In this paper, a new measurement method is proposed to estimate the complex permittivity for each layer in a bi-layer dielectric material using a Ku-band rectangular waveguide WR62. The S_ij-parameters at the reference planes in the rectangular waveguide loaded by a bi-layer material sample are measured as a function of frequency using the E8634A Network Analyzer. Also, by applying the transmission lines theory, the expressions for these parameters as a function of complex permittivity of each layer are calculated. The Nelder-Mead algorithm is then used to estimate the complex permittivity of each layer by matching the measured and calculated the S_ij-parameters. This method has been validated by estimating, at the Ku-band, the complex permittivity of each layer of three bi-layer dielectric materials. A comparison of estimated values of the complex permittivity obtained from bi-layer measurements and mono-layer measurements is presented.

Efficiency of high frequency surface wave radars may be improved by inserting a metamaterial in the vicinity of transmitting antennas that will reinforce the propagation of surface waves. This paper deals with the first and second order derivations of the surface impedance boundary conditions (IBC) applied to model such a metamaterial, which is equivalent to a bounded ground with a low negative permittivity. The goal of this paper is to extend an approach previously based on the classical Leontovich IBC which is usually restrained to high permittivity grounds. As shown here, a simplification in the expression of the surface impedance is possible in the case of a planar and homogeneous surface. That allows to have a first order impedance boundary condition substituted for the required second order impedance boundary condition.

This paper presents the design and fabrication of an antenna based on Substrate Integrated Waveguide (SIW) for intersatellite crosslinks in C-band. The entire antenna consists of two elements of SIW slots array that is fed by a hybrid 3 dB directional coupler. The entire SIW slot array antenna is circularly polarized (CP), and each element has four longitudinal slots. The element's effective field matching is realized with a microstrip to SIW transition. The antenna design has been evaluated with its return loss, gain plot, and radiation pattern characteristics to validate the fabricated antenna. The fabricated prototype antenna radiates a left-handed circularly polarized (LHCP) electromagnetic wave with the peak gain of 5 dB and offers approximately 2% AR bandwidth around 5 GHz.

Radial flux Dual Stator Dual Rotor Permanent Magnet (DSDRPM) machine can be considered as an exterior rotor PM machine kept over an interior rotor PM machine. This facilitates with a scope for optimization of the relative placement of inner and outer stator slots of the machines to achieve cogging torque minimization. This paper deals with the analytical prediction of flux density distribution in an internal and external rotor PM machines with semi-closed slots and further utilizes it to calculate the cogging torque in DSDRPM machine. An optimal angle of shift between the stator slots of the two machines has been determined to obtain a reduction in the resultant cogging torque of DSDRPM machine. The analytical results are verified with the Finite Element Analysis (FEA) results and found to be in close agreement with each other.

In this paper a compact antipodal Vivaldi antenna with dimensions of 40×85 mm² for Ka band is presented. To enhance the antenna gain, epsilon near zero metamaterial (ENZ) unit cells are embedded at the same plane of the Vivaldi flare aperture. These ENZ unit cells have the advantage of confining the radiated fields with additional compact size. The obtained antenna exhibits an ultra-wide bandwidth from 23 GHz to 40 GHz with a reflection coefficient less than -10 dB. This is suitable for 5G applications at both 28 and 38 GHz. The antenna gain in this frequency band is found in the range from 14 to 17.2 dBi. The proposed antenna is designed by using CST-MW Studio, and the results are verified with experimental measurements.

