This paper presents the theoretical basis and experimental validation for a technique to remotely characterize materials using FMCW radar sensors with complex baseband architecture. Our theoretical work proves that the magnitude and phase of the input reflection coefficient of a material can be accurately extracted from the baseband data of a complex-baseband FMCW radar. This complex reflection coefficient can be used to calculate the dielectric constant, loss tangent, thickness, and layer setup of a material with high accuracy due to the extra information obtained from the phase of the reflection coefficient. The analysis starts with a theoretical model for the complex reflection coefficient of a flat material slab suspended in air. We then introduce a formulation for the complex reflection coefficient existing in the complex baseband of an FMCW radar signal. We finally present the experimental testing preformed using TI mmWave radar on two different material samples and introduce the test results for extracting the material dielectric properties and thickness using three different extraction methods compared against nominal values from literature. The test results prove the high accuracy of our technique resulting from the utilization of both magnitude and phase information of the input refection coefficient, despite the relatively long free-space measurement distance and the multi-path reflections test environment.

This paper presents a 3 dB compact Ultra-Wide-Band (UWB) Substrate Integrated Gap Waveguide (SIGW) based hybrid coupler suitable for 5G mm-wave applications. It is a key component in signal processing for wireless communication. It provides a way to control the power distribution of the signal along different ports. It could be used to achieve beamforming and adaptive antenna system. The design steps started with implementing a unit cell of the gap waveguide structure satisfying the required bandwidth of the coupler. A supercell is then implemented. A network of complete ridges is constructed. A further step is to design a coupling section which achieves the required power distribution along the coupling and isolated ports. This coupling section is implemented using a novel approach of inserting an elliptical slot with variable major and minor axes with a certain orientation that achieves the standard performance of a 3 dB directional coupler with 90° ± 5% phase shift. For precise adjustment of this amplitude and phase, vias are further added perpendicular to the major axis of the slot. Its dimension and location have to be optimized. The Finite-Integral-Time-Domain (FDTD) analysis method is adopted (CST Microwave Studio). In addition, another novel approach is developed on this coupler such that the transition and gap layer is implemented on the same PCB layer, which saves the number of layers to only two layers compared to the usual three layers used in literature. Also, using SIGW technology saves the collapse of the top ground layer on the ridge structure, and only plastic pins are used to fix the two layers. The proposed coupler is fabricated and tested, and the results show that it serves the majority of frequency bands employed in 5G systems in the USA and Canada.

The response of a uniformly moving metallic slab to an electromagnetic plane wave, at normal incidence, is studied. The analysis is based on the application of boundary conditions to Maxwell's equations as a function of time. The Doppler effect and amplitude of the obtained reflected wave agree with the literature. Moreover, a transferred wave which has not been analyzed in the literature is demonstrated. The frequency shift and the amplitude of this wave are studied analytically with the same technique used for the reflected wave. The transfer of electromagnetic wave through the metallic slab is made possible by the presence of a static magnetic field inside the moving metallic slab, if the motion of the slab is opposite to the direction of propagation of the incident wave. The amplitude of the transferred wave is approximately 2v/c times the amplitude of the incidence wave, with v being the speed of motion and c the speed of light in vacuum. This amplitude is thus very small for non-relativistic speeds. The analytical results are validated by full-wave simulations based on the Finite Difference Time Domain method, where both reflected and transferred waves are demonstrated. Furthermore, numerical electric field and magnetic field distributions are presented at different time instants.

A low cost and compact chipless Radio Frequency Identification (RFID) humidity sensor with the size of 18 * 18 * 0.5 mm³ is designed for environmental humidity monitor. The sensor consists of a circular resonator and a rectangular substrate, which utilizes the polyvinyl alcohol (PVA) humidity sensitive material for relative humidity (RH) sensing. The PVA humidity sensitive material covers the sensor surface. The working principle of the sensor is that the change of environmental humidity results in the changing of dielectric constant of PVA and thus shifting of the resonant frequency of the sensor. The real-time humidity can be observed by monitoring the resonant frequency. The simulation results show that the humidity sensing range of the designed humidity sensor is 21.9% RH~52.5% RH, corresponding to the resonant frequency range of the sensor from 2.76 GHz to 2.51 GHz with the total offset 250 MHz. The maximum humidity sensitivity was 23.08 MHz/% RH within the monitoring range. The designed humidity sensor has the advantages of low cost, compact and simple structure, which is suitable for humidity monitoring in various complex environments.

