In this paper, a broadband bowtie-based log-periodic array antenna is proposed and investigated for 5G millimeter wave (mm-wave) applications. Using a Glass Integrated Passive Device (GIPD) process, the proposed antenna is implemented on a high dielectric constant glass substrate. To address the directional radiation issues associated with the traditional straight connection, the proposed antenna uses a crisscross connection effect with carefully spaced three dipole elements. Furthermore, the use of bowtie-based dipole offers a wide bandwidth advantage. The study also examines the effects of changes in key parameters on critical antenna features. The feeding structure uses a combination of coplanar waveguide (CPW) and microstrip line to strip line. For demonstration, a prototype antenna is optimized, fabricated and measured. The measurement results show that the 10 dB impedance bandwidth of the proposed antenna is from 21.5 to 36.1 GHz, and the gain is higher than 5.63 dBi.

The folding antennas are anticipated to become mandatory because of integration necesity according to communication object shapes. The effect of folded antennas on the electromagnetic (EM) radiation is an open question for RF and microwave wireless engineers. An innovative approach to explore the flexible patch antenna (FPA) parameters through V-folding analysis is addressed for this problem. This paper is focused on the methodological approach of FPA study by considering an innovative V-folding behaviour compared to the classical flat condition. As proof-of-concept, FPA prototypes are designed on Kapton substrate, simulated, fabricated, and tested. A non-shifting operating frequency is achieved at 3.4 GHz for all percentage-wise folding with a flat (unfold) bandwidth of about 360.8 MHz with good acceptable performance. The FPA performance prediction as reflection coefficient, efficiency, gain, and directivity versus forward and back V-folding percentage and angle is examined. The obtained result can be exploited to predict the V-folding effect on the communication performances of transceiver systems like radar, satellite and multimedia applications.

To ensure normal operation of a control system for a bearingless induction motor (BIM) after current sensor failure, a virtual current sensor (VCS) fault-tolerant control strategy was proposed. First, on the basis of the coordinate transformation of the stator current of the torque winding, the fault detection marks were set to realize current sensor fault detection. Second, according to the mathematical models of BIM, the stator current differential equations included in the VCS were derived, and the solutions of the equations were used as the reconstruction current of the fault current sensor, achieving fault-tolerant operation control after the sensor fault. The simulated and experimental results show that the set fault detection marks can realize the quick and accurate identification of sensor faults, and the estimated current from the VCS output can replace the faulty current after the current sensor fails, and the stator current can be reconstructed effectively under no-load, load change, and speed change conditions, and also ensure a good suspension of the motor rotor under sudden addition of disturbance condition.

This manuscript introduces an innovative customizable dual pole bandpass filter using a substrate-integrated waveguide technology on a conventional Rogers RT/Duroid 5880 high-frequency laminate. This structure is bifurcated into two identical cavity resonators to get the band stop-band pass-band stop behavior. The structure comprises lumped capacitors to indicate each resonator's operating frequency. Additionally, altering the capacitors in the proposed design facilitates the generation of the tunable dual pole in passband frequency, adding to its versatility. Further, measured and simulated results indicate that the design attains large tuning bandwidth, excellent insertion loss (better than 0.4 dB) and return loss (>22 dB), high Q-factor (11.8 to 16.87) with fractional bandwidth of 4.8% to 8.9% throughout the tuning range, affirming its practicality and functionality in X-band. A total of 12.3% of tunability is achieved from the structure.

This paper presents a compact loop-shaped omnidirectional rectenna for RF energy harvesting at 2.45 GHz and 5.8 GHz. Firstly, a loop-shaped antenna with iterated circular concave and convex structures is proposed to operate at both frequencies. Then, a rectifier circuit uses a complex impedance correlation matching technique to achieve high conversion efficiency. By connecting a piece of microstrip, two uncorrelated input impedances are transformed into a pair of conjugate impedances. In addition, by using a π-shaped structure with the same equivalent characteristic impedance and complementary equivalent electrical lengths at both frequencies, the pair of conjugate impedances are simultaneously matched to 50 Ω. The rectifier circuit is integrated in the loop-shaped antenna to form a compact dual-band rectenna. The overall size of the rectenna is 67.5 mm x 71.5 mm x 1.016 mm. The test results show that the S₁₁ of the antenna is -13.5 dB and -18.7 dB, and the peak conversion efficiencies of the rectenna are 65.1% and 38.4% at 2.45 GHz and 5.8 GHz, respectively. The simulated and tested results are quite similar.

