A Double-Octagon Fractal Microstrip Yagi Antenna (D-OFMYA) which is aimed to cover unlicensed frequency of 5.8 GH is presented in this paper. The primary purpose of this experiment is to enhance gain of conventional microstrip antenna. The proposed antenna built on Arlon CuClad 217 substrate with thickness of 0.787 mm and dielectric permittivity of 2.2. A 3D full-wave EM simulator was used to design and to simulate the antenna. A computerized simulation model of the proposed antenna showed that the antenna is able to generate a maximum gain of 14.49 dB with S₁₁ of -24.2 dB in a surface size of 80 mm x 120 mm. By contrast, results of an experiment indicated the fabricated D-OFMYA can reach a gain as high as 14 dB with the value of S₁₁ is -19.8 dB. It can be concluded that a nominal gain of the D-OFMYA comes in higher than other microstrip Yagi array antennas and size reduction can be achieved through this design.

A two-step method is proposed to estimate the direction-of-arrivals (DOAs) of quasi-stationary source signals, with a partlycalibrated uniform linear array (PC-ULA). The special structure of Toeplitz matrix is utilized to estimate the sensors' uncertainties. Then, a Khatri-Rao (KR) based multiple signal classification (MUSIC) algorithm is proposed to estimate the DOAs of source signals. Simulation results show that the proposed method renders lower root-mean-square-error (RMSE) than existing KR-based ESPRIT algorithms, especially under low signal-to-noise-ratio (SNR) and small angle separation between DOAs. It is also shown that the proposed method increases the degree-of-freedom (DOF) by one, as compared to the counterpart ESPRIT methods.

For energy harvesting applications a new design of a coplanar waveguide (CPW) fed monopole antenna is presented. It covers almost all useful band ranges from 900 MHz-9.9 GHz (Radio, GSM, ISM, UWB bands). It also provides band reject characteristics for the range 3.1 GHz-5.6 GHz (HIPERLAN, C-Band, and W-LAN) to avoid interference from this range. The new design is based on the modification of coplanar waveguide (CPW) structure and optimizing the gap between patch and CPW ground for covering the ultra wideband (UWB) range and other useful ranges (Radio, GSM and ISM). Bandwidth enhancement and impedance matching for UWB range have been obtained by chamfering the corners, cutting two slots in CPW ground and dual stubs. The new design incorporates a parasitic patch above the antenna patch for tunning the desired band rejection. The entire design has been optimized at various stages during its evolution. The structure is compact in size 50×40×1.6 mm³. It may also be used for mobile, military and satellite applications.

The design of hexadecagon circular patch (HDCP) antenna for dual band operation is presented In this paper. The proposed antenna operates at two resonating frequencies 13.67 GHz, 15.28 GHz with return loss of -42.18 dB, -38.39 dB, and gain 8.01 dBi, 6.01 dBi respectively. An impedance bandwidth of 854 MHz (13.179-14.033 GHz) and 1140 MHz (14.584-15.724 GHz) is observed for dual-bands respectively. To produce the circular polarization, the HDCP antenna is incorporated with ring and square slots on the radiating patch. The defected ground structure (DGS) is considered for enhancement of gain. The proposed antenna, axial ratio is less than 3 dB and VSWR ≤ 2 for dual bands. The measured and simulated (HFSS, CST) results of of the HDCP antenna are in agreement. The HDCP antenna has work at Ku band for satellite communications.

This paper presents two novel miniaturized broadband Quasi-Yagi antennas which adopt compact layouts and two different modified bowties as driven dipoles. In these antennas, the microstrip feed and λ/4 impedance transformer are placed horizontally and rearranged in a same horizontal line with balun to reduce the vertical size. The horizontal size is reduced by loading the vertical metallic strips at the sides of bowtie driven dipole and ground patch. Compared with the conventional Quasi-Yagi antenna, the sizes of the two proposed antennas are decreased to approximately 50%. The experiment results exhibit that they have wide bandwidths of 2.27-3.35 GHz and 2.14-3.3 GHz for reflection coefficient below -10 dB. Their gains reach 4dBi over the operation frequency band, which indicate that they can be applied conveniently in wireless communications and recognition fields like WLAN, RFID, WiMAX and LTE frequency bands.

In this letter, an electrically-small circularly polarized (CP) quasi-Yagi antenna is presented. It is composed of three elements; i.e., a compact single-feed crossed-dipole antenna acted as the driver and two parasitic elements acted as the reflector and director, respectively. Each arm of all elements contains a meander line with an arrowhead ending to realize compactness. The driver has double vacant-quarter printed rings incorporated into it to generate the CP radiation. The parasitic elements are incorporated with the crossed-dipole driver to not only produce a directive radiation, but also broaden the antenna bandwidth. The final design with overall size of 35 mm×35 mm×27 mm (0.184λ_o×0.184λ_o×0.142λ_o at 1.575 GHz, ka = 0.93) a measured 10-dB bandwidth of 19.23% (1.476-1.790 GHz), 3-dB axial ratio bandwidth of 7.67% (1.505-1.625 GHz), a broadside gain of 3.0 ± 0.2 dBic, and the maximum front-to-back ratio of 8.2 dB. The proposed antenna is applicable to a variety of wireless system operating near 1.575 GHz, such as Global Positioning Systems, Global Navigation Satellite Systems, as well as international maritime satellite organization (Inmarsat) networks.