This paper presents a novel dual-band dielectric electromagnetic band gap (EBG) antenna that operates in both wireless local area network (WLAN) and X-band satellite applications. The proposed structure comprises new double EBG layers placed on the top face and fed by a coaxial probe. The design and parametric analysis of the band gap structure have been performed using Ansys HFSS simulation software. The measurement results are found in good agreement with the simulation results, indicating that the proposed antenna design is a promising solution for dual-band applications. As a result, we have found significant enhancement in gain up to 8.1 dB and 9.3 dB at both frequencies of 5 GHz and 9.8 GHz.

An efficient method for designing narrow beams having minimum peak side lobe level (PSLL) and maintaining power efficiency (reducing active elements) for 5G/6G base stations with large antenna arrays is proposed. To ensure high efficiency in a multi-dimensional complex nonlinear optimization problem with several constraints thinning of antenna of antenna arrays is considered. For performing exhaustive search on the large number of feasible solutions a novel algorithm named discrete cat swarm optimization (DCSO) is usedand is a binary adaptation of real-valued cat swarm optimization (CSO). To testify the efficiency of DCSO a set of standard benchmarked multimodal functions are used. The proposed algorithmsexhibit heuristic nature, so the stability of the proposed method has been authenticated by using statistical test. Later the algorithm is applied to the optimization of a large planar antenna array (PAA) of size 10×20 (200 elements) to suppress the PSLL. Furthermore, the results of the synthesis are compared with literature marking low PSLL and convergence speed as pointers. The comparative results delineate the superiority of the DCSO over the existing discrete versioned traditional algorithms with respect to solution accuracy and speed of convergence. DCSO introducesa higher degree of flexibility to the field of binary-valued thinned antenna array synthesis problems.

In this paper, a new design of a highly isolated tri-band antenna for 5G and future 6G applications is proposed. The overall dimensions of the proposed antenna are just 56.4 × 36.6 mm²; moreover, it contains two monopole antenna units and a defective ground. The tri-band characteristics of the antenna are achieved by improving the single antenna patch structure. The structure is improved based on the original T-shaped decoupling structure to create a fence-shaped decoupling structure consisting of an improved T-shaped and an improved rectangular structure. This will greatly improve isolation by efficiently absorbing the coupling current. Therefore, the proposed antenna system is designed and tested to reach the 5G dual bands of 3.38 GHz-3.61 GHz, 4.51 GHz-4.96 GHz, and the future 6G band of 6.06 GHz-7.51 GHz. The results show that, relative to other antennas, this antenna has an isolation degree in the operating band greater than 13.1 dB. In addition, the antenna has good radiation characteristics and an acceptable envelope correlation coefficient.

The uniform geometrical theory of diffraction (UTD) calculating edge diffraction, creeping diffraction, and reflection, has been widely used to predict the shadowing problems for the beyond 5th generation. The limitation of the previous work, which only discussed the relationship between edge diffraction and reflection in the lit region, has motivated the analysis of the difference between creeping diffraction and edge diffraction in the shadowed region. In this paper, as the difference between creeping diffraction and edge diffraction from a dielectric circular cylinder and an absorber screen, respectively, a novel additional term is derived based on the UTD in the shadowed region. In addition, a uniform additional term using the Fock-type integral is proposed to unify the formulations in the lit and shadowed regions. The proposed uniform additional term is validated by the UTD and exact solutions of a dielectric circular cylinder at millimeter-wave or sub-terahertz bands. From the discussion of the results, the proposal can not only unify the formulations in the lit and shadowed regions but also eliminate the fictitious interference. Through the proposal, we can separate the contribution of the shadowed Fresnel zone number (FZ) and boundary conditions (i.e., the surface impedance and polarization). The frequency characteristics of the shadowed FZ and boundary conditions are analyzed and simulated near a shadow boundary at a high frequency (10 GHz-100 GHz). The results imply that there is almost no dependency (less than 1 dB) on boundary conditions in the lit region while there are few dependencies (more than 1 dB) on boundary conditions in the shadowed region. This work attempts to unify three different propagation mechanisms, i.e., reflection, edge diffraction, and creeping diffraction, by using one formula.

