Propagation of Surface Wave Along a Thin Plasma Column and Its Radiation Pattern

Propagation of the surface waves along a two-dimensional plasma column and the far-field radiation patterns are studied in thin column approximation. Wave phase and attenuation coefficients are calculated for various plasma parameters. The radiation patterns are shown. Results show that the radiation patterns are controllable by flexibly changing the plasma length and other parameters in comparison to the metal monopole antenna. It is meaningful and instructional for the optimization of the plasma antenna design.

Phase Compensation of Composite Material Radomes Based on the Radiation Pattern

Some compensation methods have been pro- posed to mitigate the degradation of radiation characteris- tics caused by composite material radomes, however most of them are complex and not applicable for large radomes, for example, the modification of geometric shape by grinding process. A novel and simple compensation strat- egy based on phase modification is proposed for large reflector antenna-radome systems. Through moving the feed or sub-reflector along axial direction opportunely, the modification of phase distribution in the original aperture of an enclosed reflector antenna can be used to reduce the phase shift caused by composite material radomes. The distortion of far-field pattern can be minimized. The modification formulas are proposed, and the limitation of their application is also discussed. Numerical simulations for a one-piece composite materials sandwich radome and a 40 m multipartite composite materials sandwich radome verify that the novel compensation strategy achieves sat- isfactory compensated results, and improves the distortion of the far-field pattern for the composite material radomes. For one-piece dielectric radome, more than 60% phasedifference caused by radome is reduced. For multipartite radome, the sidelobe level improves about 1.2 dB, the nulling depth improves about 3 dB. The improvement of far-field pattern could be obtained effectively and simply by moving the feed or sub-reflector according to phase shift of the radome.

Tunable acoustic radiation pattern assisted by effective impedance boundary

The acoustic wave propagation from a two-dimensional subwavelength slit surrounded by metal plates decorated with Helmholtz resonators （HRs） is investigated both numerically and experimentally in this work. Owing to the presence of HRs, the effective impedance of metal surface boundary can be manipulated. By optimizing the distribution of HRs, the asymmetric effective impedance boundary will be obtained, which contributes to generating tunable acoustic radiation pattern such as directional acoustic beaming. These dipole-like radiation patterns have high radiation efficiency, no finger- print of sidelobes, and a wide tunable range of the radiation pattern directivity angle which can be steered by the spatial displacements of HRs.

Dual-Channel Communication of Column Plasma Antenna Excited by a Surface Wave——Actualization and Simulation of Radiation Pattern

Along with the introduction of the concept of dual-channel communication,we utilized the finite-difference time-domain（FDTD） method to simulate and measure the radiation pattern under certain plasma densities and plasma collision frequencies.Results show that under certain settings,the radiation pattern of a plasma antenna resembles that of a metallic antenna.In contrast to a metallic antenna,a plasma antenna possesses other functionalities,such as dynamic reconfiguration and digital controllability.The data from simulation are similar to the measurement results,indicating that column plasma antenna can realize dual-channel communication.This work confirms the viability of realizing dual-channel communication by column plasma antenna,which adds a new but promising method for modern intelligent communication.

Radiation pattern analyses of circular aperture antenna to generate radio orbital angular momentum

Circular aperture antenna recently has been regarded as a nature source to generate high power radio orbital angular momentum （OAM） in millimeter （mm） wave; however, the radiation pattern was not investigated. Theoretical derivation of radiation pattern of circular aperture OAM antenna is conducted to evaluate the performance. Extensive simulations verify the validity of the theoretical result. Furthermore, performance of such antenna excited by orthogonal TE and TM modes is compared, which shows the potential application for TEgl mode to create pure OAM g-1 mode in a practical system, providing guidance for generation of twisted radio waves in mm-wave bands.

Feedline Separation for Independent Control of Simultaneously Different Tx/Rx Radiation Patterns

The shortcoming of Wi-Fi networks is that one user can access the router at a time.This drawback limits the system throughput and delay.This paper proposes a concept of Simultaneously Different Tx/Rx(SDTR)radiation patterns with only one antenna set at the router.Furthermore,these two patterns have to be simultaneously operated at the same time so that the system delay can be eased.An omni-directional pattern is employed at router for receiving mode so that the router can sense carrier signal from all directions.At the same time,the router launches a directional beam pointed to another user.A proposed circuit allows these two modes to be able to operate the same time.To evaluate the SDTR concept,a prototype is constructed for testing in real circumstance comparing to computer simulation.As a result,the SDTR concept can improve the system throughput while decreasing the system delay comparing to conventional system.

