In this paper a novel design to reduce mutual coupling in circular patch antennas is proposed. A circular MIMO antenna with a dumb-bell shape parasitic element is inserted between the two circular patch antennas thereby reducing the mutual coupling. It has been observed that the proposed design produces a multi-band characteristics at 3.1 GHz, 6.2 GHz & 7.7 GHz. At the tri-band frequencies impedance bandwidths (IBW's) are around 90 MHz, 320 MHz, and 540 MHz. The process involves cutting rectangular slits on each side of a circular patch and placing a dumb-bell shaped parasitic structure to reduce the transmission coefficient (S₁₂) to -40.75 dB. It is observed that the antenna parameters are greatly improved in terms of ECC, diversity gain, directivity, group delay and peak gain which are 0.005, 9.973 dBi, 6.14 dBi, 10.81±1 nsec and 3.59 dBi. The results of experimental validation and numerical analysis are presented. The antenna design can be used for wireless communication as well as all C-band applications.

This paper presents a novel design methodology for the design and optimization of a miniaturized multiband microstrip patch antenna (MPA) suitable to be used in wireless communication systems. Two design steps were used to do that. In the first step, an initial antenna is designed by a trial and error approach to nearly operated in the desired frequency bands, but the level of impedance matching (S₁₁<-10 dB) for one or more bands is unsatisfactory, or some bands are uncovered by the antenna. Then, the second design step is beginning after that aiming to achieve optimized antenna by applying an optimization algorithm to effectively fine-tune the impedance matching of the initial deigned antenna to closely satisfy all the desired frequency bands. As an illustrative example, the proposed optimization methodology was used for designing a miniaturized multiband MPA suitable for operating at five different frequency bands, 915 MHz (RFID band), 1850 MHz (GSM band), (ISM-Industrial, Scientific, Medical), 2.45 and 5.8 GHz, and 3.5 GHz (WiMAX band). The proposed MPA used here is composed of two patch structures printed on both sides of an FR4 substrate occupying an overall size of just 28×28 mm². The final optimized antenna is fabricated, and its simulated and measured results were coinciding with each other validating the design principle. Moreover, simulation antenna performance parameters, surface current distribution, realized peak gain, and efficiency besides the radiation patterns at the desired frequency bands are obtained using CST MWS.

A miniaturized TM21 mode circular patch antenna is introduced. The miniaturization is realized by loading the patch with four symmetric radial slits, which facilitate elongating the current path and thus reducing the resonant frequency and the patch size. In particular, the eigenvalue of the proposed higher order mode is reduced to that of a conventional dominant TM11 mode antenna, resulting in about 40% reduction in the radius. The effects of the slit geometry on miniaturization and resonant frequency are studied. The measurement results are also presented, which are in good agreement with the simulation ones. Such miniaturized TM21 patch antennas with conical radiation patterns have manifold applications in phased array antennas for booming communication demands.

In order to solve the high harmonic content of permanent magnet synchronous motor (PMSM) for fitness car, a PMSM with built-in permanent magnet bridge is proposed in this paper. Compared with surface mounted permanent magnet synchronous motor (SM-PMSM), the proposed motor with permanent magnet bridge structure has lower harmonic content. The performance and magnetization angle of the proposed motor are compared and analyzed in detail. The results obtained from finite element analysis show that the permanent magnet bridge can increase the air gap magnetic field intensity, and different directions of magnetization will affect the amplitude of fundamental wave of air gap magnetic density. Moreover, it can reduce the total harmonic distortion (THD) and make the magnetic density waveform more sinusoidal. It is very beneficial to the smooth output of torque of fitness car.

The design guidelines have been proposed for achieving efficient wireless Electric Vehicle (EV) charging system under non-ideal practical scenarios. The effects of operating parameters have been investigated by addressing the fundamental hurdle to the widespread usage of magnetic resonance coupling (MRC) based wireless EV charging system. From both experimental and simulated results, it has been perceived that the power transfer efficiency (PTE) depreciates rapidly as the charging condition deviates from the ideal one. It is observed that PTE can be managed to enhance from the deteriorated value to an acceptable level through proper consideration of separation air gap of the charging coils, frequency of operation with acceptable horizontal offsets, suitable coil models, position of metallic object and coil properties. To maintain the maximum PTE even under non-ideal scenario, an automated frequency tuning method has also been delineated. The corroborated experimental and simulated results can provide a complete strategic plan in the design of an efficient practical wireless power transfer system to be utilized for EV charging system.