Fabrication of a non-planar helical antenna while maintaining mechanical stability and durability is always challenging. Moreover, impedance matching is an issue for helix-type antennas. To ease the fabrication challenge, the advantage of additive manufacturing is utilized. For achieving the self-matching, radiating spiral conductors in the forms of a strip and thick wire are used as two independent techniques. Consequently, a 3-turn hemispherical helical antenna (HHA) is chosen and analyzed by varying the width of the strip and the diameter of the wire. The better-performing HHA is again investigated including the effect of Poly-lactic acid (PLA) material-based supportive structure. The impacts of this extra support on antenna performance parameters are also investigated. At the initial step of fabrication, a 3-D printer is used to have the complete support structure. For ensuring the metallic part, copper strips and conductive paints are used as two different approaches. The measured data validates that both strip and wire-based HHA are self-matched. Circular polarization is obtained over wide frequency bands with axial ratio bandwidth (AR BW) of 35%. The maximum gain and beamwidths under 3-dB AR BW are 9.35 dBi and 118° respectively. The mechanically stable, low profile, and wideband circular polarization favored theuse of HHA in satellite communication.

This paper presents a novel fourth-order bandpass filter with high selectivity and out-of-band suppression based on equivalent magnetic side wall cavities (MSWCs). By loading a via hole into an MSWC to produce a zero mode as a non-resonating node and using the dual MSWC modes TEM₀₀₁ and TE₁₀₀ as resonant modes, a modified doublet with two poles and two transmission zeros (TZs) can be formed. Three types of frequency response, either quasi-elliptic or asymmetric, can be obtained and designed flexibly. The TZs can be located on both sides of the passband or both on just one side. The mechanisms for generating the TZs are analyzed, and the adjustment of the TZ positions is discussed. The proposed four-pole quasi-elliptic filter with four TZs is a cascade of two such doublets with two different types of asymmetric response. It has been fabricated and measured to validate the design. Comparison is made with some previous work on substrate integrated waveguide filters. The developed filter is free from radiation and relatively compact among high order filters with multiple adjustable TZs based on cascaded cavities of the substrate integrated waveguide type.

This letter presents a compact ultra-wideband circularly polarized (CP) crossed-dipole antenna with enhanced axial-ratio beamwidth (ARBW) and half-power beamwidth (HPBW). It consists of four modified arms which are fed by vacant-quarter phase delay rings to excite CP radiation. Four parasitic elements are utilized rotationally between the dipoles and the reflector. Not only does inducing vertical currents on the parasitic patches excite additional impedance resonance to realize an ultra-wideband operating, but also reinforced radiation is obtained to improve the ARBW and HPBW. The experimental results show that the proposed antenna realizes a -10 dB impedance bandwidth of 134.3%, and a 3 dB axial-ratio (AR) bandwidth of 115.0%, while holding a compact volume of 0.25λ_L × 0.25λ_L × 0.09λ_L (λ_L: wavelength at the lowest operating frequency). Furthermore, an HPBW and ARBW of more than 110° and 160° are realized within a broad operating band of 67.5% and 55.0%, respectively.

Moisture measurement in industrial applications, both in liquid and solid materials, presents a significant challenge. In the field of biofuels, this becomes even more critical. Among the various approaches developed for this purpose, indirect electromagnetic techniques have emerged as a valuable tool for accurately estimating moisture content. These techniques utilize the complex dielectric permittivity ε as an intermediary parameter, which is influenced by the water content in the material. As a first step toward this purpose, a 1''5/8 two-port coaxial transmission cell, developed at LNE-CETIAT, was studied to make dielectric measurements on liquids. Characterization and validation steps were requested to demonstrate the accuracy of this cell. For this purpose, an intra-laboratory comparison has been performed first at LNE-CETIAT using the 1''5/8 cell and the EpsiMu® coaxial cell - a fully validated reference tool. Then, an inter-laboratory comparison with the Fresnel Institute has been performed using a coaxial probe and another EpsiMu®cell. The measurements were carried out under identical ambient conditions, using liquid reference materials. In this work, the performance of the developed cell in the frequency band [0,1-1,1] GHz has been validated, as well as the accuracy of the three electromagnetic techniques used. The results of the experiments confirm the effectiveness of the 1''5/8 cell developed at LNE-CETIAT for measuring the dielectric properties of liquids.