Reconstruction of Antenna Radiation Pattern Based on Compressed Sensing

The measurement of the far-field radiation pattern is an important factor in describing the character-istics of the antenna.The measurement process is time consuming and expensive.Therefore,this paper proposes a novel method to reduce the number of samples required for radiation pattern measurement by adopting com-pressed sensing theory.This method reconstructs the radiation pattern from data measured by a few sensors,and the positions of these sensors are generated via the m-sequence.Simulation results demonstrate that the proposed algorithm can effectively reconstruct the complete radiation pattern by using the 50%samples.

Seismic moment tensor representations and radiation patterns in unbounded media with elipsoidal cavities driven by low frequency pressure

Seismic waves generated in elastic media by ellipsoidal cavities driven by low frequency pressure can be solved by Eshelby′s method. In this paper we prove that this method, originally presented for elastostatic ellipsoidal inclusion problems, can also be applied to dynamic problems on the assumption that wavelengths are much longer than the dimensions of cavities. Comparison between the approximate solution for spherical cavities and its relevant precise solution shows that this method may be used for radii of cavities smaller than 100 m and for frequencies below 10 Hz. By this approach we show that, for low frequency seismic waves in the far field an explosive load on an ellipsoidal cavity can be equivalent to three dipoles oriented along the principal axes of that cavity. Seismic radiation patterns are given analytically and results thus obtained show that an explosion detonated in an ellipsoidal cavity may radiate significant S waves.

A Generalized Array Factor for Time-Modulated Hexagonal Based Antenna Array Geometry With Novel Trapezoidal Switching

The concept of the time-modulated array has been emerging as an alternative to the complex phase shifters,which lowers the cost of the array feeding network due to the utilization of radio frequency(RF)switches.The various forms of hexagonal antenna array geometries can be used for applications like surveillance tracking in phased array radar and wireless communication systems.This work proposes the generalized array factor(AF)for the hexagonal antenna array geometry based on time modulation.The time modulation in generalized hexagonal geometry can maintain the fixed static amplitude excitation,giving more flexibility over time.Furthermore,a novel trapezoidal switching function is also proposed and applied to the generalized array factor to enable future researchers to use this array factor in the field of advancement to observe how switching schemes like trapezoidal and rectangular affect the array pattern's side lobe level(SLL).The generalized equation can be utilized for the analysis and synthesis of radiation characteristics of the time-modulated hexagonal array(TMHA),time-modulated concentric hexagonal array(TMCHA),time-modulated hexagonal cylindrical array(TMHCA),and time-modulated hexagonal concentric cylindrical array(TMHCCA).The numerical result illustrates the generation of AF of time-modulated hexagonal structures and also shows that the trapezoidal switching sequence outperforms the rectangular switch using the cat swarm optimization(CSO)approach.

Pattern synthesis optimization of 3-D ODAR based on improved GA using LSFE method

Pattern synthesis in 3-D opportunistic digital array radar(ODAR) becomes complex when a multitude of antennas are considered to be randomly distributed in a three dimensional space.In order to obtain an optimal pattern,several freedoms must be constrained.A new pattern synthesis approach based on the improved genetic algorithm(GA) using the least square fitness estimation(LSFE) method is proposed.Parameters optimized by this method include antenna locations,stimulus states and phase weights.The new algorithm demonstrates that the fitness variation tendency of GA can be effectively predicted after several "eras" by the LSFE method.It is shown that by comparing the variation of LSFE curve slope,the GA operator can be adaptively modified to avoid premature convergence of the algorithm.The validity of the algorithm is verified using computer implementation.

OPTIMIZATION ON ANTENNA PATTERN OF SPACEBORNE SAR WITH IMPROVED NSGA-Ⅱ

Optimization of antenna array pattern used in a spaceborne Synthetic Aperture Radar (SAR) system is considered in this study. A robust evolutionary algorithm, Non-dominated Sorting Genetic Algorithms (the improved NSGA-Ⅱ), is applied on a spaceborne SAR antenna pattern design. The system consists of two objective functions with two constraints. Pareto fronts are generated as a result of multi-objective optimization. After being validated by a test problem ZDT4, the algorithms are used to synthesize spaceborne SAR antenna radiation pattern. The good results with low Ambi- guity-to-Signal Ratio (ASR) and high directivity are obtained in the paper.

