Traditional beamforming algorithms are only applicable to ideal environments. When the array antenna receives data under circumstances of small snapshots or large signal-to-noise ratio(SNR), noise eigenvalues of classic sample matrix inversion(SMI) and other algorithms will diverge, resulting in beam performance reduction. Therefore, a diagonal loading beamforming algorithm based on aquila optimizer is proposed in this paper. First, the identity matrix and the original covariance matrix are linearly combined, then aquila optimizer is used to optimize the process of the matrix diagonal loading, finally, the obtained improved loading value is combined with SMI to form the beam. Simulation results show that the proposed algorithm can improve the beam distortion caused by divergence of small eigenvalues, and performs well in high SNR, low SNR or small snapshots. Meanwhile, it has better stability and adaptability compared with SMI and traditional diagonal loading algorithm.

In view of the decline in the positioning accuracy of the vehicles with small snapshots, this paper proposes a direction of arrival(DOA) estimation method based on deep unfolded network to assist the global positioning system to achieve high-precision locating. Firstly, the signal emitted from the on board unit installed on the vehicle is received by the array antenna of the road side unit(RSU), then RSU transmits the array data to cloud service platform, in which the traditional fixed point continuation algorithm is improved by using l1 norm instead of l2 norm, and the adaptive outlier point tracking algorithm is used to deal with the problem of symbol flipping caused by noise. Then we unfold the improved fixed point continuous algorithm for obtaining a neural network. In order to improve the DOA estimation performance and convergence speed, this paper uses the black widow optimization algorithm to determine the soft threshold shrinkage parameters. According to the mapping between the signal and the array manifold matrix, the DOA of the target is estimated, and its location can be evaluated from the geometry relation between vehicle and RSU. The simulation results show that the algorithm proposed in this paper has better direction finding performance and improves the vehicle positioning accuracy under small snapshots and high signal-to-noise ratio effectively.

In this paper, the antenna reconfigurable technology is used to redesign a whip antenna in different sub-bands of high frequency (HF). According to the electrical characteristics of the antenna, on the one hand, two different radiation whip heights are designed to solve the problem of pattern up-warping in the high-frequency band; on the other hand, a common upper loading network and several different adjusting inductors and matching networks are designed for each sub-band to achieve high gain and efficiency when keeping good voltage standing wave ratio (VSWR) characteristics. Five sub-bands of the 10-m HF whip antenna are reconfigured through the actual selection of radiation height, adjusting inductance, and matching network by radio frequency (RF) switch. The antenna load and matching network are optimized by grasshopper optimization algorithm (GOA), and integrated into the antenna body by using the printed circuit technology. The scaled prototype of 1 m frequency reconfigurable antenna is manufactured and tested, which shows that the VSWR is all -2.5 dB with an average value of 3.90 dB; the efficiency is all >18.2% with an average value of 71.59%, and the patterns all keep horizontal omnidirectional without the phenomenon of up-warping.

In this study, a new type of horizontal radiation blade structure is proposed and applied to the very high frequency (VHF) broadband whip antenna. The influence of the radius, length, number of branches of horizontal radiation blade and its distribution on the whip body on the electrical performance of the whip antenna is analysed separately to design a more suitable structure, and then an algorithm optimization of single loading and broadband matching network is carried out for further impedance matching. The simulation and measured results both show that compared with the existing broadband whip antenna, the gain and efficiency of the proposed antenna are significantly improved while maintaining a good voltage standing wave ratio (VSWR) over the frequency band of 30–300 MHz, all the VSWR are <3 with an average value of 2.0; all the maximum gain are >−3.5 dB, with an average value of 2.2 dB; and all the efficiency are >15%, with an average value of 47.7%; the pattern deviation in higher frequency is also suppressed to some extent. The proposed antenna has small size, wider bandwidth and higher radiation performance, which is suitable for vehicle-borne and ship-borne VHF communication.

Antenna arrays with high directivity, low side-lobe level, and null control in desired direction and whip antenna with wider bandwidth both need to be optimized to meet different needs of communication systems. A new natural heuristic algorithm simulating social behavior of grasshoppers, grasshopper optimization algorithm (GOA), is applied to electromagnetic field as a new effective technology to solve the antenna optimization problem for the first time. Its algorithm is simple and has no gradient mechanism, can effectively avoid falling into local optimum, and is suitable for single-objective and multiobjective optimization problems. GOA is used to optimize the side lobe suppression, null depth, and notch control of arbitrary linear array and then used to optimize the loading and matching network of 10-meter HF broadband whip antenna compared with other algorithms. The results show that GOA has more advantages in side-lobe suppression, null depth, and notch control of linear array than other algorithms and has better broadband optimization performance for HF whip antenna. The pattern synthesis and antenna broadband optimization based on GOA provide a new and effective method for antenna performance optimization.