The main challenges of designing an antenna for modern wireless communication are size reduction and mutual coupling. An ultra-wideband (UWB) multiple input multiple outputs (MIMO) antennae with four elements is suggested by this paper. Each element has two ports with dual-polarized patches to reduce the result of reciprocal coupling, increase the capacity, and keep a proper size. A circular geometric shape is in front of the patch of the proposed antenna to reduce the impact of mutual coupling. The CST STUDIO 2019 program simulates the single antenna element and MIMO antenna using the four integrated elements, eight integrated ports, and an Fr-4 insulating layer in an area of (70 x 70) mm². The MIMO antenna's operating frequency, which has a band of 2.85 (3.15-6) GHz at -10 dB, is 3.67 GHz while the operating frequency of a single antenna element, which has a band of 2.8 (3.1-5.9) GHz at -10 dB and a resonance return loss of -36 dB, is 3.64 GHz. The MIMO antennas obtained a diversity gain (DG) of about 10 with a good gain of about 8 dB while the envelope correlation coefficient (ECC) was equal to or less than 0.0001.

Dynamic Inductive Wireless Power Transfer (DIWPT), used for charging and powering electric vehicles (EVs), has been presented lately as a solution for increasing the distance range of electric vehicles and reducing the utilization of heavy and bulky battery systems. In most DIWPT designs, the voltage induced by the movement of the receiving coil over a time-varying magnetic field is neglected and never quantified. In this work, a simplified phasor expression for the total induced voltage on a coil that is moving in a sinusoidal time-variant magnetic vector field is developed. If no rotation is observed in the coil, a 90˚ out of phase voltage component proportional to the speed of the coil is added to the induced voltage that would be calculated if the coil was stationary. The phase of this voltage component is delayed or advanced with respect to the stationary induced voltage, according to whether the coil is moving into or out of a region of higher magnetic flux. Then, under some assumptions on the geometry of inductive coil configurations, it is possible to estimate the minimum induction frequency for which the quasi-stationary approximation can be considered. The resulting frequency value for a representative geometry is calculated, indicating that, for automotive applications, the relative error in the induced voltage is actually negligible, except in the vicinity of the points of zero-crossing in the magnetic flux, where the absolute value of the induced voltage is low anyway.

A hexagon-shaped fractal ultra-wideband (UWB) Multiple Input Multiple Output (MIMO) antenna is proposed in this paper for S (2 GHz to 4 GHz) and C (4 GHz to 8 GHz) band applications. The proposed design consists of two microstrip fed radiating elements of dimension 82 × 44 × 1.6 mm³. One rectangular stub and four resistance loaded stubs are introduced in the ground plane to reduce the mutual coupling between the radiators. These decoupling structures reduce the notches and enhance the isolation from -5 dB to -20 dB for the entire frequency range from 2.3 to 7.4 GHz. The performance characteristics and diversity parameters are also investigated which show the values of ECC < 0.004, DG > 9.96, CCL < 0.4 and MEG < 3 dB, and it is concluded that the proposed design is a good candidate for UWB MIMO. The proposed design is fabricated and tested which shows the close agreement between the simulated and measured results.

A four-port ultra-wideband (UWB) multi-input multi-output (MIMO) Vivaldi antenna loaded with resistance and rectangular radiation patch is designed and fabricated. The compact antenna consists of an improved ground and four microstrip feeders, with an overall size of 26 mm × 52 mm × 0.8 mm. The antenna adopts the resistance loading technology to absorb the excess electromagnetic waves in the low-frequency band and broaden the low-frequency bandwidth of the antenna. The rectangular radiation patch loading technique optimizes the main radiation direction and broadens the high-frequency bandwidth of the antenna. Meanwhile, T-slots and fence-type structures are etched on the ground plane, and I-stubs are added between microstrip feeders to reduce the antenna coupling and increase the isolation degree between the antenna ports. Simulation and experiments show that the impedance bandwidth of the MIMO antenna is 3.0~12.3 GHz; the isolation degree of the whole working bandwidth is higher than 15 dB; the envelope correlation coefficient (ECC) is smaller than 0.0125; and the increased diversity gain (DG) is more significant than 9.98 dBi. The antenna has good radiation performance and stable gain, which is suitable for applying the UWB MIMO system. This antenna has a particular reference significance for the research of the MIMO Vivaldi antenna.