Radiation characteristics of ring patch antennas with capacitive feed patch

Ring patch antennas have the characteristics of electrically small size as decreasing the width of the conducting portion compared to those of conventional patch antennas.In the ring patch antenna,using capacitive feed method is suitable for impedance matching.The effect of the size of the feed patch on the input impedance of the square ring patch antennas are analyzed and radiation patterns of the square ring patch antennas are compared to that of a square conventional patch antenna by the simulated results.

A Substrate Integrated Waveguide Based Filtenna for X and Ku Band Application

In this paper Substrate Integrated Waveguide-basedfiltenna operating at Ku band is proposed.The model is designed on a low loss dielectric substrate having a thickness of 0.508 mm and comprises of shorting vias along two edges of the substrate walls.To realize a bandpassfilter,secondary shorting vias are placed close to primary shorting vias.The dimension and position of the vias are carefully analyzed for Ku band frequencies.The model is fabricated on Roger RT/duroid 5880 and the performance characteristics are measured.The proposed model achieves significant impedance characteristics with wider bandwidth in the Ku band.The model also achieves a maximum gain of 7.46 dBi in the operating band thus making it suitable for Ku-band applications.Substrate Integrated Waveguide(SIW)Structures possess most of the advantages over conventional radiofrequency waveguides since they have high power management capacity with self-consistent electrical shielding.The most noteworthy advantage of SIW,it can able to integrate all the components on the same substrate,both passive and active components.

Analytical solutions for full-field radiations of magnetoelectric antennas with nonlinear magnetoelastic coupling

This paper presents analytical solutions for full-field radiation in magnetoelectric(ME)antennas,considering a fully magnetoelastic coupled constitutive relation.A nonlinear converse ME coupling model is established,incorporating mechanical,electric,and magnetic variables with generalized Maxwell equations.This model emphasizes the essence of ME antennas,where radiation is achieved through strain/stress-mediated coupling between different phases.The magnetic flux density and electric displacement obtained from the model are used as sources to solve the full-field radiations of ME antennas.The proposed model is validated through existing experiments and simulations,demonstrating that the radiation performance of ME antennas is strongly influenced by nonlinear magneto-elastic coupling.The material parameters and magnetic bias significantly impact the magnetic flux density and far-field radiation due to the nonlinear magnetization process.The study reveals the mechanisms behind enhanced working bandwidth and frequency tuning by examining the frequency response of the radiation impedance with material parameters.By adjusting the initial magnetization rate,saturation magnetostriction,and saturation magnetization,the radiation efficiency/gain can be increased by 340%,108%,and 112%respectively.This model enhances our understanding of the full-field radiation of ME antennas and provides a foundation for designing tunable ME antennas.

Beamforming Performance Analysis of Millimeter-Wave 5G Wireless Networks

With the rapid growth in the number of mobile devices and user connectivity,the demand for higher system capacity and improved qualityof-service is required.As the demand for high-speed wireless communication grows,numerous modulation techniques in the frequency,temporal,and spatial domains,such as orthogonal frequency division multiplexing(OFDM),time division multiple access(TDMA),space division multiple access(SDMA),and multiple-input multiple-output(MIMO),are being developed.Along with those approaches,electromagnetic waves’orbital angular momentum(OAM)is attracting attention because it has the potential to boost the wireless communication capacity.Antenna electromagnetic radiation can be described by a sum of Eigen functions with unique eigenvalues,as is well known.In order to address such issues,the millimeter-wave(mmWave)communication is proposed which is considered as one of the potential technology for 5G wireless networks.The intrinsic feature of all electromagnetic waves is OAM.The OAM beams’unique qualities have led to a slew of new uses.Broadband OAM generators,on the other hand,have gotten very little attention,especially in the mmWave frequency band.The use of OAM in conjunction with mmWave can reduce the beam power loss,enhance the received signal quality,and hence increase the systemcapacity.The transmitter and receiver antennas must be coaxial and parallel to achieve precise mode detection.The proposed mmWave integrated with OAM system model is discussed in this study.The channel model is created using the channel transition characteristics.The simulation results demonstrate that the proposed system model is a good way to boost the system capacity.

