Search Results (477)

While circuit parameter optimization has matured significantly, the systematic discovery of novel circuit topologies remains a bottleneck in analog design automation. This work presents SymXplorer, an open-source Python framework designed for automated topology exploration through symbolic modeling of analog components. The framework enables a component-agnostic approach to architecture-level synthesis, integrating stability analysis and higher-order filter exploration within a streamlined API. By modeling non-idealities as lumped parameters, the framework accounts for physical constraints directly within the symbolic analysis. To facilitate circuit sizing, SymXplorer incorporates a multi-objective optimization toolbox featuring Bayesian optimization and evolutionary algorithms for simulation-in-the-loop evaluation. Using this framework, we conduct a systematic search for differential Common-Gate (CG) Bandpass Transimpedance Amplifier (TIA) topologies tailored for 5G New Radio (NR) Radio-over-Fiber applications. We propose a novel, orthogonally tunable Bandpass TIA architecture identified by the tool. Implementation in 65 nm CMOS technology demonstrates the efficacy of the framework. Post-layout results exhibit a tunable gain of 30–50 dB$\Omega$, a center frequency of 3.5 GHz, and a tuning range of 500 MHz. The design maintains a power consumption of less than 400 $\mathsf{\mu }$W and an input-referred noise density of less than 50 pA/$\sqrt{\mathrm{Hz}}$ across the passband. Finally, we discuss how this symbolic framework can be integrated into future agentic EDA workflows to further automate the analog design cycle. SymXplorer is open-sourced to encourage innovation in symbolic-driven analog design automation. Full article

Defect modes in phononic crystals (PnCs) provide strongly localized resonances that are essential for frequency-dependent wave filtering and highly sensitive sensing. Their functionality increases greatly when their spectral characteristics can be externally tuned without altering the structural configuration. However, existing feedback control strategies rely on laminated piezoelectric defects, which have uniform electromechanical loading that causes voltage cancellation for even-symmetric defect modes. Consequently, only odd-symmetric defect bands can be manipulated effectively, which limits multi-band tunability. To overcome this constraint, we propose a segmented piezoelectric sensor–actuator design that enables symmetry-dependent feedback at the defect site. We develop a transfer-matrix analytical framework to incorporate complex-valued feedback gains directly into dispersion and transmission calculations. Analytical predictions demonstrate that real-valued feedback yields opposite stiffness modifications for odd- and even-symmetric modes. This enables the simultaneous tuning of both defect bands and induces an exceptional-point-like coalescence. In contrast, imaginary feedback preserves stiffness but modulates effective damping, generating a parity-dependent amplification-suppression response. The analytical results closely match those of fully coupled finite-element simulations, reducing computation time by more than two orders of magnitude. These findings demonstrate that segmentation-enabled feedback provides an efficient and scalable approach to tunable, multi-band, non-Hermitian wave control in piezoelectric PnCs. Full article

The Lyot filter, a fundamental element of the Yunnan Observatories Coronagraph Green-line Imaging System (YOGIS) at Lijiang Observatory, utilizes a Liquid Crystal Variable Retarder (LCVR) for swift electrical modulation. This filter allows for precise observations of the coronal green line (Fe XIV, central wavelength 5303 Å) with a narrow full-width at half-maximum (FWHM) of 1 Å and enables rapid adjustment of the transmission band wavelength. This feature aids in capturing the sky background intensity around the green line and images of two line wings (offset by $\pm 0.45$ Å from the central wavelength), crucial for determining the green line’s Doppler shift. By employing sky background subtraction and processing line wing images, an improved signal-to-noise ratio (SNR) in coronal green line images is achieved. The YOGIS Lyot filter, an enhancement of the NOrikura Green-line Imaging System (NOGIS) filter, operates at a wavelength of 5303 Å, offers a wavelength tuning range of $\pm 2$ Å, and tunes within <60 ms. This study elucidates the filter’s design principles, outlines essential calibration procedures, and validates its performance through on-site observations using the YOGIS. Full article