A dual-port pattern diversity antenna is proposed in this letter for omnidirectional coverage. Two end-fire radiating beams are realized based on a two-element magnetic currents array. A folded half-mode substrate integrated waveguide (FHMSIW) is introduced to ensure that the distance between the two equivalent magnetic current radiation sources is about λ₀/4 (λ₀ is the wavelength in free space). When the two elements are driven by signals with a 90˚ or -90˚ phase difference, two end-fire radiation patterns with opposite directions can be realized. A prototype working at 2.425 GHz is fabricated and tested, achieving two independent end-fire radiation beams with a maximum gain of 4.3 dBi. Compared with conventional omnidirectional antennas, this work can effectively improve the gain of omnidirectional coverage based on a very compact structure.

This article delves into the strategic application of polarization diversity in Free-Space Optical (FSO) communication systems. With the overarching aim of optimizing data transmission and bolstering reliability, the paper explores the utilization of diverse polarization orientations to navigate the challenges posed by varying atmospheric conditions. By transmitting identical data streams through different polarization states, the impact of atmospheric turbulence is effectively mitigated, leading to enhanced signal quality and system dependability. This article sheds light on the theoretical underpinnings and simulation modeling of harnessing polarization diversity in FSO communication. The simulations conducted in this study using OptiSystem software ver. 17 demonstrate the effectiveness of this approach in mitigating the adverse impacts of atmospheric turbulence. Notably, the results consistently indicate that the integration of polarization diversity leads to lower Bit Error Rates (BER) across a spectrum of turbulence conditions. Furthermore, the proposed FSO system exhibits a remarkable ability to sustain robust communication capabilities over extended distances, outperforming the conventional system. Significantly, the proposed FSO system under weak, moderate and strong turbulence conditions achieves operational distances of approximately 4250, 3750 and 3200 meters, respectively compared to conventional system, which achieves distances of 3750, 3250 and 2250 meters, respectively. This significant performance disparity underscores the potency of the proposed FSO system in overcoming the challenges of atmospheric turbulence and extending the reach of optical communication.

Currently, various microwave filter designs contend for the use in wireless communications. Among several microstrip filter designs, the tunable filter presents more advantages and better prospects for wireless communication applications, being compact in size, cost effective, and light in weight. These reconfigurable microwave filters can reduce the number of switches between the electronic components. The number of switches among the electronic devices can be decreased using tunable BPF The tunable BPF is designed for X-band satellite communication applications as well as n77, n78, and n79 5G applications, and HSCH 3486 PIN diode is used to achieve the filter's tunability. An impedance bandwidth of 2.4 GHz and 2 GHz (fractional bandwidth of 25%) has been achieved with an S₂₁ less than -1.5 dB, -2 dB and S₁₁ of -22 dB and -31 dB at both the resonating frequencies. Semicircular cavity bandpass filter has been designed with the center frequency of 3.7 GHz. Switching between the two passbands has been obtained by attaching a PIN diode between the input and output feed lines.

The increased electrical demand in electrical machines promotes the improvement in power density in double stator systems. The power mapping performance and density of a novel type of interior embedded permanent magnet for a double-stator generator (IEDSG) is investigated in this work. This study investigates the basic attributes of the proposed IEDSG by analyzing various load resistances and changing rotor speeds. The Finite Element Method (FEM) is used to model the generation capabilities that consider electromagnetic properties such as flux density and flux lines. The proposed IEDSG is then manufactured and tested in a laboratory environment to assess how effectively it will perform when being paired with a load circuit. The efficiencies of two unique coil connections - series coil and independent coil - are evaluated and compared. According to the experimental results, when operating at an 800-rpm rotating speed, the independent-coil connection delivers a peak power output of 1688 W, a 16% improvement over the series-coil connection.

In this paper, a wideband circularly polarized (CP) filtering dielectric resonator antenna (FDRA) is proposed. The proposed antenna consists of a microstrip-Y-shaped slot line coupled feeding structure and a grooved DRA. The Y-shaped slot line not only serves as an energy coupling structure to excite the orthogonal modes (TE^x₁₁₁ mode and TE^y₁₁₁ mode) of DRA, forming the CP radiation effect, but also generates two resonant modes, thereby broadening the antenna impedance bandwidth. In addition, due to the groove engraved on the diagonal of the DRA top wall, the antenna CP performance within the passband is enhanced. Finally, by loading a shorting stub and a spur line on the microstrip feedline, radiation nulls are generated on both sides of the antenna passband, resulting in a quasi-elliptical filter response in the antenna gain curve. To further verify the performance of the antenna design, a prototype CP FDRA is fabricated and measured. The measurement results indicate that the antenna achieves a -10 dB impedance bandwidth of 46.1% (2.67-4.27 GHz) and an axial ratio (AR) bandwidth of 23% (3.08-3.88 GHz), with an average measured gain of approximately 4.9 dBi. This antenna exhibits high-frequency selectivity and an out-of-band suppression level exceeding 10 dB.