A compact wideband circularly polarized (CP) square slot antenna for universal ultra high frequency (UHF) RF identification (RFID) handheld reader applications is proposed, fabricated, and tested. The antenna is coplanar waveguide (CPW) fed by an inverted Z-shaped feeding line. By inserting four stubs in diagonal directions and two inverted T-shaped strips inside the square slot, broadband CP operation, wide axial ratio bandwidth, and good impedance matching are achieved. The measured < -10 dB impedance bandwidth is from 706 MHz to 1007 MHz (301 MHz, 35.1%). The measured 3-dB axial ratio (AR) is 427 MHz (745-1172 MHz, 44.5%). The maximum measured gain of the proposed antenna is 4.8 dBi. The proposed antenna has wide impedance bandwidth, wide axial ratio bandwidth, and small size. The dimensions of the antenna are only 120×120×1.6 mm³. The impedance bandwidth and AR bandwidth performances of the proposed antenna can easily cover the UHF RFID band as whole.

The paper presents a new method of dispersion compensation. It aims to reduce the dispersion effect of the wave throughout its propagation in the cable. The main objective is to improve the defects localization accuracy in electrical cables. This suggested method can be applied to any test signal injected in the line under test.

In this article, a microstrip-fed stepped open slot antenna is presented which is suitable for GSM 1800, WiFi, WiMAX, PCS, and ITM-2000 applications. The proposed geometry is composed of a circle-shaped tuning stub, a feed structure, and deformed ground plane. The proper tuning of resonating modes (f_r1, f_r2, f_r3 and f_r4) and wideband frequency response are acquired by adjusting the dimension of stairs, tuning the stub and an elliptical slot. The experimental result demonstrates that this antenna covers the frequency range from 1.375 to 5.6 GHz with measured fractional bandwidth (BW(%)=200 * (f_h - f_l)/(f_h + f_l) of 121.14% for S₁₁<-10 dB. This antenna also exhibits resonance at frequencies (measured) 1.625, 2.52, 2.82, 3.75, 4.67, and 5.42 GHz. After investigating the surface current distribution, the mathematical equations are deduced for simulated resonating frequencies of 1.35, 2, 3.8, and 5.22 GHz. Due to asymmetry in structure, asymmetric far-field patterns are found in E-plane with omnidirectional patterns in H-plane.

This paper proposes and implements a novel class of inductor-capacitor-capacitor wireless coordinative DC motor drives, which not only performs selective wireless power to motors, but also achieves power equalization to ensure the same operation for isolated robotic arms. The key is to make use of the selective wireless power transfer with several resonant frequencies and then use only one transmitter with the inductor-capacitor-capacitor compensation network to provide multiple-frequency transmission without relying on the switched-capacitor array. In order to provide simultaneous and independent wireless power to different motors and hence achieve the desired coordinative motion, a time-division multiplexing scheme and burst firing control are newly employed. Thus, the wireless power transfer system with multiple receivers can achieve better flexibility and simplicity. Both finite element analysis and experimental results are given to verify the validity of the proposed inductor-capacitor-capacitor wireless coordinative DC motor drive. As a result, the motors can achieve independent motion with 1200 rpm and simultaneous motion with 400 rpm when the torque is 10 Ncm, and the operating frequencies are set at 110 kHz and 130 kHz.

A compact dual-band substrate integrated waveguide (SIW) crossover with high isolation is proposed. Two identical slots are etched on the ground plane to achieve dual-band response and compact size. The passbands are generated below the cutoff frequency of the SIW due to the electric dipole behaviour of the slots. In-line ports are also employed to obtain good transmission and high isolation. To validate the concept, a dual-band crossover operating at 2.4 GHz and 5.4 GHz is designed, fabricated, and measured. The crossover size including in-line ports is 43.2×43.2 mm², equivalent to 0.43λ_g×0.43λ_g, here λ_g is the guided wavelength at the first operating frequency. The tested insertion loss and isolation at the two operating frequencies are smaller than 0.27 dB and greater than 40 dB, respectively.