A Compact Rhombus Shaped Antenna with Extended Stubs for Ultra-Wideband Applications

Ultra-wideband(UWB)is highly preferred for short distance communication.As a result of this significance,this project targets the design of a compact UWB antennas.This paper describes a printed UWB rhombusshaped antenna with a partial ground plane.To achieve wideband response,two stubs and a notch are incorporated at both sides of the rhombus design and ground plane respectively.To excite the antenna,a simple microstrip feed line is employed.The suggested antenna is built on a 1.6 mm thick FR4 substrate.The proposed design is very compact with overall electrical size of 0.18λ×0.25λ(14×18 mm2).The rhombus shaped antenna covers frequency ranging from 3.5 to 11 GHz with 7.5 GHz impedance bandwidth.The proposed design simulated and measured bandwidths are 83.33%and 80%,respectively.Radiation pattern in terms of E-field and H-field are discussed at 4,5.5 and 10 GHz respectively.The proposed design has 65%radiation efficiency and 1.5 dBi peak gain.The proposed design is simulated in CST(Computer Simulation Technology)simulator and the simulated design is fabricated for the measured results.The simulated and measured findings are in close resemblance.The obtained results confirm the application of the proposed design for the ultra-wide band applications.

Comparative Analysis on Antenna Balun and Feeding Techniques of Step Constant Tapered Slot Antenna

This paper represents the performance analysis of the different shapes of antenna balun and feeding techniques for step constant tapered slot antenna. This work also addresses the benefits of antenna balun (circular and rectangular) along with two types of feeding techniques (Microstrip line L-shape and Microstrip line I-shape). The performance of the antenna for each technique is thoroughly investigated using Computer Simulation Technology (CST) Microwave Studio software simulation under the resonant frequency of 5.9 GHz. Results demonstrate that the proposed model is an effective tool for improving antenna performance. Moreover, an extensive comparison has been carried out between the two different shapes, with and without antenna balun and between two feeding techniques focusing on return losses, gain, directivity, and voltage standing wave ratio (VSWR).

Design of Ellipse Antenna Array for Cellular Phone Localization Systems

This paper describes our contribution in the ANR (Agence Nationale de la Recherche) project called GELOCOM (GEo-LOCalisation de telephOnes Mobiles) managed by the THALES Communications company, dedicated to the emergency localization of cellular phones. This contribution takes place in the field of antennas, with the development of broad-band systems: a circular array of six elements with separated outputs for the receiving part. In this paper, we present the design and the characterization of broad-band double ellipse array antenna. This special structure is chosen in order to obtain a good omnidirectional radiation pattern, enhance the gain and maximize the V/H polarization ratio. In comparison with the already existing antenna systems in the wireless market for similar purposes, the proposed antenna has considerably shown better performance which makes it competitive among other antenna models. For the design and optimization of antennas, we use CST MWS software. The antennas have been designed and successfully measured.

Comparative Study of the Performances of Opaque and Transparent Patch Antennas

The performances of two microstrip patch antennas with low visual impact are presented in this paper and compared to an opaque solution. These consist in a copper film deposited on a Borofloat 33 glass substrate through a thin titanium gripping layer. The mesh is obtained by wet chemical etching. Antennas differ by the dimensions in the ground plane mesh pattern. The opaque antenna only consists of a full copper deposit. The transparency work was mainly carried out on the ground plane as it is the largest area available. Specific attention is paid to optical transparency in the visible light spectrum, sheet resistance and electromagnetic performances in the [2.8;3 GHz] bandwidth. They are measured in each case, compared and discussed. Both simulations and measurement results show good performance, especially the antenna with the most transparent ground plane: a high level of optical transparency of almost 73%, coupled with a sheet resistance of less than 0.028 Ohms/sq and a gain of about 3.22 dBi at 2.8 GHz, slightly higher than the gain of the reference opaque antenna of about 2.66 dBi at 2.99 GHz. The opaque reference antenna has a bandwidth of 1.30 GHz while those of the transparent antennas are about 1.60 GHz and 2.10 GHz (S11 < −10 dB). This solution presents a real interest for low cost integrated and discrete antenna solutions in ISM band.

Multi-Band Antenna with Three Folded Monopoles for Mobile Communication Systems

This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get the PMR (Professional or Private Mobile Radio) band with the GSM (Global System for Mobile Communications), DCS (Digital Cellular System) and UMTS (Universal Mobile Telecommunications System) bands. The main lobe of the antenna radiates in the zenith direction with a linear polarization over all bands. It is interesting to design the proposed antenna in order to obtain better performances in terms of directive radiation pattern (especially in the PMR band) in comparison with the already existing antenna systems in the wireless market for similar purposes. The prototype was studied with the software CST-MWS (Micro wave studio 2012). The antenna has been designed and successfully measured.