This study proposes a broadband, wide-angle metasurface for bistatic radar cross-section (RCS) reduction by integrating a low-profile bent-line unit design with an Adaptive Binary Particle Swarm Optimization algorithm enhanced by Array Pattern Synthesis (ABPSO-APS). The optimized metasurface achieves over 10 dB of bistatic RCS reduction across 8.4-21 GHz (86.7% fractional bandwidth), with a peak reduction of 22 dB, outperforming conventional checkerboard, genetic algorithm, and particle swarm optimization layouts by 22.82%, 15.27%, and 7.91%, respectively. The design also exhibits angular stability up to 30° and polarization insensitivity under both TE and TM incidences, while maintaining an ultrathin profile of only 0.1λ (where λ is the wavelength at the center frequency). These results demonstrate its strong potential as a compact and efficient solution for advanced electromagnetic stealth and radar signature control applications.

Supplying battery-free power to wireless sensor systems (WSS) mounted on rotating shafts remains a major challenge due to limited installation space, low rotational speed, and the requirement for long-term autonomous operation. This paper presents a compact dual-rotor energy harvester (EH) based on multilayer printed circuit board (PCB) sheets, designed for powering WSSs installed on ship propulsion shafts. Stacked multilayer PCB coils forming a three-dimensional structure are arranged on both the inner and outer rotors to enhance magnetic flux linkage and power density. The experimental results show that the EH generates power levels up to 959 mW at a shaft speed of 300 rpm. The output power improved nonlinearly with increasing rotational speed, demonstrating its suitability for real-time monitoring applications. The proposed EH offers a promising solution for powering WSS in autonomous driving technologies, with the potential for further optimization and integration into various mobility systems.

This work presents a dual-band circularly polarized antenna array in which adjacent elements are excited with quadrature phase progression using a cascaded hybrid-coupler feeding network comprising one rat-race coupler and two branch-line couplers. Double-T monopole elements enable dual-band operation, achieving impedance bandwidths of 300 MHz (2.4-2.7 GHz) and 975 MHz (5.025-6 GHz) with corresponding axial-ratio bandwidths of 110 MHz and 525 MHz. The array provides peak gains of 9.19 dB and 9.49 dB with simulated radiation efficiencies of 90% and 87% in the respective bands. The array yields peak realized gains of 9.19 dBic and 9.49 dBic with simulated total efficiencies of 90% and 87% in the corresponding bands. Unlike sequential rotation or multilayer CP arrays, the proposed single-layer planar hybrid-coupler network ensures frequency-stable dual band circular polarization. An analytical formulation of the array factor and axial ratio sensitivity is provided to clarify the CP synthesis mechanism and its suitability for compact vehicular platforms.

The phase noise levels of the output signals provided by two CRLH (Composite Right-/Left-Handed) distributed oscillator configurations are measured and compared. The first CRLH oscillator configuration provides two output signals, drain-line and gate-line output signals, available at the ends of the drain-line and gate-line that are not used for connecting the oscillator feedback. The second CRLH oscillator configuration is obtained by adding a Wilkinson power combiner to the first configuration that sums the drain-line and gate-line output signals for a single-output signal, a combined output signal. The experimental results show that the best performance in terms of output power and spectral purity can be obtained for the single-output CRLH oscillator.

In this letter, a frequency and linear polarization(LP) reconfigurable antenna is proposed. The antenna consists of two pairs of printed dipoles as the primary radiating patches. By independently controlling the direction of flowing current using loaded PIN diodes, the dynamic reconfiguration of both frequency and linear polarization (LP) can be realized. In addition, a dual-band artificial magnetic conductor (AMC) reflector is added under the radiator, which can effectively reduce the antenna profile to 0.1λ₀ (12.4 mm, where λ₀ is the wavelength at low operating frequency). Both simulated and experimental results show that the proposed antenna can operate in four modes: 0° LP low frequency (2.36-2.77 GHz) state, 0° LP high frequency (3.25-3.68 GHz) state, 90° LP low frequency state, and 90° LP high frequency state. The antenna exhibits stable radiation patterns, with gain values of 7.56 dBi in the low frequency state and 8.03 dBi in the high frequency state. This antenna is suitable for ISM band applications, such as Wi-Fi (2.4-2.48 GHz) and Bluetooth (2.4-2.48 GHz), as well as TDD Band 42, meeting the requirements of modern wireless communication systems.