In order to solve the problem of the influence of magnetic saturation and voltage source inverter (VSI) nonlinear factors on the parameter identification of permanent magnet synchronous wind generator (PMSWG), a variable neighborhood search-adaptive genetic algorithm (VNS-AGA) based on magnetic saturation and VSI compensation is proposed in this paper. Considering the existence of magnetic saturation, a mathematical model of PMSWG considering magnetic saturation is established. The least square method is used to identify the inductance of dq axis. The influence of VSI nonlinear factors on the system is regarded as a disturbance voltage, which is used as an electrical parameter; the parameters of PMSWG are identified simultaneously; and voltage compensation is carried out. After the accurate distortion voltage compensation mathematical model and fitness function are established, GA and adaptive algorithm are combined to increase the diversity of the population. Then variable neighborhood search (VNS) strategy is introduced to search the optimal region. Experimental results show that the proposed method is more accurate and convergent after considering magnetic saturation and on-line identification and compensation of disturbance voltage.

This paper proposes a coplanar L-strip feeding technique to excite the dominant transverse electric (TE) mode in a rectangular microstrip patch antenna. To excite the TE mode, the patch and ground layers are composed of artificial magnetic conductor (AMC) unit cells, and the L-strip is fashioned so that it is coplanar with the AMC patch layer. Two TE-mode microstrip patch antennas are full-wave analyzed and fabricated, one in which the AMC patch is centered with respect to the ground plane and one in which the AMC patch is shifted laterally with respect to the ground plane to improve radiation pattern symmetry. Results from the fabricated antennas are discussed and compared to the simulations. The proposed antennas successfully excite the dominant TE₁₀ mode while having at least 11% impedance bandwidth, 8 dBi gain, and stable broadside radiation patterns.

This paper presents an in-depth review of the performance improvement of antennas using metasurface. Metasurface is a periodic arrangement of perfect electric conductors (PECs) on a metal-backed dielectric substrate that do not exist in nature and are able to manipulate the behavior of electromagnetic (EM) waves incident on it. The manipulations of EM waves improve the performances in terms of impedance bandwidth, gain, size, specific absorption rate (SAR), radar-cross-section (RCS), and polarization conversions. Consequently, numerous recent works on metasurface-inspired antenna design and their theoretical perspectives on performance enhancements are discussed. By adopting the discussed theories, novel metasurfaces are developed and proposed that analyze impedance-bandwidth enhancement, gain enhancement and SAR reduction. For designing the metasurfaces, initially a conventional rectangular unit cell (CRUC) is theoretically developed using transmission line model at 2.45 GHz. Following that, the CRUC-based metasurface is incorporated with a monopole antenna, which enhanced the impedance-bandwidth from 140 MHz to 320 MHz and the gain from 2.5 dB to 7.4 dB. On the body, the presence of the metasurface retains all the performances as free space, with a reduced 1 g SAR of 0.034 and 10 g SAR of 0.024 W/Kg.

The paper proposes a antenna design that can serve as a comprehensive solution for covering 4G/5G cellular bands 850-1000 MHz, 1900 MHz, 2100-2700 MHz, 3300-4900 MHz, Global Navigation Satellite System (GNSS-L1) Band 1.56 GHz-1.61 GHz, V2X 5.850-5.925 GHz band which are appropriate for use in automobile applications. The proposed antenna is designed with respective polarization for cellular and GNSS applications, where the cellular antenna is linearly polarized, and the GNSS antenna is circularly polarized by chamfering the square patch. FR4 substrate material is used to construct the Long Term Evolution/4G (LTE) antenna. The optimization of the antennas ensures minimal coupling between them. The cellular antenna is designed using a hexagonal base with a modified ground plane to achieve the required cellular bands using a monopole (fractal design). The GNSS antenna is implemented on a PVC (Poly Vinyl Chloride) substrate. The measured results of S₁₁ parameter show that the proposed design covers all the required 4G/5G bands with minimum S₁₁ of -10 dB and a radiation pattern in the theta 60-90° range for cellular antenna, while the GNSS antenna has a zenith radiation pattern with axial ratio of <3 dB for theta angles in the 0-30° range and a mutual coupling of -15 dB. The fabricated antenna was measured to validate the simulated results of reflection coefficient, VSWR. All things considered, the suggested design is perfect for automobile applications to satisfy both satellite and mobile communication needs.