For the first time, the concept of combinational use of subwavelength metasurfaces and plasma media is introduced in this paper for being utilized in practical radio frequency (RF) shielding applications. Using an equivalent circuit model, it is demonstrated that the simultaneous use of the lossy characteristic and special dispersion of plasma in low-frequency regime and the transmission zeros provided by spatially homogeneous metasurfaces in the upper frequency band results in superior shielding performances. The designed coating layer has an ultra-thin profile while exhibiting a super wide reject band ranging from 1 to 20 GHz (|S₂₁|<-10 dB). A fair comparison is also performed to elucidate that the proposed plasma-metasurface composite (PMC) shield outperforms the previously reported RF shielding FSSs in both bandwidth and thickness. The numerical results show that while maintaining a low profile, the shielding bandwidth of the designed PMC can be set to surprisingly include all the UHF, L, S, C, X, Ku, and K bands. Moreover, the designed coating layer provides a stable and polarization-insensitive reject band for different incident wave angles up to 45°. These superior performances, as well as the shielding tunability enabled by plasma, confirm the promising capabilities of PMC structures for various applications.

In order to have the required accuracies in method of moments (MoM) for numerical simulations of ocean scattering at microwave frequencies, we need to account for the much larger wavenumber of sea water relative to that of air. This paper presents simulation results of 2D ocean surface scattering with the required accuracies and that energy conservation is obeyed to 0.01%. A dense grid is required to discretize the MoM dual surface integral equation with up to 240 surface unknowns (120 surface electric field unknowns and 120 surface magnetic field unknowns) per free space wavelength. To solve the matrix equation efficiently, we develop a neighborhood impedance boundary condition (NIBC) technique to solve the matrix equation. We next calculate the emissivities of ocean surfaces using NIBC on surface integral equations using pulse basis/point matching and the Nystrom method. Results are illustrated for L-band and show that emissivities using NIBC combined with Nystrom are accurate to 2×10^-4 for vertical polarization and 10^-4 for the horizontal polarization. This means that our method can meet the accuracy goal of 0.2 psu salinity retrieval for the NASA Aquarius mission. Results of surface fields and emissivities are also compared to that of impedance boundary condition (IBC) which requires only 10 unknowns per free space wavelength.

GPS is well recognized as the best procedure for outdoor localization. However, it presents limits in indoor localization due to particular geometric difficulties that necessitate specific solution to locate a target inside a building. Also, radio frequency technologies have many disadvantages in indoor localization. Bluetooth and Radio frequency Identification (RFID) are unsuitable for real-time localization because of latency. Ultra-wideband (UWB) localization needs an expensive hardware. Zigbee presents a high interference with wide range of signal frequency because it operates in unlicensed Industrial, Scientific and Medical ISM bands. Light waves also present some limitations due to interferencesfrom fluorescent light and sunlight. The IR based indoor system has expensive system hardware and maintenance cost. To overcome limits and non-availability of radio waves and light waves, an acoustic solution using an array of microphones is presented as a solution for indoor localization, and an optimized deployment is used to improve precision and restrain error. The aim of this work is to propose a 3D indoor audio localization approach inspired by the principle of functioning of the human ear. In order to achieve our goal, we will use a genetic algorithm to obtain the optimized deployment of the used hardware.

In this paper, we deal with a frequency modulated continuous wave (FMCW) radar used for localizing and tracking targets by frequency evaluation of the received radar beat signal. The radar system achieved with a primary radar (reader) and a secondary radar (transponder) is addressed as super high frequency (SHF) radio frequency identification (RFID). Consequently, considering the transponder as an active target, we achieve an identification application thanks to the shift frequency induced by the transponder. Moreover, the impact of the non-linearity behavior of this transponder on the localization performance is investigated, and a solution is proposed for cancelling non-linear effects.

In this paper, a new formulation is proposed to solve an inverse scattering problem for locating isolated inclusions within a homogeneous noise-free and noisy biaxial anisotropic permeable background using MUltiple SIgnal Classication (MUSIC) algorithm. Locations of the dielectric, permeable, lossless and lossy electromagnetic or both dielectric and permeable inclusions with arbitrary ellipsoidal shapes in a noise-free or noisy background can be restored. The numerical study of different inclusions is illustrated, and accuracy of the method is investigated. The proposed formulation is also investigated for extended inclusions in both noise-free and noisy backgrounds.

