A compact eight-element frame antenna array covering the 5G n79 frequency band (4.4–5.0 GHz) has been proposed in this paper. Considering the demands in the application of 5G ultrathin smartphones, the antenna unit has been miniaturized and designed with a low profile. Each antenna unit occupies a distance of 11.1 mm on the long edge, and the profile height of each unit is only 3 mm. The antenna array consists of 8 identical monopole antennas. By loading an inverted E-shaped slot on the ground plane and arranging the positions of the antenna units reasonably without the need for a decoupling structure, the antenna can achieve a low profile and compact design. Simultaneously, it can achieve excellent isolation and cover the entire n79 frequency band. The processed eight-element antenna array has a −6 dB bandwidth ranging from 4.38 to 5.19 GHz. The isolation between all antennas is better than −13.9 dB. The total efficiency is between 48.66% and 90.57%, with an average efficiency of 68.6%. The ECC (envelope correlation coefficient) is less than 0.066. The antenna array is characterized by its small size, low profile, simple structure, easy manufacturing, and excellent radiation performance. It holds significant application value in the design of MIMO antennas for 5G ultrathin smartphones.
Dynamic metasurface antennas (DMAs) and dynamic antenna arrays (DAAs) are emerging concepts in low-profile antenna design, providing alternative structures with lower circuit complexity and power requirements for radar and communication systems. However, dynamic antennas are prone to significant grating lobe and beam fixation problems due to their discrete amplitude and phase control. The reasons behind these issues are explored through mathematical and simulation analysis of three specific cases, and solutions are subsequently proposed and partially experimentally verified.
Brahim Fady, Jaouad Terhzaz, Abdelwahed Tribak
et al.
The article introduces a new, low-cost, integrated, multiband antenna design intended for wristbands and wearable wireless devices (WWD). With a miniaturized planar square-shape sizing 29 × 29 mm2, the antenna can fit easily inside WWDs. The proposed design covers the most used frequency bands such as LTE2300, ISM2400, LTE2600, WiMAX3500, WiMAX5200, and ISM5800 in which the antenna reaches up to −25 dB and 6.9 dBi in terms of S11 and gain, respectively. To evaluate the exposure amenability of design on human body, we studied the specific absorption rate (SAR) of the design in two main use cases: multilayered human wrist model and a SAM (Specific Anthropomorphic Mannequin) head model. In each use case, the SAR results in different positions for all frequencies are compared to FCC standards.
Cédric Aurélien Matsaguim Nguimdo, Emmanuel D. Tiomo
Résumé:
En télédétection, il existe un grand nombre d'algorithmes permettant de classifier une image satellite. Parmi ces algorithmes de classification, la Forêt d'Arbres Aléatoires apparait comme particulièrement performant. Cette étude a pour objectifs d'évaluer (1) l'importance de la sélection des images pour le niveau de précision du modèle d'entrainement et (2) la nature de la relation qui existe entre le niveau de précision du modèle et celui de la précision globale de la carte thématique résultant de la classification de l'image satellite avec cet algorithme de classification. A partir d'une image Landsat 8 OLI prise au-dessus d'une zone de montagne tropicale : la région de l'Ouest Cameroun, 35 modèles ont été construits et testés. Les résultats montrent que le niveau de la précision globale des résultats de la Forêts d'Arbres Aléatoires est étroitement dépendant d'une part de la précision du modèle d'entrainement utilisé pour classifier l'image satellite, et d'autre part du choix des images utilisées pour entrainer ce modèle. De plus, la sélection de ces images est elle-même dépendante de la qualité des zones d'entrainement qui serviront à la construction du modèle. Il est donc important de mettre en accent particulier sur la qualité des données d'entrée afin de garantir des résultats satisfaisants avec cet algorithme.
Mots clés : Forêt d’Arbres Aléatoires ; précision ; modèle d’entrainement ; télédétection ; Cameroun
Instruments and machines, Applied optics. Photonics
<p><em>Technological advancement comes with both positive and negative impacts to the society, including the cybercrime. The main problems discussed in this study is regulation of criminal acts of scams committed through electronic media, particularly SMS, as well as the efforts to handle such crime in accordance with applicable legal provisions, both based on the Criminal Code and based on Law Number 11 of 2008 on Electronic Information and Transactions that has been amended by Law no. 19 of 2016. This study applies the Normative Legal Research method. The results showed that the criminal act of scams committed online was in principle similar to that of conventional fraud, the only difference being the means of action, namely using an electronic system, namely computers, the internet, or cellular telecommunication devices. Based on the prevailing legal provisions, online fraud can be treated similar to that conventional offenses stipulated in the Criminal Code (KUHP), so that the case handling process is also based both on the Criminal Code and Electronic Information and Transactions law</em></p>
In this paper, pattern synthesis through time-modulated linear array is studied, and a novel strategy for harmonic beamforming in time-modulated array is proposed. The peak side lobe level is designed as optimization objective function, and the switch-on time sequence of each element is selected as optimization variable. An improved invasive weed optimization (IWO) algorithm is developed in order to determine the optimal parameters describing the pulse sequence used to modulate the excitation weights of array elements. Representative results are reported and discussed to point out potentialities and advantages of the proposed approach, which can obtain lower objective function values.
