Search Results (142)

This study investigates the propagation characteristics and field distribution of photonic crystals composed of epsilon-near-zero (ENZ) materials and metal cylinders. The research reveals that the cutoff frequency of the photonic crystal formed by combining metal cylinders with an ENZ background is independent of the volume fraction of the metal cylinders and exhibits a stop-band profile within the measured frequency range. This unique behavior is attributed to the scattering of long-wavelength light when the wavelength approaches the effective wavelength range of the ENZ material. Taking advantage of this feature, the study selectively filters specific wavelength ranges from the mid-frequency band by varying the ratio of cylinder radius to lattice constant (R/a). Decreasing the R/a ratio enables the design of waveguide devices that operate over a broader guided wavelength range within the intermediate-frequency band. The findings emphasize the importance of the interaction between light and ENZ materials in shaping the transmission characteristics of photonic crystal structures. Full article

This paper presents the development and analysis of a planar microfluidic microwave sensor featuring three circular complementary split-ring resonators (CSRRs) fabricated on an RO3035 substrate. The sensor demonstrates enhanced sensitivity in characterizing liquids contained in a fine glass capillary tube by leveraging a novel configuration: a central 5-split-ring CSRR with a drilled hole to suspend the capillary, flanked by two 2-split-ring CSRRs to improve the band-stop filtering effect. The sensor’s performance is benchmarked against another CSRR-based microwave sensor with a similar configuration. High linearity is observed (R² > 0.99), confirming its capability for precise ethanol concentration prediction. Compared to the replicated square CSRR design from the literature, the proposed sensor achieves a 35.22% improvement in sensitivity, with a frequency shift sensitivity of 567.41 kHz/% ethanol concentration versus 419.62 kHz/% for the reference sensor. The enhanced sensitivity is attributed to several key design strategies: increasing the intrinsic capacitance by enlarging the effective area and radial slot width to amplify edge capacitive effects, adding more split rings to intensify the resonance dip, placing additional CSRRs to improve energy extraction at resonance, and adopting circular CSRRs for superior electric field confinement. Additionally, the proposed design operates at a lower resonant frequency (2.234 GHz), which not only reduces dielectric and radiation losses but also enables the use of more cost-effective and power-efficient RF components. This advantage makes the sensor highly suitable for integration into portable and standalone sensing platforms. Full article

This study proposes a novel control framework for semi-active seat suspensions, specifically targeting motion sickness mitigation through precision suppression of vertical vibrations within the 0.1–0.5 Hz frequency range. Firstly, a fractional-order band-stop filter in conjunction with a linear quadratic regulator (LQR) controller under frequency-domain sensitivity constraints (0.1–0.5 Hz) is proposed to achieve frequency-selective vibration attenuation. Secondly, the multi-objective butterfly optimization algorithm (MOBOA) is adopted to optimize the LQR controller’s weighting matrices (Q, R) by balancing conflicting requirements in terms of human body displacement limits, acceleration thresholds, and suspension travel. Finally, experimental validation under concrete pavement excitation and random road profiles demonstrates significant advantages over conventional LQR, i.e., a 41.04% reduction in vertical vibration amplitude and a 55.95% suppression of acceleration peaks within the target frequency band. The combined enhancements offer dual benefits of enhancing ride comfort and motion sickness mitigation in real-world driving scenarios. Full article

This paper presents a simulation-based investigation of passive frequency tunability in frequency-selective surfaces (FSSs) enabled by Moiré pattern interference. By overlapping two identical hexagonal FSS layers and introducing rotational misalignment between them, we demonstrate that the resulting Moiré patterns induce significant shifts in the resonance frequency without any external bias or active components. Using full-wave simulations in HFSS, we show that rotating the second layer from 0° to 30° can shift the resonant frequency from 4.4 GHz down to 1.2 GHz. This tunable behavior emerges solely from geometrical manipulation, offering a low-complexity alternative to active tuning methods that rely on varactors or micro-electromechanical systems (MEMSs). We discuss the theoretical basis for this tuning mechanism based on effective periodicity modulation via rotational interference and highlight potential applications in passive reconfigurable filters and refractive index sensors. The proposed approach provides a promising route for implementing tunable electromagnetic structures without compromising simplicity, power efficiency, or integration compatibility. Full article