In this study, a new slot embedded microstrip antenna for dual-band dual-polarization operation is proposed. The antenna comprises a single layer structure with a square radiating patch where the feed port is located along a diagonal line of the patch. Two narrow slots parallel and close to the radiating edges of the patch are loaded on the patch. Patch without slots is resonated for X-band and another resonant frequency at Ku-band is obtained by loading the slots. Moreover, the loading of slots helps to produce two orthogonal modes of equal amplitudes at X-band. Furthermore, the feed port along the diagonal line of the square patch makes it possible to radiate dierent polarization at the two bands. The antenna can radiate circular and linear polarization at X- and Ku-band, respectively. Current distributions of the antenna at both bands are observed to explain the behavior of the antenna and conrm the polarization characteristics at X- and Ku-band. A 3-dB axial ratio bandwidth of 1.35% is achieved. Measured gains of 6.60 dBic and 5.80 dBi with good radiation performances are achieved at X- and Ku-band, respectively. Moreover, good measured cross-polarization levels of 27.6 dB at X-band and 15.6 dB at Ku-band are obtained. The measured performances of the fabricated antenna are consistent with simulated results.

Frequency selective surfaces (FSS) lter specific electromagnetic (EM) frequencies that are defined by the geometry and often fixed periodic spacing of a conductive element array. By embedding the FSS pattern into an origami structure, we expand the number of physical configurations and periodicities of the FSS, allowing for fold-driven frequency tuning. The goal of this work is to examine the fold-dependent polarization and frequency behavior of an origami-inspired FSS under normal incidence and provide physical insight into its performance. The FSS is tessellated with the Miura-ori pattern and uses resonant length metallic dipoles with orthogonal orientations for two primary modes of polarization. A driven dipole model with geometric morphologies, representative of the folding operations, provides physical insight into the observed behavior of the FSS. Full-wave simulations and experimental results demonstrate a shift in resonant frequency and transmissivity with folding, highlighting the potential of origami structures as an underlying mechanism to achieve fold-driven EM agility in FSSs.

Current phones include more metal than earlier, which deteriorates the performance of antennas. This paper presents the first complete antenna set designed for a modern handset with a full metal back cover. 4G, Wi-Fi, and GPS antennas are integrated into the metallic side frame of the device in a realistic model. The designed antennas are either capacitive coupling elements with reactive loads or slot antennas. Fixed matching circuits are used to improve total efficiency. The passive implementation enables the use of carrier aggregation (CA) to increase the data rates, and includes also the multiple-input multiple-output (MIMO) operation for 4G and Wi-Fi. The designed antennas cover frequency bands 704--960 MHz, 1.56--1.61 GHz, 1.71--2.69 GHz, 2.4--2.484 GHz, and 5.15--5.875 GHz, producing in measurements a good agreement with simulation results.

A wide half-power beamwidth antenna based on magnetic coupling in near-field (NF) regions and circular polarization (CP) in far-field (FF) is proposed for RFID multiservice applications in UHF band. The prototype consists of a cross-strip and an L-shaped strip on the top layer, fed by an F-shaped network on the bottom layer. CP electromagnetic wave is radiated by the cross-strip, and the antenna also simultaneously brings opposite directed currents (ODC) to generate strong magnetic field in near-field region. Half-power beamwidth is 100˚ in xoz-plane and 102˚ in yoz-plane, which can be used to scan for large regions. An 88 × 88 × 1.6 mm³ antenna has been fabricated on an FR-4 substrate to fit RFID applications. Measured tests on read range by observing feedback received signal strength indication (RSSI) values are carried out, exhibiting 100% read rate for near-field tags within 25 mm and exciting read distance for far field tags up to 1 m for large reading region of 170 × 170 mm².

The study and design of a wideband aperture coupled microstrip patch array is presented. The proposed design considers the 2.4 to 3 GHz frequency range but may be adapted to other frequencies. A 16 element planar array of the size of about 400 mm by 400 mm by 12.5 mm provides measured gain between 15.4 to 16.8 dBi and Side-Lobe Level (SLL) between 15.3 to 20.7 dB without a reflector within the 2.4 to 3 GHz frequency range. With a reflector significant increase in F/B is obtained but at the expense of higher SLL.

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 this paper, a single band-notched at 5.2 GHz with complementary split ring resonator (CSRR) ultra-wideband (UWB) antenna and its implementation in designing of two element multiple-input multiple-output (MIMO) with high and uniform isolation are experimentally demonstrated. The proposed UWB MIMO consists of T-shaped stub in ground plane in between antenna elements of the size of λ_{at 3.1 GHz/4} to achieve minimum 20 dB isolation, which is almost uniform in entire UWB band. The size of the UWB MIMO antenna is 0.31λ_{at 3.1 GHz}×0.434λ_{at 3.1 GHz}×0.008λ_{at 3.1 GHz} mm³ and it is printed on RT/duroid 5880 substrate (ɛ_r = 2.2, tanδ = 0.0009), which leads to good gain and high total efficiency of the antenna in operating bands. The simulated and measured result shows good agreement for the impedance bandwidth (|S₁₁| < -10 dB) and isolation (|S₂₁| < -20 dB) most of the operating band, excluding the notched band at 5.2 GHz in UWB range. The simulated, measured and calculated MIMO antenna diversity parameters proves that the antenna is suitable for UWB MIMO systems.