A novel planer, compact and quarter-wave transformer-coupled fed multi-band antenna is proposed and designed. The antenna uses a split-ring resonator (SRR) inspired ring metamaterial unit cell. The proposed ring metamaterial unit cell gives single negative (Epsilon negative) behaviour, which improves antenna performance. A partial ground and a quarter-wave transformer-coupled feed line are used to improve the impedance matching of the antenna. The antenna gives multi-band operation at resonating frequencies, 3.5, 8.5, and 13.7 GHz, with 2.9-4.5 GHz, 8.0-10.34 GHz, and 12.3-14.3 GHz, respectively. The maximum gains at resonating frequencies are 1.5 dBi, 4.1 dBi, and 6.5 dBi, with good impedance matching. The novelty of the antenna design is that the loading of the ring unit cell gives resonance at a much smaller wavelength than the resonant wavelength. The proposed antenna provides a miniaturized and multiband response compared to a conventional patch antenna.

Interrupted Sampling Repeater Jamming (ISRJ) can produce several false targets through intermittent sampling and forwarding of the intercepted signals. The paper proposes an interference identification and suppression method based on Short-Time Fourier Transform-Energy Distribution Correlation Judgment (STFT-EDCJ) to lessen the impact of the false targets mixed in echo pulses. Firstly, the method obtains the energy distribution of echoes in the time-frequency domain employing the short-time Fourier transform, extracts the time slice of higher energy targets through energy peak detection, and then calculates the Pearson correlation coefficient (PCC) of the energy distribution in the frequency domain of each target time slice to construct the Target PCC Datasets (TPCCD). Secondly, it distinguishes between the real target and false targets after echo pulse pressure by the range and specificity of TPCCD. Finally, it uses mapping the time domain position of the false targets to suppress interference. The abundant simulation results verify the proposed method's effectiveness, and the Monte Carlo simulation demonstrates the method's usefulness under ISRJ models.

In this brief, a dual-band filtering power divider (FPD) with high selectivity and independently controllable passbands is designed. The proposed FPD consists of asymmetric folded F-type resonators (AFFRs) and quarter-wavelength three parallel-coupled lines (TPCLs). The center frequencies of the dual bands can be determined by adjusting the physical lengths of AFFRs. Meanwhile, TPCLs can increase the transmission paths and introduce multiple transmission zeros (TZs) to achieve high selectivity. For demonstration, the proposed FPD is designed, fabricated, and measured. The center frequencies are 2.59/3.63 GHz with the 3-dB fractional bandwidths (FBWs) of 12.95% and 7.88%, and the isolation between port 2 and port 3 is better than 12.56/21.03 dB. The minimum insertion losses are better than 0.54/0.32 dB in each passband. The simulated results are compared with measured ones, and good agreement is realized.

This manuscript proposes a hybrid energy harvest and management system to manage harvested ambient thermal and radio frequency (RF) energy and provide constant voltage for an electronic water meter. It mainly includes an antenna, a rectifier, thermoelectric generators (TEGs), and an energy management circuit. The antenna harvests the ambient RF power, and the rectifier converts it to DC power. The harvested RF and thermal powers are stored in a capacitor and managed by an FEH710 energy management circuit to power an electronic water meter. Eight thermoelectric generators convert thermal energy into DC power. The proposed hybrid energy harvesting and management system has been evaluated by simulation and measurement. The antenna's reflection coefficient and peak gain at 2.45 GHz are -30 dB and 3.6 dBi, respectively. The rectifier's measured RF-DC power conversion efficiency (PCE) is 66.7% at 0 dBm. As a demonstration, a commercial electronic water meter worksstably by the harvested ambient RF and thermal energy. The proposed hybrid energy harvesting system is expected to find potential practical applications for the Internet of Things (IoT) in environments with RF radiation coverage and temperature gradients.

The internal structural details of unknown structures are very helpful to our personnel in carrying out activities during anti-terrorism operations and emergency disaster relief operations in urban environments. According to multipath identification and propagation mechanism separation technology, a building structure perspective imaging algorithm based on the ray-tracing model is proposed in this paper by making full use of the rich multipath delay power spectrum information and gradually filtering the multipath. Based on the imaging results taking overall consideration of all the propagation factors involved, the presented study is used to obtain the intricate geometric structure of indoor buildings. The original approach is then verified by using measured data, and the proposed algorithm is further optimized by extracting the internal wall structure of the building scene based on the Hough transform algorithm. In comparison with the real wall of the building, the average error of the inverse building wall position using simulated data is 0.071 m, and the average error of the inverse building wall position using the measured data is 0.355 m.