Eduardo A. M. Souza, Phelipe S. Oliveira, Adaildo G. D’Assunção
et al.
This paper presents a social spider optimization (SSO) design of a small-size microstrip antenna. Two antenna miniaturization techniques, based on the use of a Koch fractal contour and a shorting post (connecting the patch to the ground plane), are combined to enable a major size reduction. The antenna is inset fed by a microstrip line. The developed SSO algorithm is used to find out the best radius and position of the shorting post and the length of the inset feed, to achieve the desired resonant frequency with good impedance matching. Antenna prototypes have been fabricated and measured. The good agreement obtained between numerical simulation and experimental results has validated the design procedure. Compared with a conventional rectangular patch, the antenna resonance frequency is reduced from 2.45 GHz to 730 MHz, which corresponds to a remarkable miniaturization of about 70%. The proposed antenna is suitable for applications in the 700-800 MHz frequency range, such as 4G mobile communication systems.
In this paper, a new CS-FMM method that conjugates compressive sensing (CS) with the fast multipole method (FMM) is proposed and validated to efficiently solve monostatic scattering from an arbitrary conducting target. The far zone scattered fields are viewed as the signal of interest. CS is introduced to reduce the number of computations. A new set of incident sources has been generated according to CS. By solving the matrix equations under the new set of incident sources and calculating the related far zone scattered fields, the measurements of the aforementioned signal can be derived. Then, the CS inversion is employed to reconstruct the desired monostatic far zone scattered fields by finding the smallest possible ℓ1 norm solution. Monostatic radar cross section (RCS) from several conducting targets is studied by CS-FMM and by the traditional FMM. And the results are compared with each other to illustrate the accuracy and efficiency of the proposed method.
A symmetrically crossed-loop antenna featuring very high radiation efficiency across the entire LTE frequency bands for metal-rimmed smartphones with only 2 mm ground clearance is proposed, analyzed, and verified. The employment of even and odd modes is utilized to achieve wide bandwidth across 698–960 MHz (low-frequency spectrum), 1710–2170 MHz (middle-frequency spectrum), and 2300–2690 MHz (high-frequency spectrum). Empirical analysis confirms the crossed-loop topology results in a 180° phase shift of the electric current distribution on the ground plane, resulting in enhancement of the radiation resistance. As a result, the devised LTE antenna exhibits more than 48% to 75% total system efficiency across the entire band of interest, which is the highest efficiency reported in literature for metal-rimmed smartphones with extremely small ground clearance.
Famara Hyacinthe Sanou, Frédéric Le Roy, Devi R. Gnyawali
This research examines how a firm's position in a coopetitive network (formed through cooperation among firms within an industry) influences the extent of the firm's competitive aggressiveness and market performance. The authors collected data on the competitive and cooperative actions of firms in the mobile telephone industry from 2000 to 2006, using structured content analysis of news reports. The results show that the centrality of a firm in a coopetitive network contributes to the firm's competitive aggressiveness through increased volume and variety of competitive actions. Further, the more central a firm is in the network, the greater is its market performance. Firms that undertake more volume and variety of competitive actions improve their market performance. Overall, these results show that being in a central position in a coopetition network is quite advantageous for the firm.
Henna Paaso, Aki Hakkarainen, Nikhil Gulati
et al.
Reconfigurable antenna systems have gained much attention for potential use in the next generation wireless systems. However, conventional direction-of-arrival (DoA) estimation algorithms for antenna arrays cannot be used directly in reconfigurable antennas due to different design of the antennas. In this paper, we present an adjacent pattern power ratio (APPR) algorithm for two-port composite right/left-handed (CRLH) reconfigurable leaky-wave antennas (LWAs). Additionally, we compare the performances of the APPR algorithm and LWA-based MUSIC algorithms. We study how the computational complexity and the performance of the algorithms depend on number of selected radiation patterns. In addition, we evaluate the performance of the APPR and MUSIC algorithms with numerical simulations as well as with real world indoor measurements having both line-of-sight and non-line-of-sight components. Our performance evaluations show that the DoA estimates are in a considerably good agreement with the real DoAs, especially with the APPR algorithm. In summary, the APPR and MUSIC algorithms for DoA estimation along with the planar and compact LWA layout can be a valuable solution to enhance the performance of the wireless communication in the next generation systems.
