precalculated array factor method. The latter provides an accelerated procedure to QWCA under favour of the digitized values that can be stored in a three-dimensional array. This acceleration is based on the reality that the accessing data in the memory need less time than the usage of the mathematical functions throughout the optimization process. The internal quantization mechanism of QWCA is utilized to achieve digital values matching to the discrete values of the phase shifter instead of the simple rounding up/down routines after optimization. The numerical results showed that QWCA can obtain very good SLLs and null depth levels (NDLs) on the synthesized pattern. Moreover, the results are achieved in remarkably short optimization times. SLL and NDL values obtained by QWCA are also compared with the available literature values. The comparisons reveal that QWCA is able to produce better results than the other compared alternatives. © 2014 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:21–29, 2015.

Conformal antenna arrays with E3M3 radiators

Design relationships for computer simulation of radiation patterns of conformal antenna arrays are derived. Results of the comparative analysis of radiation patterns of arrays with spherical, hemispherical, and disk-shaped apertures in which the radiators consist of three electric dipoles and three magnetic dipoles (E3M3) are presented. It is shown that application of E3M3 radiators with proper orientation of their axes in conformal antenna arrays can increase the directive gain in the main lobe.

MUTUAL COUPLING EFFECT ON MIMO ANTENNA

To reduce mutual coupling effect on MIMO Antenna this paper presents the analysis of bent ground plane antennas for multiple-input-multiple-output (MIMO). First, the three plate antenna array patterns of the envelope correlation coefficients are proposed to evaluate the diversity performance of antennas in MIMO systems. Following this, a compact three-element suspended plate antenna array with a bent ground plane is presented. The diversity performance of the design is experimentally and numerically analysed.