This paper presents a compact two-layer diplexer based on a vertically stacked architecture with hybrid filtering, in which a dual-band bandpass power divider (PD) is integrated with low-pass (LPF) and high-pass filters (HPF). The design utilizes a double-layer dielectric substrate: the upper layer integrates a dual-band bandpass filter (BPF) and a Wilkinson PD, while the lower layer incorporates low-pass and high-pass filtering sections. Metallized vias and impedance-matching networks are employed to enable tight inter-layer coupling and ensure excellent electrical performance within a miniaturized footprint. The results indicate that the proposed diplexer achieves insertion losses below 4 dB and 4.5 dB in the two passbands (3.4-3.8 GHz and 4.7-5.0 GHz), respectively (including the inherent 3 dB loss of the power divider), input return losses exceeding 13 dB and 11 dB, respectively, approximately 45 dB out-of-band rejection at ±400 MHz from the passband edges, and inter-port isolation better than 30 dB. These characteristics satisfy the stringent requirements for multi-band co-site operation in 5G base stations and terminal devices.

This study presents a wideband dual-circularly polarized (dual-CP) antenna based on a distributed electromagnetic coupling mechanism. The antenna employed a circular slot structure fed by dual L-shaped microstrip lines. By introducing a rectangular protrusion on the ground plane and splitting it with a narrow slit, multiple parallel radiating paths were formed, establishing a distributed coupling mechanism. This mechanism introduces multiple resonant points to extend the impedance bandwidth (IBW) and generates multiple orthogonal components to enhance the axial ratio bandwidth (ARBW). The dual-port, left-right symmetric configuration enables dual-CP operation. The narrow slit decouples the shared current paths between the feeding structures, further enhancing the port isolation. Owing to its single-layer structure, the fabricated antenna achieves a low profile of only 0.011λ₀. Measured results show an IBW of 87.8% (2.98-7.65 GHz) and an ARBW of 66.9% (2.72-5.47 GHz). The proposed antenna achieves a wide bandwidth and low profile simultaneously, featuring a simple and easy-to-manufacture structure. Its operating band meets the requirements for coal mine communication systems.

High reliability and stability are essential for drive systems in intelligent inspection robots used in the power industry. To meet this requirement, this study investigates dual three-phase synchronous reluctance motors and proposes a five-leg fault-tolerant drive strategy based on direct-torque control (DTC). Unlike conventional dimension-reduction coordinate transformation methods that require isolating the faulty phase, which often leads to degraded system performance, the proposed approach introduces a bridge-arm sharing technique. By electrically coupling the faulty phase with a healthy phase, the spatial voltage vector distribution was reconstructed, enabling the reutilization of the faulty phase windings. Under single-phase fault conditions, the method effectively synthesizes the missing voltage vectors, preserves a circular flux linkage trajectory in the α-β subspace, suppresses 5th and 7th harmonics, and improves the current waveform quality. Simulation results verify that the strategy delivers superior harmonic suppression, reduced torque ripple, and enhanced system reliability, offering a novel technical pathway for fault-tolerant control of multiphase motors with strong potential for engineering applications.