The inherent randomness and intermittency of offshore renewable energy sources, such as wind and solar power, pose significant challenges to the stable and secure operation of the power grid. These fluctuations directly affect the performance of grid-connected systems, particularly in terms of harmonic distortion and load response. This paper addresses these challenges by proposing a novel harmonic control strategy and load response optimization approach. An integrated three-winding transformer filter is designed to mitigate high-frequency harmonics, and a control strategy based on converter-side current feedback is implemented to enhance system stability. Furthermore, a hybrid PI-VPI control scheme, combined with feedback filtering, is employed to improve the system’s transient recovery capability under fluctuating load and generation conditions. Experimental results demonstrate that the proposed control algorithm, based on a transformer-oriented model, effectively suppresses low-order harmonic currents. In addition, the system exhibits strong anti-interference performance during sudden voltage and power variations, providing a reliable foundation for the modulation and optimization of offshore wind–solar coupled hydrogen production power supply systems. Full article

In this paper, a miniaturized broadband bandstop filter with a simple structure is proposed, synthesized, and developed. The proposed broadband bandstop filter is designed using asymmetrically loaded parallel-coupled microstrip lines, resulting in five transmission zeros within the stopband. Closed-form formulas of the entire set of generated transmission zeros are derived to guide a practical design procedure. To demonstrate the effectiveness of the proposed concept and synthesis method, a miniaturized broadband bandstop filter centered at 3 GHz with a 20 dB rejection bandwidth of about 100% is designed, fabricated, and measured. The core circuit size of the developed broadband bandstop filter is only 0.5 λ_g × 0.1 λ_g (31.2 mm × 6.5 mm). Full article

In modern optical coating production, optical monitoring technology is an indispensable component. The traditional monochromatic monitoring technology used in current commercial and research institutions is usually only for a specific wavelength and cannot fully represent the characteristics of the film in the entire spectral range. Moreover, for non-quarter-wave coating systems (such as multilayer or complex coating systems), a thickness change in a single coating may have a significant effect on the performance of the entire coating system. In this case, it may be difficult to use monochromatic monitoring to accurately determine the thickness of each layer, resulting in reduced monitoring accuracy. At present, although broadband optical monitoring can be monitored over a wide wavelength range, the stop-plating time may be misjudged due to error accumulation during the coating process. To solve these problems, a broadband optical monitoring method with an improved error compensation mechanism is proposed in this paper. An optimal function that combines the absolute error and shape similarity of the transmission spectrum is designed, and the transmission spectrum is optimized by the limited random search method. In addition, a breakpoint algorithm based on parabolic error curve prediction is designed for the first time in this paper, which avoids the problem of excessive deposition thickness encountered by traditional broadband monitoring methods in the automatic coating processes. To verify the effectiveness of the proposed method, a set of hardware verification platforms based on broadband optical monitoring is designed in this paper, and a 30-layer shortwave-pass filter is constructed as an example. Compared with the traditional time monitoring method (CTMM), the proposed broadband optical monitoring method (PBMM) has significant advantages in terms of the matching degree between the transmission spectrum and the target spectrum, as well as the average transmittance in the low-pass band. In summary, the broadband optical monitoring method with an improved error compensation mechanism proposed in this paper provides an effective solution for high-precision optical coating production and has high practical application value and research significance. Full article