To improve the power transfer efficiency in a magnetically-coupled resonant wireless power transfer (MCR-WPT) system, an efficient particle swarm optimization (PSO) algorithm based on the change of particle swarm scale is proposed. The transfer efficiency and frequency are used as the fitness function and particle position, respectively. Therefore, the optimal frequency can be obtained by adjusting the position of particle. Five types of optimizing process are presented and compared with the traditional PSO algorithm. It is found that the proposed method has faster convergence speed than the traditional PSO algorithm. Additionally, the proposed five types of optimizing process with different regulation parameters are investigated. The results indicate that Type 2 with n=3 is the best alternative in finding the optimal frequency with the fastest speed of convergence. Experimental prototypes have been set up for validation.

This paper presents the design of a compact-integrated reconfigurable rectenna array containing 2x2 compact microstrip patch antennas based on a fractal model with the rectifier circuit integrated into the same physical structure and usable in practical conditions. In this array configuration, four rectennas were mounted in a planar structure with total dimensions of 85x85 mm using FR-4 dielectric and with recongurable DC output that was tested in three ways: series-association, parallel-association and series-parallel association. In the series-association the rectenna array was able to generate the DC power that reached 6.51 V and maximum efficiency of 64.5%; in the parallel-association it generated the DC power that reached 1.58 V and maximum efficiency of 65.3%; in series-parallel-association it generated the DC power that reached 3.00 V and maximum efficiency of 64.5%. The results showed that rectennas in array configuration are feasible to be used as power supplies to electronic devices in real situations.

A size-reduced quarter-mode substrate integrated waveguide (QMSIW) band-pass filter (BPF) loaded with combination of complementary split ring resonator (CSRR) and capacitive metal patches is presented. The CSRR generates a passband below the characteristic cutoff frequency of the substrate integrated waveguide (SIW) cavity. Improved stopband rejection is also attainable by loading a capacitive metal patch. Thus, a single-layer compact BPF with wide stopband is realized successfully. The equivalent-circuit model has been derived and analyzed. To verify the validity of the presented method, an experimental filter centered at 2.45 GHz is fabricated and measured. The new filter has the return loss of 16 dB and insertion loss less than 0.9 dB. Out-of-band suppression is better than 20 dB from 3 GHz to 11.6 GHz. The whole size of the filter is only 20×17.4×0.508 mm³, achieving 75% size reduction compared to the conventional structure.

A wideband right-hand circularly polarized (RHCP) crossed-dipole antenna with wide impedance bandwidth (IBW) and axial ratio bandwidth (ARBW) is proposed in this paper. A pair of dipoles with modified arms and a novel back-cavity are introduced to enhance both the IBW and ARBW of a conventional crossed-dipole antenna. Simulated and measured results indicate that the proposed structure can improve the circularly polarized (CP) characteristics significantly. The IBW (|S₁₁|<-10 dB) and ARBW (AR<3 dB) are 100% and 89.1%, respectively. The total size is 0.4λ×0.4λ×0.15λ (λ being the corresponding free-space wavelength at the frequency of 2.2 GHz). With both the excellent CP operating bandwidth and compact size, the proposed antenna is attractive for broadband wireless communication systems.

This paper proposes a secure beamforming (BF) scheme for a dual-hop satellite communication system, where a satellite acts as a relay using amplify-and-forward (AF) protocol to assists signal transmission between the terrestrial source and destination, where the target user is intercepted by an eavesdropper (Eve) in the downlink transmission. By assuming that the satellite is deployed with multiple antenna feeds, we rst establish an optimization problem to minimize the on-board transmit power subject to the quality-of-service (QoS) and secrecy performance requirement of the destination. Then, based on the method of penalty function, we propose a secure BF scheme to obtain the optimal BF weight vector with analytical form. Finally, computer simulation results are given to demonstrate the eectiveness and superiority of the proposed algorithm.