The electromagnetic characteristics analysis of the scattering signals from targets, which usually exist or are hidden in the surrounding environment, is one of the necessary prerequisites for the reliable reception of echo signals. Utilizing the GNSS signals as an opportunistic illumination source for detecting maritime targets has vast development prospect and scientific application value. GNSS signals, including GPS signals, are the right-hand circular polarization waves at L-band. Therefore, in this study, a comprehensive electromagnetic composite scattering model is established under circular polarization, which encompasses sea surface scattering, target single scattering, target multiple scattering, and coupled scattering between the target and sea surface. Then, the research investigates the variation characteristics of different scattering components (including the scattering of sea surface, the first, second, and third-order scattering of target, the total scattering of target, the coupled scattering of target induced by the reflection waves from sea surface, and the coupled scattering of sea surface induced by the reflection waves from target) in the composite scene under different polarizations, incident angles, wind speeds, and headings. The results indicate that the scattering of sea surface under LR polarization (which means that the polarization states of scattering and incident wave are left-hand circular polarization (LHCP) and right-hand circular polarization (RHCP), respectively) is significantly greater than that under RR polarization, while the opposite trend is observed for the target. Therefore, in the applications such as the detection and identification of ship targets on sea surface, it is better to choose the right-hand circular polarization channel to receive the scattering echo signal from target, which could effectively suppress the scattering echo of sea surface. These findings are of crucial significance in enhancing the effectiveness and accuracy of maritime target detection.

Wearable textile antennas have obtained remarkable attention in various medical fields due to their ease of integration and flexibility. This paper puts forward an Ultra Wide Band (UWB) Compact Textile Wearable Antenna (CTWA) for Wireless Body Area Network (WBAN) applications. The proposed antenna is a semicircular slotted elliptical antenna with an L shaped stub and a partial defected ground plane. The antenna is fabricated on denim jeans (ε_r = 1.77) and has an overall dimension of 27 × 28 × 0.7 mm with an operating frequency range 3.01-15.98 GHz, radiation efficiency of 83.5-90.11% and maximum gain of 5.81 dBi. Structural deformation studies including human body loading of the antenna are carried out, and the performance of the antenna is found to be stable. The proposed antenna has a low profile and high fractional bandwidth (137%) compared to the UWB wearable antennas reported in the literature. The calculated Specific Absorption Rate (SAR) of the antenna at the frequencies 4,7 and 10 GHz are 1.2, 1.06, and 1.58 W/Kg, respectively, which lies within the FCC (Federal Communications Commission) standard. The proposed CTWA is compact, flexible, wearable, and robust, which makes it suitable for on-body WBAN applications.

In this paper, a high gain antenna using Frequency selective Surface (FSS) is proposed. The compact structure is designed from a circular Ultra-wide band (UWB) monopole. Higher order modes of UWB antenna are suppressed by decreasing the thickness of the monopole, ground plane dimensions and increasing the gap between the ground plane and the monopole. Symmetrical portion of circular monopole is etched to form a semicircular monopole, and an off-set feed is employed. Dual band characteristics and miniaturization are achieved by etching horizontal and vertical slots and reducing ground plane dimensions. An FSS reflector is designed for gain enhancement. This miniaturized antenna offers less blockage and therefore, higher gain improvement when an FSS is used as a reflector.

In this paper, analytical formulas for tensor holographic impedance metasurface (THIMS) are presented to generate circularly polarized (CP) circular Airy orbital angular momentum (OAM) multibeams with flexibly independent control of the beam direction, polarization and OAM mode. As an example, a millimeter-wave THIMS is designed to generate CP circular Airy OAM dual beams: Beam-I: (θ1 = 0, φ1 = 0, LHCP, l = +1, 36 GHz), Beam-II: (θ2 = 0, φ2 = 0, RHCP, l = 0, 30 GHz). To the knowledge of the authors, for the first time, the THIMS generates circular Airy beams. Compared with the published metasurface on Airy beam, the created THIMS has the following advantages simultaneously: dual frequencies, dual CP, small size 30λ₀ at 30 GHz, high conversion efficiency (CE) (above 40%), long nondiffractive distance (ND) (up to 134.4λ₀), high OAM purity (above 89%), co-modulation for polarization, beam direction and OAM mode. The generated circular Airy OAM beams can be used in near-field scenarios such as high-efficiency wireless power transmission (WPT), high-capacity communication systems, and high-resolution imaging.

The THz spectrum (0.1-10 THz) is a region between optics and electronics, and it is still not fully explored and is unlicensed. Recent studies show that it will bring a revolution in technology, especially in the field of communication. Future communication technologies such as 6G and Terabit DSL will utilize this THz band as it has the capability to support high data rates in Tbps. For designing an efficient system that propagates these THz waves with low loss, it is required to understand the propagation channel properly. THz channel modeling is at its infancy stage, and a detailed investigation of channel behavior is required to study the efficient propagation of THz waves. In this study, the methods applied to the modeling of the THz channel are discussed in detail. Although channel modeling is a broad topic here only the methods and techniques are discussed along with their advantages and limitations. Lastly, the challenges and the future direction in the field of THz channel modeling are also discussed.