A superconducting synchronous generator (SSG) is proposed for wind power, in which magnesium diboride (MgB₂) superconducting coils are employed as field windings. The stator is composed of conventional copper coils and iron core, while the rotor has no iron core. The whole refrigeration method is adopted in this paper. The thermal barrier is not placed in between the stator and the rotor as compared with the prior HTS generators, so a small air gap width would be possible. In order to study the electromagnetic characteristics of the SSG, finite element method (FEM) is implemented to optimize the SSG and obtain the no-load and load performance of the initial and optimized SSG. Finally, the optimized SSG is compared with a traditional synchronous generator (TSG) of the same power. The results indicate that the optimized SSG has many merits such as small size, light weight, high efficiency and high power factor.

In this part, we develop an efficient algorithm for the computation of the complete transmitted and reflected electromagnetic fields in generic 2D arrays of carbon nanotubes (CNTs). The method relies on first approaching individual CNTs using an effective-boundary condition based on a proper quantum conductivity model. An exact eigenmode solution is obtained for this problem for both single-wall and multi-wall CNTs, which then is integrated with Floquet mode theory to handle periodic arrays of CNTs. The algorithm's convergence rate is accelerated using special methods and then applied to the analysis and design of various multi-layered CNT-based photonic crystals. It is shown that the proposed method can clearly demarcate the intrinsic resonances due to electronic transitions in individual CNTS and new sets of geometric resonances produced by the array environment. The algorithm can be used to analyze measured optical spectra of CNT composites and to design new optical bandgap devices.

In this paper the equivalent impedance of resonator arrays for wireless power transfer systems is obtained in closed-form from a continued fraction expression. Using the theory of difference equations, the continued fraction is described as the general term of a complex sequence defined by recurrence, and its convergence is analyzed. It is shown that the equivalent impedance can be easily found in closed-form in terms of the system parameters. In this way, the obtained closed-form expressions may help electrical engineers to quickly predict the behaviour of a system with the changes of its parameters. Some numerical examples of the theoretical results are given and discussed. Finally, the analytical formulae obtained in this work are validated with measurements and a good agreement is observed.

Radio wave energy harvesting has become one of the most fascinating fields of research, especially in developing antenna for its front end subsystem. This paper presents the development of a single large aperture antenna for energy harvesting system. Three substrate layers FR4-air-FR4 are employed to increase the antenna gain. Measurement result shows that the proposed antenna is able to obtain gain of about 9.61 dBi at 1.575 GHz (GPS L1 frequency), with low return loss of about -17.12 dB. The achieved bandwidth is about 128 MHz. The antenna characteristic is suitable for energy harvesting application.

A highly miniaturized significant gain triple band patch antenna loaded with a new modified double circular slot ring resonator (MDCsRR) metamaterial unit cell is presented in this paper. Novel MDCsRR is a compact low frequency slot ring resonator. The principle of the proposed patch antenna element is based on adding series capacitance to decrease the half wavelength resonance frequency, thus reducing the electrical size of the proposed patch antenna. The transmission line model is used to analyze passband and stopband characteristics of the radiating bands. Circulating current distribution around MDCsRR slot with increased interdigital capacitor finger length causes multiple modes to propagate. The MDCsRR metamaterial unit cell consists of a new modified circular slot ring resonator (MCsRR) with metallic strip finger. The proposed structure is compact in size with radiating element dimensions of 0.20λ × 0.20λ × 0.008λ at first resonating frequency. The proposed antenna offers triple band operation with significant calculated antenna gain of 3.28 dBi at first center frequency of 3.2 GHz, 2.76 dBi at second center frequency of 5.4 GHz and 3.1 dBi at third center frequency of 5.8 GHz. The electrical size of the proposed antenna is miniaturized by about 68.83% as compared to the conventional patch antenna operating at first resonating frequency.

With the increase of low power devices, the design of a compact and efficient rectenna is essential for supplying energy to the devices. This paper presents a compact rectenna for high efficient WiFi energy harvesting. A novel fractal geometry is introduced in the design of antenna for miniaturization, and the ability to harvest WiFi energy is enhanced due to its characteristics of self-similarity and space filling. Besides, a single stub matching network is designed to achieve high conversion efficiency with a relatively low input power ranging from -20 dBm to 0 dBm. Simulation and experiments have been carried out. The results show that the proposed antenna features a good characteristic of reflection coefficient and realized gain at WiFi band. The highest RF to DC conversion efficiency of the rectenna is up to 52% at 2.48 GHz with the input power of 0 dBm. This study demonstrates that the proposed rectenna can be applied to a range of low power electronic applications.

A quasi-millimeter electromagnetic wave with the frequency of 22-30 GHz is applied to detect knots and holes in wood samples. It has better spatial resolution while keeping good transmission properties compared to microwave region used in the previous experiments. The images of knots and holes in wood are clearly obtained by analyzing the phase and amplitude of the transmitted wave. And the phase measurement results are all better than amplitude results according to phase values changing much more than amplitude.