This paper proposes the design of wide bandpass filters for Ku and Ku/K band applications. It has wide passband with miniaturization of size using folded substrate integrated waveguide (FSIW) technique. The filter is designed by introducing a C slot and an E slot in central metallic septum of FSIW respectively. The proposed filters are fabricated and tested after optimization. The fabricated E slot filter achieved enhancement in bandwidth with dual band operating in Ku band (14.35 GHz-16.76 GHz) and K band (18.66 GHz-19.61 GHz), respectively. The measured results match quite closely with simulated ones.

Cancer treatment is one of the several new applications which use subnanosecond pulse and picosecond high voltage pulse. In particular, picosecond pulses can introduce important non-thermal changes in cell biology, especially the permeabilization of the cell membrane. The Prolate Spheroidal Impulse Radiating Antenna (PSIRA) is used to radiate very fast pulses in a narrow beam width with low dispersion and high field amplitude. The beamwidth of the radiated pulse is further reduced by using near field focusing lens. In this proposed work, the compact partition lens system is designed for miniaturized PSIRA to focus the radiated impulse to the target (skin) location. The near field focusing lens is used to enhance the resolution on the target location. The PSR with Modified Bicone Antenna (MBA) with lens configuration provides greatly reduced spot size. The spot size on the target(skin) is measured as 3mm along the lateral direction and 6 mm along axial direction.

This letter presents a broadband circularly polarized (CP) crossed dipole antenna with wide axial ratio (AR) beamwidth. The antenna consists of a crossed dipole fed by two baluns, a wideband feed network and a cylindrical metallic cavity. To broaden the beamwidth, circular arms are introduced. Meanwhile, the metallic cavity is utilized to broaden the AR beamwidth. Measurements show that the antenna has an impedance bandwidth of 70.6% (1.87-3.91 GHz) for voltage standing wave ratio (VSWR) ≤ 2 and a 3-dB AR bandwidth of 62.4% (1.92-3.66 GHz). In addition, the 3-dB AR beamwidth of the antenna is larger than 100°, and the gain varies from 4 dBic to 6 dBic over the whole CP operation bandwidth. Owing to the high-gain and wideband operation, the proposed CP antenna is potentially capable for satellite applications and high-gain applications.

The interferometric synthetic aperture microwave imager (IMI) on WCOM is a onedimensional L/S/C tri-frequency microwave radiometer aiming to improve the measurement capability on soil moisture and ocean salinity. An IMI antenna system mainly consists of a parabolic cylinder reflector and a tri-frequency linear patch feed array. At present, an L-band ground prototype with a solid reflector and an 8-element feeds array is completed, with the imaging feasibility being verified by experimental results. In order to improve radiometer performance, this paper presents an improved antenna system, which is dedicated to the next generation of interferometric microwave imager prototype. Improvements made for the antenna system mainly include using deployable mesh reflector and increasing feeds. Simulation results of image reconstruction in viewing a series of near real case ocean brightness temperature maps are used to quantitatively compare and analyze imaging performances of the two L-band IMI prototype antenna systems.

In this paper, a novel miniaturized circularly polarized (CP) antenna is proposed for use in B3 band of Compass Navigation Satellite System (CNSS). The primary radiator is a hexagon patch with four bending strips. A shorting pin is loaded with each strip to miniaturize the dimension of the proposed antenna, which achieves a small electrical size of 0.11λ×0.11λ×0.068λ (λ being the wave-length in free space at 1.268 GHz). In order to improve the bandwidth, Y-shaped coupled patches and bending-strips, which act as reactive loading are coupled to an octagon patch. Four coupled bending-stubs with same turning directions of bending-strips, are sequentially placed at the edge of the octagon patch to enhance CP performance. Finally, a prototype of the antenna is implemented and measured. The experimental results reveal that the proposed antenna achieves impedance bandwidth (IBW) of 19.6% (1.175-1.430 GHz) for |S₁₁|≤-10 dB and 3-dB axial-ratio bandwidths (ARBW) of 27.5% (1.000-1.320 GHz). The radiation efficiency is more than 75%, and the gain keeps above 1.98 dBic over the B3 band. Thus, the proposed antenna can be a good candidate for the applications of CNSS.