A novel chaotic adaptive butterfly mating optimization (CABMO) is proposed to be used in synthesizing the beam pattern. In order to improve the optimization accuracy and avoid trapping in the local optimum, the homogeneous chaotic system and adaptive movement mechanism are combined into the proposed algorithm, where the initialization and redistribution of butterflies are chaotically dispersed with an adaptive movement closely related to the ultraviolet changes. After validating the performance of CABMO through several benchmark functions with different dimensions, the improved algorithm outperforms when compared to other state-of-the-art nature-inspired metaheuristic algorithms. The proposed algorithm is then used to understand any linear array problems in terms of the sidelobe reduction. Finally, a CABMO strategy is utilized to optimize the mutual coupling model of the closely spaced VLF umbrella arrays. Results show that the optimized structure has comfortably outperformed the original structure. Full scanning of wave positions is realized from 15 to 30kHz. The synthesis patterns are close to the theoretical optimum. The optimized results of the radiation performance and synthesized patterns demonstrate that the pattern synthesis and antenna structure optimization based on the CABMO algorithm provides a novel idea for antenna array optimization.

Aiming at the problems of low gain, low efficiency in low frequency band and warping pattern in high frequency band of the existing HF broadband whip antenna, this paper introduces frequency reconfigurable antenna technology and radiation blades loading technology to redesign whip structure, loading and matching network in different bands, and designs a kind of frequency-reconfigurable whip antenna with improved gain and efficiency. The whip body structure, loading and matching network structure of the antenna in each band are optimized, and the on-off control is carried out through the radio frequency switch according to the actual needs. The results show that the standing wave ratio of the proposed antenna is all less than 3, the average value is 2.32; the gain is all greater than -2dB, the average value is 3.63dB; the total efficiency is all over 20%, the average value is 72.77%, and the pattern keeps horizontal omnidirectional in the whole short wave band without upward warping phenomenon.

In this study, the radiation characteristics of the control source of extremely low frequency (CSELF) horizontal line-current antennas are studied by the reciprocity theorem. The radiation field strength expressions of the CSELF L-type horizontal line-current antenna are derived on the basis of a field-direction coefficient in the spherical earth-ionosphere cavity. The estimation results of the super low frequency/extremely low frequency (SLF/ELF) wave are provided with regard to the conductivity, the propagation distances and the water-depth. The propagation characteristics of the CSELF wave are calculated under different conditions and are compared to Bannister's method. The effectiveness of the proposed method is validated by a case study.

Aiming at the problems of low gain, low efficiency at lower frequency, and warping in pattern at higher frequency of 10-meter high frequency (HF) whip antenna, the whip antenna is loaded and matched with the network in different bands using Grasshopper Optimization Algorithms (GOA) and antenna reconfiguration technology, so a new frequency reconfigurable broadband whip antenna is designed in this paper. According to the electrical characteristics of the 10-meter HF whip antenna, this paper divides short wave frequency into three bands and designs its radiation structure, loading, and matching network for each band of antenna, respectively. GOA is introduced into the research and design of antenna to optimize component parameters of the loading network and matching network. The results show that the antenna in lower frequency band can be improved at most, the maximum gain growth up to 5.8dB (from -10.3 dB to -4.5 dB), and the maximum efficiency growth up to 8.5% (from 3% to 11.5%); the gain and efficiency in high frequency band are greatly improved too, and the phenomenon of warping in the pattern is effectively avoided.

Non-Foster matching circuits are those that can function as negative capacitors or inductors, and can thus overcome the gain-bandwidth limitation of passive matching circuits for antennas. This paper presents a non-Foster matching circuit (NFC) for a very low frequency (VLF) receiver loop antenna. The bandwidth of the antenna was improved by 383%, and the average gain was improved in most bands compared to a passive matching circuit (over 15-30 kHz). In contrast to circuits reported in other publications, the signal to noise ratio (SNR) of the passive matching network performed better than the non-Foster matching network. To analyze this phenomenon, a noise model was developed for the simplified balanced NFC, and noise analysis was conducted between the non-Foster and passive matching networks, which indicates that the non-Foster matching circuits cannot provide a better SNR performance than the passive matching circuits under low noise figure level receiver conditions.

The output power of antennas is an important factor affecting the radiation performance of umbrella antenna arrays. Considering the power limit of very-low-frequency (VLF) umbrella arrays and the uncontrollable directivity, we propose a novel method for the spatial power-combining (SPC) of VLF umbrella arrays. Using multiple groups of feeders, the problem of phase shifting of the signals can be solved for VLF arrays. In the high frequency portion of the VLF range (25–30 kHz), this novel method can improve the efficiency of VLF arrays by 26% in the special directivity. A model of a trideco-tower umbrella antenna array is established in the FEKO simulation software. The simulation results show that compared with the in-phase feeding, the VLF transmitting antenna array forms the main beam in all directions. The array gain of the umbrella phased array in the 0◦ (180◦) beam position is larger than 1.1 dB. The front-to-back ratio of the arrays is 3.7 dB. Compared with the in-phase feed mode, the directivity of the phased array enhances and the efficiency increases markedly. The simulation results demonstrate the effectiveness of the proposed method.