A very simple design method to embed routing capabilities in classical corrugated filters is presented in this paper. The method is based on the calculation of the heights and lengths of the so-called filters design building blocks, by means of a consecutive and separate extraction of their local reflection coefficients along the device. The proposed technique is proved with a 17th-order Zolotarev-filter whose topology is bent twice so that the input and output ports are in the same plane while preserving the in-line filters behaviour. This new filter allows the possibility of eliminating subsequent bending structures, reducing the insertion loss, weight, and PIM.

The surface plasmon effect in metallic photonic crystals has been investigated. Band structure graph is the only graph that can be used to explain the characteristics of photonic crystals. In this work, band structure graphs have been used to describe these characteristics, which include the surface plasmon effect of photonic crystals. Recently, band structure graphs for frequency-dependent materials have been analyzed by several researchers. The surface plasmon effect has been found for these materials. This article reports the effect of surface plasmons which cause resonance state in the metallic photonic crystals when the relative permittivity is changed from band structure graphs. The numerical results from the commercial software show the magnetic field distribution of waves on the normal photonic crystals, and defect mode is added for each frequency.

This article proposes a beam focusing compact wideband microstrip antenna loaded with mu negative (MNG) metamaterial. The antenna is designed to operate in the frequency spectra of IEEE 802.11a wireless LAN 5.15-5.85 GHz. The controlling of the beam direction has been investigated using eight different switching combinations of 12 PIN diodes which are integrated in the metamaterial unit cells. The main beam is found to be focused in -ve y, +ve y and omnidirectional in yz plane in agreement with switching condition of the metamaterial unit cell. The maximum gain enhancement of 7 dB is obtained at 4.9 GHz as the beam of the power pattern is focused in the negative y direction. The basic antenna with patch dimension (0.14λ × 0.14λ) provides wide impedance bandwidth of about 40%. Two prototypes of basic and proposed antennas have been developed using a low profile FR-4 substrate. The simulation results are found in good agreement with the measurement ones.

A novel miniature microstrip-fed multiband antenna for wireless local area network (WLAN) and X-band satellite communication applications is presented in this paper. The proposed antenna consists of two arc-shaped strips, dual inverted L-shaped parasitic stubs and a partial ground plane. The proposed antenna can excite multi-resonant modes while achieving a compact size of 18×34.5×0.8 mm³. The measurement results show that -10 dB impedance bandwidths are 290 MHz (2.28-2.57 GHz), 1.27 GHz (5.0-6.27 GHz), and 850 MHz (7.11-7.96 GHz), which can cover the entire operation frequencies of WLAN (2.48-2.4835 GHz, 5.15-5.875 GHz) and X-band satellite communication system (7.25-7.75 GHz) applications.

In this paper, a new microstrip balanced-to-balanced diplexer is presented and investigated. The proposed diplexer primarily consists of two balanced bandpass filter paths, and each balanced filter path can be designed independently based on two identical stub-loaded triple-mode resonators. It should be mentioned that no extra matching networks are required at the common balanced input port in the design. For demonstration, a prototype balanced-to-balanced diplexer operating at 2.30 and 2.83 GHz is designed, fabricated and measured with 3-dB fractional bandwidths of 13.0% and 13.4%. Both simulated and measured results are provided in satisfactory agreement.

Processing over-the-horizon radar (OTHR) signals is challenging due to appearance of several very close components in the time-frequency plane, strong noise and clutter, multipath propagation, and aliasing. We propose a two-stage procedure for estimating multipath signal components from the received mixture. In the first stage, the instantaneous frequency is estimated from the time-frequency representation of the received signal. The random samples consensus algorithm is applied to the instantaneous frequency estimate to improve the robustness of the procedure against various effects in the underlying signals. In the second stage, the MUSIC algorithm is applied to the dechirped and downsampled signal. The effectiveness of the proposed approach is verified using real-life signals.

A microwave diplexer implemented by using the twenty-first century substrate integrated waveguide (SIW) transmission line technology is presented. No separate junction (be it resonant or non-resonant) was used in achieving the diplexer, as the use of an external junction for energy distribution in a diplexer normally increases design complexity and leads to a bulky device. The design also featured a novel input/output coupling technique at the transmit and receive sides of the diplexer. The proposed SIW diplexer has been simulated using the full-wave finite element method (FEM), Keysight electromagnetic professional (EMPro) 3D simulator. The design has also been validated experimentally and results presented. Simulated and measured results show good agreement. The measured minimum insertion losses achieved on transmit and receive channels of the diplexer are 2.86 dB and 2.91 dB, respectively. The measured band isolation between the two channels is better than 50 dB.