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 the 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 solves the problem of minimizing losses in the stator magnetic core of high-speed electric machines with the use of amorphous iron. A fundamentally new technology for manufacturing of a stator magnetic core from segments of amorphous steel is developed by the authors. The feature of the new stator design is the possibility to use technological ducts located inside the stator as cooling ducts. This aspect significantly improves the heat dissipation from the active zone of the stator and, accordingly, minimizing temperature. The efficiency of this solution was studied using two power generators of 100 kW and 200 kW and rotational speeds of 60,000 rpm and 45,000 rpm respectively in the software complex Ansys Maxwell. Harmonic compositions of currents and voltages, flux density distributions in active elements of the generator in various operating modes were studied: under load, in a three-phase short-circuit and at idle. Also, the obtained data were compared with analogous models of an electrogenerator made of electrical steel. The results of the study showed the operability and effectiveness of the proposed technology. Based on the results of the research, a prototype of the stator magnetic core made from amorphous iron was created. Losses in the generator were experimentally measured. Also the results of experimental studies of aerodynamic losses are presented.

This paper presents a broadband switchable 3D structure, which can be used to protect the information equipment from high intensity microwave wave. Compared to other defending designs, the proposed structure in this paper has wider working band. When the amplitude of incident wave within working band is low, the structure would allow them to pass with little loss. As the amplitude of incident wave is high enough to activate diode, the wave would be reflected. The Full-wave simulations are performed in CST to analyze the transmission performance. The simulated results verify the transmission performance and defending function. Its working principle is explained through change of the effective material parameters at two states. A prototype is fabricated. The protection property of the structure as a function of intensity of incident wave is verified in waveguide simulator.

A research of millimeter wave high order frequency multiplier based on the fierce inductive nonlinearity of avalanche diode is presented. The operation of high order frequency multiplication is introduced, and the high order harmonics generation character under external RF field modulation is analyzed. The characteristc of multiplier circuit is also discussed. Maximum output power of 6 mW and minimum conversion loss of 17 dB are obtained at output frequencies of 94 GHz and 96 GHz with 15th multiplication order. The phase noise of output 94 GHz signal is about -90 dBc/Hz and -94.33 dBc/Hz at 10 kHz and 100 kHz offset.

This communication presents a novel compact and wideband circularly polarized (CP) slot antenna fed by microstrip feedline. The proposed antenna consists of a corner-truncated square-ring slot patch and a novel bent strip. The CP radiation is formed by using the bent strip to excite CP resonance modes. By intruding several open stubs to the corners of the square-ring slot patch, the impedance matching and axial ratio (AR) bandwidth are improved. The measured results show that the proposed antenna has the advantage of wideband characteristics in terms of an impedance bandwidth of 90.59% (3.2-8.5 GHz) and 3-dB axial ratio bandwidth of 84.2% (3.3-8.1 GHz). The principle as well as simulated and measured results of the proposed antenna is revealed.

This paper presents designs of novel E-plane spiro meander line uniplanar compact electromagnetic bandgap (E-SMLUC-EBG) and H-plane spiro meander line uniplanar compact electromagnetic bandgap (H-SMLUC-EBG) structures. The proposed EBG has been applied in mutual coupling reduction of a dual-element multiple input multiple output (MIMO) antenna system for WLAN by placing an EBG structure between the radiating antennas. Compact size of EBG helps in reducing the edge to edge distance between Antennas that is 0.14λ₀ in this case, and it increases the compactness of integrated circuit. We get 19 dB and 11 dB simulated mutual coupling reduction in E-plane and H-plane respectively at 5.8 GHz. Measured isolation improvement of 20.3 dB for E-plane and 14.7 dB for H-plane has been achieved. This coupling reduction is also confirmed by surface current and correlation coefficient plots. The four-element (2×2) MIMO antenna system with proposed EBG is also simulated.

Permanent magnet linear synchronous motors (PMLSM) are well known for its high thrust performance. However, such high thrust can be distorted by the existence of cogging force due to the attraction between stator core and permanent magnet (PM). To improve its performance, two parts of the PMLSM structure were considered during the design. They are PM magnetization arrangement on mover side and stator slot opening parameters on stator side. The designed models were simulated by using FEM software, and the performances of the models are then compared. The aim of the design is to achieve high thrust and low cogging force characteristics. Apart from average thrust F_ave and cogging force F_cog, the performance of the PMLSM is also evaluated using average thrust, F_ave to cogging force ratio F_cog, called as thrust ratio. Based on the design, the highest thrust ratio F_ave: F_cog, obtained from radial, axial and Halbach models, are 2.5032, 2.6262 and 1.8437, respectively.