In this paper the design and implementation of a patch antenna array using Dolph Chebyshev current distribution operating in C-Band is demonstrated. The proposed novel omnidirectional triangular patch antenna array is a nonuniform array type with equal or uniform spacing between the antenna elements, but having the nonuniform amplitude excitation with Dolph-Chebyshev current distribution. Dolph-Chebyshev amplitude excitation suppresses the side lobes as well as the designed antenna works like an omnidirectional antenna. The proposed antenna array has a gain of 0.52 dB and return loss of -35.0649 dB which works as an omnidirectional antenna. This proposed antenna is suitable for C-band applications such as Wi-Fi devices, cordless phones, and keyless entry systems.

Using absorber-emitter modules, solar thermophotovoltaic (STPV) systems could potentially break through the Shockley-Queisser limit. Efficient spectral selectivity and high temperature endurance are the keys to this technology. In this paper, a high-efficiency selective absorber-emitter module based on refractory material nanostructures is designed for solar thermophotovoltaic applications. Our numerical simulations show that the proposed absorber-emitter module could provide a specified narrowband emission spectrum above the bandgap with optimal bandwidth, and its performance is robust and independent of incident angle and polarization. According to detailed balance calculations, over a broad range of module temperatures, the solar cell efficiency of our design could suprass the Shockley-Queisser limit by 41%.

A broadband circularly polarized microstrip antenna with stable phase center is proposed for multi-mode GNSS applications. The proposed antenna consists of two crossed slots on one side of PCB and a Γ-shaped microstrip feeding structure on the other side of PCB. Measurement of the designed antenna demonstrates a -10-dB impedance bandwidth of 76.7% and a 3-dB axial ratio bandwidth of 64% are realized, which cover all GPS, BeiDou, Galileo, and GLONASS bands ranging from 1.164 GHz to 1.612 GHz. In addition, stable phase center for orientation in the region above 10˚ elevation is realized for high-precision positioning. For each GNSS band, phase center variation with respect to its own mean phase center can be retained within 5˚. Over the whole GNSS bands, phase center variation with respect to the common mean phase center is retained within 6˚.

A microstrip-fed two-port multiple-input-multiple-output (MIMO) antenna has been designed for triple-band applications covering the entire ultra-wideband (UWB) with one band-notched characteristic. A defected ground structure (DGS) has been used to obtain a wideband resonance. A crescent ring has been etched on each of the two circular patch antennas to produce a band-notch characteristic centered at 5 GHz, ranging from 3.96 to 6.2 GHz. These introduce notches at 5.2/5.8 WLAN, 5.5 WiMAX, LMI C-Band and also reject the large capacity microwave relay trunk network, ranging from 4.40 to 4.99 GHz, such as in the Indian national satellite (INSAT) system operating between 4.5 and 4.8 GHz, thus making our MIMO antenna immune to many unlicensed bands. The proposed MIMO antenna elements have been isolated by more than 16 dB throughout the operating band using a modified inter-digital capacitor (MIDC) placed between the circular patch antennas. The MIDC also helps in achieving a center-band, ranging from 6.2 to 8.93 GHz, and is useful in IEEE INSAT/Super Extended C-band. The lower-band ranges from 3.08 to 3.96 GHz and covers 3.5 GHz WiMAX while the upper-band, ranging from 10 to 16 GHz, is useful for X-band and Ku-band applications. Finally, the MIMO antenna has been fabricated on an FR-4 substrate of dimensions 50×30×1.6 mm³ with a compact antenna area of 0.158λ₀². All results along with the diversity performance have been experimentally verified.

A high-order (HO) finite-difference time-domain (FDTD) method with exponential time differencing (ETD) algorithm is proposed to model electromagnetic wave propagation in Debye dispersive material in this paper. The proposed method introduces an auxiliary difference equation (ADE) technique which establishes the relationship between the electric displacement vector and electric field intensity with a differential equation in Debye dispersive media. The ETD algorithm is applied to the displacement vector and auxiliary difference variable in time domain, and the fourth-order central-difference discretization is used in space domain. One example with plane wave propagation in a Debye dispersive media is calculated. Compared with the conventional ETD-FDTD method, the results from our proposed method show its accuracy and efficiency for Debye dispersive media simulation.