A novel compact CPW (coplanar waveguide-fed) CPSS (Circularly polarized square slot) antenna is presented. The proposed single-layer antenna is composed of a rectangular ground plane embedded with two equal-size patches along two orthogonal directions. Equal amplitudes with 90˚ phase difference values of two patches is capable are generating a resonant mode for exciting two orthogonal E vectors. Axial ratio (AR) bandwidth is significantly enhanced due to slot corner modification. The designed CPSS antenna is compact in nature with volume of 0.37λ₀× 0.34λ₀ × 0.012λ₀ mm³ (λ₀= free space wavelength at centre frequency of the CP bandwidth). It has impedance bandwidth between 4.65-6.72 GHz (36.41%) and 3-dB axial-ratio bandwidth of 520 MHz (4.85-5.37 GHz), which covers 4.9 GHz (802.11j) WLAN for public safety ranging from 4.94 GHz to 4.99 GHz and WLAN (U-NII-1 and U-NII-2A) ranging from 5.150-5.350 GHz for indoor use. The gain variation for the frequencies within the CP bandwidth is also observed to be less than 0.6 dBic. The design is successfully implemented, and measured results are compared with the simulated ones, which are found in good agreement.

To improve HF detection of small RFID tags, a Distributed Diameter Coil (DDC) resonator is included in the reader coil. The key ideas of detection improvement are twofold: using a resonator with Magnetic Resonant Coupling (MRC) and modifying the distribution of diameter and current for each loop of the DDC resonator. These factors allow the magnetic coupling to increase between the reader and the smaller tag, especially in our case where the effective area of the tag is below 0,1% of the reader coil surface. Numerical simulations are carried out using HFSS to confirm the enhancement of the mutual coupling between the tag and the reader coil: the coupling coefficient is used in double-loop coupling (the case of the coupling of two loops), when a third loop (resonator) is inserted. The optimization of the magnetic coupling between a large reader and a small tag with resonator could be realized in changing first the sub-coil diameters, and then the sub-coil number of turns. One figure of merit to quantify the ability of surface detection is defined. A 15% improvement of detection surface in Horizontal Mode is measured at 1 cm of the reader plane in comparison with a conventional coil. Experimental detection measurements on real structures are described to validate statements.

A printed multiband multiple input multiple output (MIMO) antenna system is proposed in this paper. The MIMO antenna system is composed of two identical antenna elements which are perpendicular to each other. The defected ground plane with two microstrip lines is introduced to suppress the coupling between the antenna elements. The proposed MIMO system operates at two separated impedance bandwidths of 770 MHz (2.09-2.86 GHz) and 890 MHz (5.05-5.94 GHz) with an overall size of 50 × 50 × 1.59 mm³. The achieved isolation at the lower and higher frequency bands is higher than 20.9 dB and 17.8 dB, respectively. The proposed MIMO antenna system is feasible to be used for time-division long-term-evolution (TD-LTE, 2300-2655 MHz) and wireless local area network 802.11 a/b/g (WLAN, 2.4-2.4835 GHz, 5.15-5.875 GHz) applications.

The paper focuses on design and analysis of hexagon inspired fractal geometry and defected ground plane to evaluate the performance of patch antenna for wireless applications. It also emphasizes increasing the antenna bandwidth by incorporating novel rectangular Defected Ground Surface (DGS) structure with CPW feed. In the proposed work, antenna is simulated and fabricated for wireless applications using FR4 as the substrate, and it covers wide band with high gain. The antenna resonates at frequencies of 3.79 GHz and 5.5 GHz with measured return losses of -25.02 dB and -26.03 dB, respectively, making the proposed antenna suitable for Wi-Fi, cordless phone, wireless devices and wireless sensor networks applications.

A triply primed array (TPA) is configured on three mutually primed integers (N₁, N₂ and N₃), which operates with O(N₁N₂N₃) degree-of-freedoms to estimate the direction-of-arrivals (DOAs) of multiple incident quasi-stationary signals. The set of unique and contiguous lags of the proposed TPA is searched and verified. Simulation results verify that the proposed TPA can detect more incident signals with higher accuracy than its compatible counterparts.

This paper presents an efficient hybrid method consisting of finite-difference time-domain (FDTD) method, transmission line (TL) equations, and a fast calculation method for excitation fields, which can be applied to the coupling analysis of the shielded cable on the ground excited by plane wave rapidly. It can avoid modeling the infinite ground and the structure of the shielded cable directly. In this hybrid method, the shielded cable is decomposed into external and internal transmission line models, and the corresponding TL equations for the external and internal TL models are established necessarily. Then the FDTD method is utilized to solve the TL equations to obtain the transient responses on the shielding layer and core wires of the cable. A numerous examination of the coupling of coaxial cable exhibits that this hybrid method has very high accuracy and efficiency compared with the SPICE method. Finally, the methods of effective shielding protection of the cable have been proposed by analyzing the influences of the grounding states of the shielding layer, the electromagnetic parameters of the ground and the heights of the cable on the transient responses of the cable.