This paper presents the realization of Nonstandard Finite Difference Time Domain (NS-FDTD) analysis having high accuracy and low computational cost to a negative permittivity metamaterial wire medium for the first time. A sine wave of frequency less than that of plasma frequency of the medium which is in the shape of a slab reflector is allowed to interact after identifying the exact values of the required stability condition of the NS-FDTD. The electric field distribution around the plasma slab obtained for a particular excitation point using NS-FDTD and standard FDTD are demonstrated which show obvious advantages of this high accuracy algorithm. This novel technique may be further extended to various dispersive and metamaterial structures.

The average downlink data-rate in massive Multiple Input Multiple Output (MIMO) networks within realistic urban environments is characterized by means of ray-tracing simulations. The links between the receivers and transmitters are mostly established through rooftop propagation, which requires special treatment due to multiple diffractions near the optical boundaries. The bidirectional ray-tracing method is utilized in order to simulate these effects accurately. The average downlink data-rate is also calculated according to an empirical rooftop propagation model and the differences as well as the similarities with the bidirectional ray-tracing results are demonstrated. Additionally, an iterative Shooting and Bouncing Rays (SBR) algorithm, which improves the computational efficiency of the bidirectional ray-tracing, is introduced. The algorithm aims to maximize the number of rays, which contribute to the result, by setting specific launch directions. The results show that noticeable improvements in the computation time are possible.

In this paper, a wideband polarization diversity multi-input multioutput (MIMO) antenna system is proposed. The structure of the proposed antenna consists of four wideband coplanar waveguide (CPW)-fed monopole antennas with a common ground plane and radiated element. The simulated and measured -10 dB impedance bandwidth is 20% (2.25-2.75 GHz), which covers WiFi (2.4 GHz) and LTE (2.6 GHz) frequency bands. The MIMO antenna system is applied to both an indoor and outdoor wireless access point (WAP) at the covered frequency bands. Due to the common structure of elements in the proposed MIMO antenna, an acceptable mutual coupling between the antennas ports is critical. Hence, a new parasitic element structure is presented to improve mutual coupling between the antenna ports. Acceptable values for the coupling coefficient (<-14 dB) are achieved by adding the parasitic element. The presented antenna system provides a nearly omnidirectional radiation pattern with an orthogonal mode of linear polarization. The results show a polarization diversity gain of 10 dB and an envelope correlation coefficient of less than 0.2. Moreover, each antenna port possesses peak gains of 5.33-6.97 dBi and efficiencies of 51.5-57%. A comparison between the simulation results and experimental measurements reveals good agreement between the two, confirming the validity of the proposed design.

In this paper, a new design approach is presented for achieving a miniaturized quad-band microstrip patch antenna (MPA) suitable to be used for 915-MHz (UHF band), 2.45- and 5.8-GHz (ISM band), and 3.5-GHz (WiMAX band). The proposed antenna is called modified square spiral antenna (MSSA) which is composed of a modified dual-arm square spiral patch strip structure and a tapered-ground plane with coplanar wave-guide (CPW)-fed configuration to feed this antenna, all printed on the top side of an FR4 substrate. The proposed antenna is designed through intermediate systematic design steps of antennas starting from a conventional strip-fed rectangular MPA and ending by achieving MSSA. A CST Microwave Studio (CST MWS) is used to model the designed antenna and simulation results, in terms of return loss (S₁₁), realized peak gain and efficiency, besides to radiation patterns, are obtained. To validate the design concept, the antenna structure is fabricated, and the simulated and measured S₁₁ results nearly coincid with each other. The proposed antenna is characterized by miniaturized size of 28×28 mm², and based on measured -10-dB S₁₁ result, MSSA has four bands, band 1: 915-GHz (872-929 MHz), band 2: 2.45-GHz (2395-2510 MHz), band 3: 3.5-GHz (3470-3550 MHz), and band 4: 5.8-GHz (5698-5900 MHz).

In this work, a simple propagation channel model for microwave-based pinless subsea connectors in the 5 GHz band is presented. Both high electromagnetic attenuation in seawater due to absorption and the near-field working conditions typically present for underwater connectors are taken into consideration. Therefore, a simplified path loss model based on linear regression is identified. The study shows that high-speed pinless subsea connectors are a reality over several cm of seawater gap when appropriate microwave receiver technology is selected with sensitivities of about -100 dBm. Experimental results show that both half-duplex gigabits-per-second and full-duplex 100-Mbps technologies have a strong potential to be developed in the 5 GHz band.