We designed and investigated a plasmonic nanosensor with ultra-high sensitivity and tunability, which is composed of a metal–insulator–metal (MIM) waveguide integrated with a side-coupled resonator (SR) and metal baffle. Its high performance is derived from Fano resonance, which is generated by the interaction between the modes of the SR and the baffle, and it can be precisely tuned by adjusting the parameters of the SR. Further investigation based on the incorporation of a side-coupled rectangular-ring resonator (SRR) generates three distinct Fano resonances, and the Fano resonance can be accurately tuned by manipulating the parameters of the resonators within the system. Our proposed plasmonic system can serve as a highly sensitive refractive index nanosensor, achieving a sensitivity up to 1150 nm/RIU. The plasmonic structures featuring independently tunable triple Fano resonances open new avenues for applications in nanosensing, bandstop filtering, and slow-light devices. Full article

In this paper, a novel multiple-input operational transconductance amplifier (MI-OTA) is proposed. The MI-OTA can be obtained by using the multiple-input bulk-driven MOS transistor (MIBD MOST) technique. The circuit structure is simple, can operate with a supply voltage of 0.5 V, and consumes 937 pW at a current setting of 625 pA. The proposed MI-OTA was used to implement a high-order multiple-input voltage-mode universal filter. The proposed filter can provide non-inverting and inverting low-pass, high-pass, band-pass, band-stop, and all-pass transfer functions to the same topology. In addition, it has a high input impedance and does not need any inverted input signals, so there is no additional buffering circuit. The proposed filter can be used for biological signal processing. The proposed MI-OTA and the second-order universal filter were simulated in Cadence using CMOS process parameters of 0.18 μm from TSMC to verify the functionality and performance of the new structures. Full article

This paper presents a multiple-input single-output (MISO) shadow filter implemented using multiple-input differential difference transconductance amplifiers (MI-DDTAs). The MI-DDTA’s multiple inputs are realized through the multiple-input bulk-driven MOS transistor (MI-BD MOST) technique. Leveraging the multiple-input capability of the DDTA, various filter responses—low-pass filter (LPF), high-pass filter (HPF), band-pass filter (BPF), band-stop filter (BSF), and all-pass filter (APF)—can be efficiently achieved by appropriately configuring the input signals. The natural frequency and quality factor of the shadow filter can be independently tuned using external amplifiers. Unlike conventional shadow filters, where adjusting the quality factor or natural frequency impacts the passband gain, this design ensures a constant unity passband gain. The MI-DDTA operates at a supply voltage of 0.5 V and consumes 385.8 nW of power for setting current I_set = 14 nA. The proposed MI-DDTA and shadow filter are designed and validated through simulations in the Cadence design environment, using a 0.18 µm CMOS process provided by TSMC (Taiwan Semiconductor Manufacturing Company Limited). Full article

The transmittance characteristics and the band structure of photonic heterostructures consisting of four distinct dielectric materials are analyzed using the transfer matrix method. An enhanced band structure of such crystals is discovered. It is shown that the band structure is strongly influenced by the arrangement of unit cells in the periodic building blocks of the crystals. The transmission spectra are evaluated for varying layer thicknesses and incident angles to investigate their impact on wave propagation. The symmetrical results for periodicities, sub-layer thickness, and oblique incident angles indicate robust bandgaps with blue shifting and enhanced transmission. Moreover, the periodicity in different cases, followed by the period, has also shown to have a great impact on the emergence of multiple bandgaps. The photonic bandgap and frequency are associated with the lattice elements of the unit cell, shifting naturally as a fundamental property of the structure, which has been achieved by the alteration of unit cells. Hence, the proposed photonic heterostructures offer significant potential for developing efficient band-stop and band-pass filters, facilitating their use in multi-functional integrated optical circuits within the Terahertz spectrum. Full article

This paper presents a low-voltage, low-power current differencing transconductance amplifier (CDTA) utilizing the bulk-driven MOS transistor technique in the subthreshold region for reduced voltage and power consumption. The proposed CDTA includes a z-copy terminal, which enhances its functionality in current-mode circuit applications. Designed in the Cadence Virtuoso environment using 0.18 µm CMOS technology from Taiwan Semiconductor Manufacturing Company (TSMC), the amplifier operates with a supply voltage of 0.45 V and consumes 328 nW of power, with a bias current set to 10 nA. The current bandwidth and offset of the CDTA are 35 kHz and 0.3 nA, respectively. To demonstrate its performance, the CDTA is applied in a current-mode universal filter, which can realize low-pass, band-pass, high-pass, band-stop, and all-pass responses within a single topology. This design eliminates issues related to inverting input signals, input signal matching, or the need for multiple input signals. Additionally, the natural frequency of these filtering functions can be electronically controlled. The low-pass filter achieves a dynamic range of 61 dB, with a total harmonic distortion of 0.8%. Full article