In this paper, wideband high-efficiency Fresnel zone plate (FZP) reflector antennas are investigated and developed. Two simple dual-dipole unit cells with different periodicity sizes are first characterized for the design of Fresnel zone plate reflector antennas. The gain bandwidth of the FZP reflector antennas is then theoretically investigated using the two unit cells. Based on the results, a wideband high-efficiency FZP reflector containing 15 correcting zones is designed using the unit cell with a smaller size and quarter-wavelength correction phases. A standard pyramidal horn and a slot-fed patch antenna are applied to feed the FZP reflector alternately. With a feed horn, the wideband high-efficiency radiation performance including a peak gain of 32.1 dBi and an aperture efficiency of 58.2% can be achieved. By using the designed planar feeder, a compact FZP reflector antenna can be obtained with compromised radiation performance. All are demonstrated by experiments.

A broadband monopole antenna is presented, with a radiating body consisting of a fractal tree with three-dimensional conical branches. The effect on polarization and return loss of varying the number of branches, as well as the number of fractal iterations, is explored and presented. The best-case antenna, having five branches and three fractal iterations, was fabricated using a 3D-printed form covered in conductive spray paint. The return loss of this antenna was shown in both simulation and measurement to be better than -10 dB from 1.22 GHz to 24.1 GHz, a bandwidth of more than 180%.

In this article, design and analysis of a modified circular slot antenna is discussed. The proposed antenna design is attractive because of two important reasons: (i) modified circular slot creates dual operating bands; (ii) stable radiation characteristics over the operating frequency bands. The complete analysis of proposed radiator has been done on Ansys HFSS simulation software. For verifying the simulated outcomes, a prototype of antenna structure is fabricated and tested. Measured results show that the proposed antenna operates over two frequency bands i.e., 2.88-3.92 GHz and 5.26-6.28 GHz with the fractional bandwidths of 31% and 17% respectively. Experimentally measured average gain of the proposed radiator is 3 dBi and 6 dBi in lower and upper frequency bands, respectively. All these features of the proposed antenna make it appropriate for WiMAX (3.5 GHz) and WLAN (5.8 GHz) applications.

In this paper dual segment half Cylindrical Dielectric Resonator Antennas (DS h-CDRA), deploying homogenous elements, are designed and analyzed for wide-band applications. At first a single element is analyzed followed by two element DS h-CDRA. Further, Radar Cross Section (RCS) analysis is performed for different angles and frequencies. The proposed antennas are excited from the center of the ground plane using a coaxial probe feed, which results in TM_01δ as a mode of excitation in cylindrical DRA. The input impedance and radiation characteristics are determined and compared with measured results, which shows good agreement. The proposed DS h-CDRA provides measured wide bandwidth (≈ 98%) from 5.0 GHz to 11.5 GHz with gain of 4.85 dBi, and it is found constant throughout the operational band (with omnidirectional radiation pattern). The designed antennas performance has also been compared with two element h-CDRA and found even better for the same volume and effective radiation area. The RCS analysis has been performed for monostatic and bistatic mode at different frequencies and angles. The proposed antenna has been found suitable for 5.0 GHz WLAN and WiMAX wireless application.

A novel method to determine the transfer functions of power line networks is presented. Although a number of the evaluation methods have been proposed, the major drawbacks are on approximation, complexity and intuitiveness. The presented method overcomes those by making use of backward impedance transfer and forward voltage transfer techniques. Additionally, the novel method offers an extra feature that transfer functions at any points throughout the network can be simultaneously determined in one implementation. This paper first reviews some major existing methods. Then, the method of impedance and voltage transferring is derived and fulfilled with an implementation algorithm and mathematic description. Lastly, an implementation of the method on a sample network for the transfer function is demonstrated. Channel capacity is adopted as the measure for the quality of the channels.