In this paper, a novel high-gain repeater antenna integrating a dual-feed network is proposed to receive and transmit RF signals separately by two ports. The proposed array antenna has four linearly polarized microstrip antenna elements, two feed networks, and one planar magic-T. The distance between the elements of the array antenna is matched to obtain the minimum sidelobe level and maximum half-power beamwidth for transmitting and receiving purpose. The planar magic-T is effectively used to meet two different bi-directional radiation patterns with a simple structure. Performances of the array antenna are experimentally confirmed, and the gain of the antenna for each port is better than 10.3 dBi. The measured 10-dB impedance bandwidth of the antenna is wider than 580 MHz (10%).

The context of the paper is the 50-60 Hz electromagnetic interference between AC power lines/electrified railway lines and pipelines; we present here an algorithm for the evaluation of the AC induced current density, flowing through the holidays (defects) in the pipeline insulating coating, from pipe to soil by modelling this last one as a two-layer structure. Moreover, the value of holidays area is treated as a random variable (as actually is from field experience) so allowing to associate a certain level of probability to the event of exceeding the AC current density limit, established by standards, for AC corrosion risk. The results show that the surface layer soil resistivity is a very significant factor influencing the level of AC induced current density.

In this paper, an electronically switchable ultra-wideband (UWB)/dual-band bandpass filter using defected ground structures (DGSs) is proposed. The proposed filter consists of meandered inter-digital coupled line sections, stepped impedance open stubs, coupled lines, and rectangular DGSs to realize high performance in the operation band with a compact size of 12.5 mm × 10 mm. The proposed filter is designed on an RT/Teflon substrate (ε_r = 2.2, h = 0.7874 mm). The main advantage of the proposed filter is the reconfiguration of ultra-wide bandpass filter to dual-band bandpass filter. UWB has passband from 3.6 GHz to 10.6 GHz with upper wide stopband attenuation better than 20 dB up to 18 GHz. The dual passbands extend from 3.8 GHz to 5 GHz and from 9.5 GHz to 10.8 GHz. This filter is able to provide interference immunity from unwanted radio signals, such as wireless local area networks (WLAN), worldwide interoperability for microwave access (WIMAX) that cohabit within the UWB spectrum, and X (Military) band of satellite from 7 GHz to 8 GHz. The state of filter can be changed by using switching matrix equipment (mini circuit, replacement of PIN diodes). To validate the design theory, an electronically switchable UWB/dual-band bandpass filter using DGSs is designed, fabricated, and measured. Good agreement is found between simulated and measured results.

Convolutional Neural Network (CNN) models applied to synthetic aperture radar automatic target recognition (SAR ATR) universally focus on two important issues: overfitting caused by lack of sufficient training data and independent variations like worse estimates of the aspect angle etc. To this end, we developed a lightweight CNN-based method named SARNet to accomplish the classification task. Firstly, a clock-wise data amplification approach is presented to generate adequate SAR images without requiring many raw SAR images, effectively avoiding overfitting in the course of training. Then a SARNet is devised to process the extracted features from SAR target images and work on classification tasks with parameters fine-tuning under comparative models. To enhance and structurally organize the representation of learned proposed model, various activation functions are explored in this paper. Furthermore, due to the pioneering conducted experiments, training samples in the MSTAR and extended MSTAR database are utilized to demonstrate the robustness and effectiveness of the lightweight model. Experimental results have shown that our proposed model has achieved a 98.30% state-of-the-art accuracy.

In this paper, an antenna composed of an inverted L-shaped feeding strip and a shorting strip with three branches for LTE/WWAN mobile phones is presented. With the help of novel ground plane slots, the proposed antenna can realize miniaturization (34×15 mm²) and multiband to cover LTE/WWAN bands. The measured bandwidth (3:1 VSWR) of the proposed antenna is 156 MHz (810-966 MHz) at the low band and 1937 MHz (1548-3485 MHz) at the high band. Moreover, the lowest measured radiation efficiency of the fabricated antenna is more than 54% in the whole operation band. The proposed antenna has been successfully fabricated and measured, and there is a good agreement between simulated and measured results.