This paper introduces an innovative antenna design for direct antenna modulation (DAM) applications in the 5G sub-6 GHz band. The antenna has a composite right/left-handed (CRLH) structure, an electromagnetic bandgap (EBG) made of Hilbert inclusions, and an artificial magnetic conductor (AMC) reflector. The AMC reflector reflects light with no phase shift at the design frequency, boosting forward gain to a maximum of 20 dBi at 5.59 GHz and reducing back lobes. One important new idea is to use integrated light-dependent resistors (LDRs) for photonic reconfiguration. This lets one change the antenna's impedance and resonant characteristics in real time. Changing the LDR states dynamically changes the antenna's gain in real time. For example, at 5.5 GHz, it can go from 10.11 dBi to 19.85 dBi. This makes it possible to do direct amplitude modulation without any outside modulators. Experimental results validate the effective implementation of DAM, demonstrating quantifiable alterations in channel capacity and bit error rate (BER) associated with varying antenna gain states. The suggested system shows a practical, adaptable antenna solution for modern adaptive communication systems.

In this paper, a semi-analytical method for the calculation of electromagnetic(EM) fields in horizontal multilayered media(HMLM) with full anisotropy is presented. First, the governing equation was obtained by plane wave decomposition to Maxwell's equations, and the EM fields in the wavenumber domain (WD) were solved by means of eigensystems. Subsequently, a more intuitive derivation of the spectral-domain propagation matrix method based on existing literature was employed for calculating WD's EM fields in the HMLM. Finally, the EM fields in the spatial domain (SD) were obtained by 2-D inverse Fourier transform. To accelerate the evaluation of SD's EM fields, 2-D infinite integrals were transformed into semi-infinite integrals including sine(cosine) functions by Euler's formula, and fast sine(cosine) transforms based on digital filters were introduced. It has been shown that the proposed semi-analytical method can be effectively used to calculate the EM fields in HMLM with full anisotropy through comparison with the existing numerical algorithm.

This paper presents an inverted F-shaped antenna with 40 × 25 × 1.6 mm³ dimensions designed for IoT applications. It can operate in the 2.45 GHz ISM (Industrial, Scientific, and Medical) band. This antenna was constructed on an FR-4 substrate, making it well-suited for wireless applications. The antenna consisted of a reverse F-shaped radiating structure with rectangular and circular slots to obtain enhanced bandwidth and suitable return loss. The proposed antenna achieved a simulated reflection coefficient of -19.17 dB at 2.45 GHz, with a bandwidth of 23.26 %. It also showed an acceptable radiation efficiency of 83.84% and a maximum gain of 3.40 dB.. This provided a bidirectional pattern of radiation which proves its quality in IoT applications. The antenna exhibited a slight difference between the simulation and measurement results, verifying its effectiveness. Moreover, the designed antenna is implemented in a home automation system to verify its validity in IoT application, and the results are highly significant.

This study offers a reduced device count (RDC) asymmetrical cross-connected seventeen-level T-type (CT-type) inverter. The proposed approach contains eight power switches, four self-voltage balancing capacitors and two direct current (DC) sources. The recommended architecture reduces the necessity to generate negative half-cycle for an H-bridge, hence minimizing the voltage stress across the switches. The capacitor and DC sources are cascaded with the switches to produce desired number of levels. Because of its substantial autonomy and high voltage balancing capability, this design is particularly beneficial to the integration of renewable energy sources into the grid. Pulse width modulation based on the level-shifted approach provides gate driver signals for the inverter circuit. A comparative analysis is undertaken to validate the efficacy of the suggested topology, which is differentiated from previously published topologies based on the number of DC sources, capacitor count, switches, drivers, and total standing voltage. Finally, the viability of the proposed topology is investigated by the simulated results and is further verified by a laboratory prototype. The total harmonic distortion (THD) of the voltage and current is obtained as 7.2% and 1.3% respectively.