This paper proposes a new design technique for internal antenna development. The proposed method is based on the framework of topology optimization incorporated with three effective mechanisms favoring the building blocks of associated optimization problems. Conventionally, the topology optimization of antenna structures discretizes a design space into uniform and rectangular pixels. However, the defining length of the resultant building blocks is so large that the problem difficulty arises; furthermore, the order of the building blocks becomes extremely high, so genetic algorithms (GAs) and binary particle swarm optimization (BPSO) are not more efficient than the random search algorithm. In order to form tight linkage groups of building blocks, this paper proposes a novel approach to handle the design details. In particular, a nonuniform discretization is adopted to discretize the design space, and the initialization of GAs is assigned as orthogonal arrays (OAs) instead of a randomized population; moreover, the control map of GAs is constructed by ensuring the schema growth based on the generalized schema theorem. By using the proposed method, two internal antennas are thus successfully developed. The simulated and measured results show that the proposed technique significantly outperforms the conventional topology optimization.
Planar metamaterials (MTMs) with low refractive index are proposed as a cover in a high-gain patch antenna array configuration. This MTMs array antenna has the following features: the number of array elements significantly decreases compared with the conventional array; the elements spacing is larger than a wave length by far; the feeding network is simpler. MTMs are made of two layers of periodic square metallic grids and placed above the feeding array. With the same aperture size, the directivity of MTMs-cover antenna array is higher than the conventional antenna array. The simulation results show that an array of 2 × 2 patch elements integrated with MTMs yields about 26 dB of directivity which is higher than that of conventional 8 × 8 patch array. Furthermore, on the condition of the same aperture size, an array patch with 4 × 4 elements integrated with the MTMs-cover has an equivalent gain compared with the conventional patch array with 16 × 16 array elements. Obviously, the former has a simpler feeding network and higher aperture efficiency. The experimental work has verified that the 2 × 2 array case and the measured results have good agreement with the simulation.
This paper proposes a novel microwave continuous adjustable band-pass filter integrated power divider based on nematic liquid crystals (LCs). The proposed power divider uses liquid crystal (LC) as the dielectric material. It can realize phase shift by changing the dielectric anisotropy, when biasing the high anisotropy nematic liquid crystal. It is mainly used in microwave frequencies. It has a large number of advantages compared to conventional filter integrated power divider, such as low loss, multifunction integration, continuous adjustable, miniaturization, low processing costs, low operating voltage, high phase shift, and convenient manufacture. Therefore, it has shown great potential for application.
V. S. S. S. Chakravarthy Vedula, S. R. Chowdary Paladuga, M. Rao Prithvi
Sidelobe level suppression is a major problem in circular array antenna (CAA) synthesis. Many conventional numerical techniques are proposed to achieve this which are time consuming and often fail to handle multimodal problems. In this paper, a method of circular array synthesis using nature inspired flower pollination algorithm (FPA) is proposed. The synthesis technique considered here adapts one and two degrees of freedom, namely, amplitude only and amplitude spacing. The effectiveness of the FPA is studied by comparing the results with genetic algorithm (GA) and uniform circular array antenna (UCAA) with uniform spacing. Also the effect of additional degree of freedom on the aperture size and the computational time is analyzed. A relative side lobe level (SLL) of −25 dB is achieved using the algorithm under both no beam scanning (0°) and beam scanning (15°) conditions for 20 and 40 elements of CAA.
H. Abou Taam, G. Zakka El Nashef, M. Salah Toubet
et al.
This paper is dedicated to different experimental validations concerning a novel concept of beam forming and beam steering antenna. The working principle of the antenna is based on the equivalent radiating surface approach and inspired from an electromagnetic band gap antenna. The theoretical aspect and some numerical validations have been already published in the work of Abou Taam et al. (2014). Different electromagnetic behaviors have been demonstrated, such as low mutual coupling, and high gain preservation for high scanning angles values. In this paper, some of these electromagnetic behaviors will be proven experimentally by the means of two different feeding configurations.
This paper presents a novel leaky-wave antenna based on the Half-Mode Substrate Integrated Waveguide (HMSIW) structure with low side lobe level. The effect of the structural parameters of the LWAs on the radiation performances is studied. Using beam-forming technique, the leakage loss factor α along the radiation aperture is designed in a tapered way by controlling the aperture depth along the structure. This controls the radiated power along the antenna aperture and finally achieves the radiation pattern with low SLL. Furthermore, the antenna structure is optimized to get an even lower SLL.