In the detector design of RFID, radio frequency identification devices, the antenna beam needs to meet the conditions of high gain and adjustable direction to cover the room and corridor in indoor environment,. In this paper, an 3-element arc array of microstrip antenna based on circularly polarized microstrip patch antenna are studied by quasi-Newton method in HFSS(high-frequency structure simulator). In this array, three probe-fed circularly polarized microstrip patch antenna, whose working frequency is 915Mhz, is placed on an arc array and the two array elements on both sides are symmetric. It is investigated that gain and bandwidth of the antenna array can be enhanced and the beam direction can be adjusted by properly arranging these array elements. The driven patch is a perturbed square one with two diagonal corners truncated in order to realize circular polarization. The model of antenna array has a gain of 5.9dB with a 3dB axial ratio bandwidth of 23.8%. The proposed antennas have been made and measured. The experimental results are basically the same as the simulation results. The research results provide a new idea for the design of microstrip antenna array, which can obtain higher gain while adjusting the beam direction of the antenna array.

A combined analysis method for determining the structural and electrical performance of very-low-frequency (VLF) T-type transmitting antennas with a complex structure is proposed. By using the finite element method for analyzing the antenna’s structural performance and the moment method for determining the antenna’s electrical performance, the structural entity model of the antenna is transformed into an electrical model by extracting the position and displacement information of the antenna curtain, thereby determining the electrical performance index of the transmitting antenna. An actual VLF T-type transmitting antenna is analyzed using this method. A comparison between the calculated results and measured data shows that this method is effective and feasible. In addition, by optimizing the sag of the antenna’s curtain, it is demonstrated that the radiation efficiency of the transmitting antenna can be further improved using this method, and the radiation patterns of the initial state and optimized antenna stay almost the same. This method provides guidance for the synthesis design of other VLF transmitting antennas with complex structures.

This paper has explained the defects in the traditional passive adaptive cancellation technology under the tight coupling interference, introduced an active adaptive cancellation technology (AACT), and offered a mathematical model of the active adaptive cancellation system, as well as the formulae of interference cancellation ratio (ICR) and convergence time for simulation and experiment. The results show that the system is characterized by high ICR and short convergence time and that the AACT can effectively deal with the tight coupling interference and its application can expand further.

This paper has introduced the active broadband matching technology, including designing a non-Forster circuit and a broadband matching circuit, to effectively solve the problems of low gain and efficiency covering the low band(3~8MHz) for the certain 10 meter high frequency(HF) broadband whip antenna. Combined with ADS and FEKO software simulation, the voltage standing-wave ratio(VSWR) covering the low band is less than 2.3, the gain is more than 0dB, the efficiency is greater than 32%, which significantly improves the electrical characteristics of the whip antenna covering the low band, and provides an effective method for this HF antenna to realize frequency-reconfigurable design.

A cooperative analysis method of antenna structures and electrical performance based on the finite element method and the moment method is proposed to study the influence of structure deformation on the electrical performance of the very low frequency (VLF) transmitting antennas under different working conditions.Firstly,the antenna curtain is optimized by the zero order optimization algorithm under the condition that the safety factor of the antenna meets the requirements,and an antenna curtain structure form with theoretical better electrical performance is generated.Then,the antenna node information is extracted,and a new method of file format conversion is used to transform the optimized antenna curtain's structure model to an electrical model for moment analysis.Finally,the electric model is processed to analyze the effects of different ice coverages and wind speeds on the electrical performance of the antenna.The method is used to analyze the electrical performance of a VLF T-type transmitting antenna under different working conditions.It is found that the radiation resistance and loss resistance of the antenna change under different working conditions,and the radiation efficiency of the antenna has different degrees of reduction under ice and winding state.The proposed method has a certain guiding significance for the cooperative analysis of the structure and electrical performance for other types of complex structured wire mesh antennas.

In the above-named work [ibid., vol. 64, no. 5, pp. 1681–1688, May 2016] in the line one below (4), Pn is undefined and should be distinguished from Pn in line four of page 1682. In the sentence one below (4), some statements are incorrect and redundant. The corrected expression of that sentence are provided.

In [1, p. 1683], in the line one below (4), $P_{n} $ is undefined and should be distinguished from $P_{n} $ in line four at p. 1682. In the sentence one below (4), some statements are incorrect and redundant. The corrected expression of that sentence should be “we can have the maximum possible radiation pattern when $p_{m} =-Kcdot dcdot cos (theta _{0} )$ and $p_{n} =-Kcdot sin (theta _{0} )(acdot cos (phi _{n} )cdot cos (phi _{0} )+bcdot sin (phi _{n} )cdot sin (phi _{0} ))$ .” And in line 7 after (4), $vartheta $ is undefined and $vartheta $ should be correct to $theta $ . Equation (5) is incorrect. The correct equation follows: begin{equation*} F_{mathrm{ Hyper}} = big {{ ( { | {F_{mathrm{ Left}}} |+ | {F_{mathrm{ Right}}} |} )^{k}- ( { | {F_{mathrm{ Left}} -F_{mathrm{ Right}}} |} )^{k}} big }^{frac {1}{k}}.tag{5}end{equation*}

A new research method for intelligent community based on multi-living agent was presented. The intelligent community system architecture and the application specific intellectual endowment were analyzed in the paper. The prevalence of islands of information on data integration solution was given. This method can improve the integration of intelligent community and accelerate the development speed of the intelligent community.