This study introduces a motion-sickness-reducing control strategy aimed at enhancing ride comfort in Electric Autonomous Vehicles (EAVs). For lateral control, the forward look-ahead distance was adaptively adjusted based on the Motion Sickness Dose Value (MSDV) analysis from ISO 2631-1, effectively mitigating lateral acceleration and its motion-sickness-related frequency components, leading to a reduced MSDV. For longitudinal control, Linear Quadratic Regulator (LQR) optimal control was applied to minimize acceleration, complemented by a band-stop filter specifically designed to attenuate motion-sickness-inducing frequencies in the acceleration input. The bandwidth of the band-stop filter used in this study was designed based on the motion-sickness frequency weighting specified in ISO 2631-1. The simulation results of the proposed control indicate a significant reduction in MSDV, decreasing from 16.3 to 10.46, achieving up to a 35.8% improvement compared to comparative control methods. While the average lateral position error was slightly higher than that of the comparative controller, the vehicle consistently maintained lane adherence throughout path-following tasks. These findings underscore the potential of the proposed method to simultaneously mitigate motion sickness and achieve a robust path-following performance in autonomous vehicles. Full article

Rotor motor fault diagnosis in Unmanned Aerial Vehicles (UAVs) presents significant challenges under variable speeds. Recent advances in deep learning offer promising solutions. To address challenges in extracting spatial, temporal, and hierarchical features from raw vibration signals, a hybrid CNN-BiLSTM-MHSA model is developed. This model leverages Convolutional Neural Networks (CNNs) to identify spatial patterns, a Bidirectional Long Short-Term Memory (BiLSTM) network to capture long- and short-term temporal dependencies, and a Multi-Head Self-Attention (MHSA) mechanism to highlight essential diagnostic features. Experiments on raw rotor motor vibration data preprocessed with Butterworth band-stop filters were conducted under laboratory and real-world conditions. The proposed model achieves 99.33% accuracy in identifying faulty bearings, outperforming traditional models like CNN (93.33%) and LSTM (62.00%) and recent advances including CNN-LSTM (98.87%), the Attention Recurrent Autoencoder hybrid Model (ARAE) (66.00%), Lightweight Time-focused Model Network (LTFM-Net) (96.67%), and Wavelet Denoising CNN-LSTM (WDCNN-LSTM) (96.00%). The model’s high accuracy and stability under varying conditions underscore its robustness, making it a reliable solution for rolling bearing fault diagnosis in rotor motors, particularly for dynamic UAV applications. Full article

Terahertz is one of the most promising technologies for high-speed communication and large-scale data transmission. As a classical optical component, ring resonators are extensively utilized in the design of band-pass and frequency-selective devices across various wavebands, owing to their unique characteristics, including optical comb generation, compactness, and low manufacturing cost. While substantial progress has been made in the study of ring resonators, their application in terahertz surface wave systems remains less than fully optimized. This paper presents several spoof surface plasmon polariton-based devices, which were realized using ring resonators at terahertz frequencies. The influence of both the radius of the ring resonator and the width of the waveguide coupling gap on the coupling coefficient are investigated. The band-stop filters based on the cascaded ring resonator exhibit a 0.005 THz broader frequency bandwidth compared to the single-ring resonator filter and achieve a minimum stopband attenuation of 28 dB. The add–drop multiplexers based on the asymmetric ring resonator enable selective surface wave outputs at different ports by rotating the ring resonator. The devices designed in this study offer valuable insights for the development of on-chip terahertz components. Full article