This study proposes an independently controlled polarization rotator with transmissive and reflective capabilities operating in two different frequency bands. The proposed independently controlled transmissive and reflective polarization rotator (ICTR-PR) unit cell consists of four metal layers separated by three substrates. The transmissive polarization rotator mode is realized by two strips (receiving strips) on the top layer, which are connected with two vias through circular holes inside the ground plane to two 90° rotated strips (transmitting strips) on the bottom layer. The reflective polarization rotator mode was produced by connecting another pair of strips on the top layer to a microstrip line located in the middle layer. Properly adjusting the length of each strip allows both transmissive and reflective features to be independently controlled. The proposed rotator exhibits dual-frequency band resonances at 7.7 and 9.48 GHz for reflection and transmission responses, respectively. Furthermore, a high polarization conversion ratio (PCR) of more than 80% was achieved for both modes. A prototype was fabricated and measured to validate the simulation results. A good agreement between the experimental and simulated results was obtained.

This paper proposes a Luenberger-observer-assisted deadbeat predictive current control (LO-DPCC) scheme to compensate the inherent one-sample sampling/computation/PWM delay in embedded PMSM drives. A discrete time Luenberger observer is designed for the dq-axis current dynamics to provide a one-step-ahead current estimate, which is embedded into a closed form deadbeat predictive control law under a unified timing configuration. The method is evaluated by MATLAB/Simulink co-simulation using multi wheel steering actuator profiles (front wheel independent + rear wheel cooperative) and by DSP-based bench experiments at 10 kHz PWM. Compared with a tuned MPC-FOC baseline and an ESO-assisted DPCC benchmark under identical constraints, LO-DPCC consistently improves speed regulation and torque smoothness, indicating that observer based one-step prediction is an effective and implementation friendly approach for delay-compensated predictive current control of PMSM drives.

This article presents microwave detection and analysis of honey adulteration. A study of the differences between pure and adulterated honey based on dielectric properties in the frequency range of 2 to 12 GHz was performed. A honey adulteration determination system using a free-space method with microwaves was developed. The transmitting section was responsible for generating a 2.4 GHz frequency signal using a high-frequency signal generator and radiating the signal power through a prototype transmitting antenna that propagated through the honey sample to the receiving antenna. All 72 honey samples were tested and categorized into six levels of adulteration. The average transmission power (S₂₁) at adulteration levels of pure honey, 10%, 20%, and 50% was found to be 2.356, 2.321, 2.297, and 2.222 mV, respectively, with a coefficient of determination R² of 0.969. The sensitivity of the detection was 0.027 mV/10% adulteration. The decision-making system was used to test the measurement of 144 honey samples. The sensor system achieved an accuracy of 95.83%, indicating that the non-contact microwave-based method for detecting honey adulteration is effective.

A flexible semicircular ring slot antenna with an artificial magnetic conductor (AMC) structure for wireless body area network application is proposed in this paper. The AMC structure is an array of the double split ring resonator (DSRR) unit cells. According to the analysis of the DSRR unit cell, the volume of the AMC element is miniaturized for applications such as wearable technology. The measured impedance bandwidth of the proposed antenna is observed to be 2.34-2.61 GHz, which covers the 2.4 GHz Industrial Scientific Medical (ISM) band. The simulated half-power beamwidths are 81.1° and 70.1° in the E-plane and H-plane, respectively, and the front-to-back ratios are 17.51 dB in both the E-plane and H-plane. The calculated specific absorption rates (SARs) taken over the volume containing a mass of 1 g of tissue (U.S. standard) and 10 g of tissue (E.U. standard) are both less than the limitations. In conclusion, it is proper to use the proposed flexible antenna in wearable applications.