This paper proposes a new design of reconfigurable three-sector dual-mode dual-polarized antenna for use primarily in mobile communication base stations. The design offers the flexibility to be used as a sectorial (directive) or omnidirectional base station antenna whenever required. The two different radiating modes (omnidirectional and sectorial) depend only on the excitation scenario. The proposed antenna has the advantages of offering broadband, stable radiation pattern and high polarization purity within the desired frequency band, and a simple feeding structure with a remarkable compact size (less than 800 cm³) and low profile. The achieved fractional bandwidth is 55.3% (1.7-3 GHz). The antenna design principle is validated by constructing and testing a prototype with the two modes of operation. An eight-element linear array is then constructed and synthesized as a reconfigurable base station. Results demonstrate how the design may be packaged in a compact size to offer excellent omnidirectional or sectorial performance which makes this new design an ideal candidate for reconfigurable dual-mode mobile base stations.

The paper presents a novel design technique for reflection-type varactor analog phase shifters based on tunable reflective loads. The reflective load comprises two similar tuning stubs with incorporated varactor diodes, where each varactor can be tuned independently. It is shown that by an appropriate losses equalization method applied together with a specific independent varactors control algorithm it is possible to achieve the desired 360° phase shift with stabilized losses, which are significantly lower compared to the well-known single-channel design. We derive and discuss in details main design relations arisen from the complex plane reflection coefficient consideration. The presented technique is first verified by circuit simulation in ADS, and comparison with the classical single-channel design is also considered. Next, we develop experimental prototypes of a reflective load and a full phase shifter based on a packaged silicon varactor diode for operation in C-band with 5.8 GHz central frequency. Experimental and theoretical results are in perfect agreement. Moreover, we have found that the bandwidth of the proposed phase shifter can be greatly enhanced if the reflective loads are tuned at each sub-band using a unique optimal tuning path. The suggested reflective load demonstrates the total bandwidth of 10.3% and the instantaneous bandwidth of 1.7% (sub-band), where inside each sub-band measured ripple at the central frequency is around 0.5 dB, and the maximum overall ripple is below 0.8 dB.

By combining the theory of mechanical flux-adjusting with the advantages of an interior permanent magnet synchronous machine (PMSM), a new type of auto-rotary PMs mechanical flux-varying PM machine (ARPMMFVPMM) is creatively proposed in this paper. The operation principle and mechanical flux-adjusting mechanism were deeply investigated. The relationship between deformation of spring and auto-rotary angle of gear against speed was obtained by Automatic Dynamic Analysis of Mechanical System (ADAMS). Meanwhile, the electromagnetic characteristics of the machine were numerically analyzed by Finite Element Analysis (FEA). The simulation results show that the auto-rotary of cylindrical PMs is realized by the centrifugal force of mechanical device, and the range of speed regulation is expanded by adjusting the magnetic field distribution.

The echo signal of wide-band monopulse radar spreads in multiple range cells. Thus, effective utilization of echo signal is an important issue for this kind of radar. Based on parameter estimation model, maximum likelihood method is proposed in this paper, which collects all the energy spreading in multiple range cells. Cramer-Rao low bound of angle estimation is deduced in theory. Simulation results demonstrate maximum likelihood method which performs better than both dominant scatter estimate method and weighted estimate method.

In this paper a waveguide is introduced as an absorbing modulator using GaN/AlN structure based on spherical quantum dots. The role of waveguide (modulator) dimensions on optical profile of light in the channel and coupling efficiency is also investigated. These parameters can affect the main characteristics of modulator like absorption and depth of modulation. First we will give a brief explanation about the all optical modulator structure based on spherical quantum dots and its optical properties. Then the electrical fields in optical fiber and modulator will be introduced, and the effects of dimensions on these fields will be discussed. The results show that the electric field distribution determines the insertion loss and also effects on modulation. Finally we will determine the proper dimensions of modulator for coupling to optical fiber.

By analyzing the characteristics of the super low frequency (SLF) electromagnetic wave in through the earth (TTE) communication, an orthogonal array of magnetic antenna is proposed for receiving SLF signal, and a new robust adaptive beamformer is used to process the received signals. The proposed beamformer is a multi-input generalized sidelobe canceller (GSC) with a coefficient constrained adaptive blocking matrix and a filter based on minimum mean-square error (MMSE) criterion. It can reduce the leakage of the desired signal and enhance the capability of interference cancellation. The received signals of the main antennas and the reference antennas of the antenna array are input to the beamformer as desired signal and reference signal, respectively. Both simulated and experimental results show that the proposed beamformer can suppress the single-tone and phase modulation interference, whose frequency is close to the desired signal's frequency. The proposed beamformer has better effect and robustness on interference cancellation than the traditional GSC.

In order to effectively improve the communication quality in the extremely-low frequency (ELF) communication, a whole model of analog circuits and transform domain algorithm is constructed. Analog circuits include a pair of magnetic antennas, an amplifier and a group of filters. The distributed capacitance of the magnetic antenna is effectively reduced by the segmented winding method. Analog circuits used to amplify and filter received signal are designed. Besides, a magnetic sensor with high sensitivity is produced. The Karhunen Loève transform (KLT) algorithm applied to the field of interference suppression is deduced in detail. The transform successfully passes the received signal along the basis vector in sub-band, but the interference signal along the vector is attenuated. Therefore, the problem of the optimal filter converted into the solution of transform factor for each sub-band. Then the relationship between the KLT transform and the time domain algorithm in the interference suppression problem is given. Based on the KLT algorithm, Fourier transform (FT) that makes the correlation matrices of the received signal diagonalized approximately is applied to the interference suppression algorithm. Based on the deduction results, the final optimal filter expressions are basically the same as the KLT algorithm. Finally, the experiments are carried out by using the simulated signal and real collected data in the laboratory, respectively. The schematic diagram of the real collected device is presented. The experimental result shows that, no matter the analog signal or the real collected data, the proposed algorithm can effectively suppress the interference. For the simulation, the performance of KLT algorithm is basically same as that of FT algorithm, but KLT algorithm is obviously better than FT algorithm for real collected data.

In this paper, based on different saliency ratios ρ, three interior permanent magnet (IPM) synchronous machines respectively owning a large ρ, a low ρ and an inverse ρ are proposed for the potential applications of electrical vehicles (EVs). To grasp the impacts of saliency ratio on machine performances, comparative studies are conducted at low speed operation (constant torque region) and high speed operation (constant power region), respectively. In particular, the overload capability referring to magnet demagnetization is emphasized in low-speed heavy-duty operation region. And in high speed, the constant power speed range (CPSR) and high efficiency range are investigated. The main results put in evidence the different behaviors of the three machines in terms of EVs operating conditions. Though all three machines reveal considerable behaviors in CPSR, the inverse saliency ratio machine shows a larger high efficiency region and extends the high efficiency region to a wider speed-and-torque range due to its unique characteristic of L_q<Ld.

A novel and compact conformal printed dipole antenna with geometrical modifications in ground plane is proposed in this paper for 5G based vehicular communications and IoT applications. The proposed antenna consists of a printed dipole as defected ground structure and a staircase structured offset fed integrated balun to attain wideband operation. It yields a better -10 dB impedance bandwidth of 17.65 GHz and 2.24 GHz over the frequency ranges 24.3 to 41.95 GHz and 49.91 to 52.15 GHz. Antenna projects the peak gain of 6.81 dB with 98.82% of peak radiation efficiency. The measured results of the proposed model are in good agreement with the simulation obtained from HFSS. The conformal models of the proposed antenna are developed to embed the antenna in different curved surfaces on vehicular body. The analyzed conformal characteristics of the antenna support excellent constant reflection coefficient with respect to planar structure of the antenna over the operating band at different angles.

Effects of a superstrate layer on the resonant frequency and bandwidth of a high T_c superconducting (HTS) circular printed patch are investigated in this paper. For that, a rigorous full-wave spectral analysis of superconducting patch in multilayer configuration is described. In such an approach, the spectral dyadic Green's function which relates the tangential electric field and currents at various conductor planes should be determined. Integral equations are solved by a Galerkin's moment method procedure, and the complex resonance frequencies are studied with basis functions involving Chebyshev polynomials in conjunction with the complex resistive boundary condition. To include the superconductivity of the disc, its complex surface impedance is determined by using London's equation and the model of Gorter and Casimir. Numerical results are compared with experimental results of literature as well as with the most recent published calculations using different methods. A very good agreement is obtained. Finally, superstrate loading effects are presented and discussed showing interesting enhancement on the resonant characteristics of the superconducting antenna using combinations of Chebyshev polynomials as set of basis functions.