Two-way array factor is the product of array factors of transmitting array and receiving array in a radar antenna system. One of the major disadvantages of antenna arrays is undesirable high sidelobes near the main beam which causes ground clutter and interference in the radar system. Furthermore, increasing the number of array elements in transmitting/receiving modules results in a high complexity, cost, size, and weight. In this paper, a two-way radar structure with a receiving array that has only two elements is proposed to solve these aforementioned problems. Noticeably, all the existing receiving arrays have a number of elements that are much greater than two elements, and it is usually equal to or less than the number of transmitting array elements. Thus, this is the first time to produce such an extremely simple receiving array structure that has capability to provide low sidelobes and improved directivity in the resultant two-way array pattern. To demonstrate the flexibility and generality of the proposed two-way array structure, it is applied to the uniform array and non-uniform excitation array such as Dolph-Chebyshev as well as to electronic scanned arrays. Simulation results confirm the effectiveness and superiority of the proposed two-way structure where the highest sidelobe level reached -26.47 dB; the directivity was 25.96 dB; and the complexity of the receiving array was significantly reduced to only 12.5% when two separate non-existing elements were deployed and it was completely eliminated when two existing elements from the transmitting array were reused.

This paper presents a low-coupling ultra-wideband (UWB) antenna based on a metamaterial structure. The proposed metamaterial exhibits single-negative characteristics with a negative permittivity (ε) in the 3.3-4 GHz and 6.4-10.1 GHz bands, effectively reducing inter-element coupling. Through simulation and experimental measurement, the antenna is demonstrated to operate from 3.1 to 11.4 GHz, achieving an absolute bandwidth of 11.31 GHz and a relative bandwidth of 114.5% (S₁₁ < -10 dB). By integrating the metamaterial to suppress inter-element coupling, the antenna maintains low mutual coupling across the entire operating band (S₂₁ < -20  dB), with an envelope correlation coefficient (ECC) below 0.0045 and a radiation efficiency ranging from 70% to 95%. These outstanding performance metrics render the antenna well-suited for indoor high-precision positioning scenarios, providing stable and high-speed data transmission capabilities.

We present the design, fabrication, and experimental characterization of two 150 mm Luneburg lenses for X-band (10 GHz), produced by FFF using standard PLA. The printed PLA permittivity was measured with a 7 mm coaxial cell and EpsiMu, yielding ε_{r, PLA} ≈ 2.5 at 100% infill; a volume-weighted mixing model with perimeter correction was used to set discrete radial infill fractions. Two infill patterns (grid and gyroid) were tested, and waveguide mounts were integrated for reproducible alignment. Insertion-loss tests give 1.5 dB (grid) and 1.1 dB (gyroid) at 10 GHz. Far-field measurements (R = 1.5 m) and Friis-based estimates yield peak gains of 20.5 dBi (grid) and 19.4 dBi (gyroid) (simulation: 20.8 dBi); the waveguide reference gain is 4.9 dBi. Near-field tests at R = 0.15 m show an on-axis S₂₁ improvement of +2.33 dB, which corresponds to a low apparent near-field aperture efficiency (1.8-2.3%) while far-field efficiencies inferred from the measured gains are substantially higher (35-45%). These results confirm that discrete infill grading in low-cost FFF-printed PLA can realize effective Luneburg lenses at X-band, with quantifiable trade-offs among insertion loss, infill geometry, and realized aperture efficiency.

Flux observers have been extensively employed in the sensorless control of permanent magnet synchronous motors (PMSMs). Traditional flux observers are susceptible to DC offset and high-order harmonics during flux estimation. To address this issue, this paper proposes an improved third-order generalized integrator (TOGIFO-X), which combines a third-order generalized integrator with a low-pass filter. First, the relationship between the flux observation error and rotor position error is established. Then, through rigorous mathematical derivation and Bode-plot analysis, the proposed TOGIFO-X was compared with three conventional flux observers, demonstrating its capability to effectively eliminate both the DC component and high-order harmonic components in the estimated rotor flux without introducing any adverse effects on the amplitude or phase of the fundamental wave. Finally, the effectiveness of the improved third-order generalized integrator is verified via simulations and a 0.75  kW surface-mounted PMSM (SPMSM) experimental platform. The experimental results indicate that TOGIFO-X significantly enhances the reduction in flux estimation error and the elimination of DC bias, thereby contributing to improved position estimation accuracy and advances in sensorless control technology.