To mitigate the pervasive noise interference present in the measured vibration signals of radial steel gates and to address the limitations of conventional wavelet-threshold denoising, this study proposes a coupled “decomposition–denoising” theoretical framework for vibration-signal purification. The key novelty lies in a smooth and tunable thresholding strategy that enables controlled filtering while preserving key structural characteristics within an integrated denoising workflow. In the proposed approach, the measured signal is decomposed into intrinsic mode components using a data-driven decomposition method, noise-dominated components are identified using multiscale permutation entropy, and only these components are selectively denoised before signal reconstruction. Both qualitative and quantitative analyses conducted on synthetic signals demonstrate the effectiveness of the proposed framework and confirm the enhanced smoothness and robustness of the improved thresholding scheme. Performance is evaluated using objective measures such as signal-to-noise ratio and root-mean-square error, together with spectral-consistency checks for field measurements. Furthermore, two field-measured engineering cases involving radial steel gates substantiate the engineering applicability and generalization capability of the proposed method, showing clearer signals and more stable diagnostic-relevant indicators. Finally, the study integrates the decomposition, denoising, and parameter-selection modules into a user-oriented vibration-signal denoising system, establishing an efficient workflow for engineering signal processing and subsequent structural-health monitoring applications. Full article

This work presents a notch filter architecture based on a dual-output second-generation voltage conveyor, designed with a current-mode approach. The proposed topology employs a single frequency-selective LC branch and directly uses the two voltage outputs of the DOVCII to generate a notch response without additional active stages. Analytical expressions for the transfer function, notch frequency, and quality factor are derived, highlighting independent control of the passband gain and notch parameters. A sensitivity analysis demonstrates that the notch frequency depends exclusively on the LC product with half-order sensitivities, while the quality factor is predominantly controlled by a single resistor, resulting in predictable tuning and improved tolerance to passive component variations. Transistor-level analysis of the proposed filter was carried out using a standard AMS 0.35 μm CMOS process and has been validated through both circuit-level simulations and experimental measurements using a DOVCII implementation based on the AD844 current-feedback amplifier. Prototypes operating at 100 kHz and 50 Hz notch frequencies have been implemented, the latter employing a current-mode inductance simulator to avoid bulky passive inductors. Full article

Previous studies on reconfigurable intelligent metasurface (RIS) design have primarily relied on full-wave electromagnetic simulation software, which often incurs high computational costs and lacks clear design direction. The design of multi-bit RIS remains challenging and there is currently no suitable systematic method for selecting the corresponding tuning devices. To overcome these limitations, this article proposes a novel equivalent circuit-based approach to RIS design. In contrast to the conventional approach, where the equivalent circuit model is derived from post-design evaluation of the scattering properties of RIS, our work is entirely driven by the equivalent circuit model from the outset to accomplish the unit cell design. A complete workflow as well as details of each constituent step are presented for the topology design of RIS based on equivalent circuit topology. Building on this circuit topology, a 3-bit reflective phase reconfigurable unit cell is developed based on a tunable band-stop filter circuit. We conducted adjustable phase verification experiments and beam deflection experiments. The consistency between the experimental results and circuit theory demonstrates the feasibility and practicality of the equivalent circuit method of RIS design. This circuit-to-structure methodology provides a physically interpretable and systematic framework for designing RIS with arbitrary electromagnetic responses, offering new insights into RIS design. Full article

Contaminated water detoxification remains difficult due to the presence of persistent halo-organic contaminants, such as perfluorooctanoic acid (PFOA) and chlorophenols, which are chemically stable and resist conventional purification methods. Functionalized membrane-based separation and decontamination have garnered immense attention in recent years. Commercially available microfiltration membrane (PVDF) and polymeric non-woven fiber filters (glass and composite) are functionalized with poly(methacrylic acid) (PMAA) that shows outstanding pH-responsive performance and tunable water permeability under ambient conditions perfect for environmental applications. Polymer loading based on weight gain measurements on PMAA–microglass composite fibers (137%) and microglass fibers (116%) confirmed their extent of functionalization, which was significantly greater than that of PVDF (25%) due to its widely effective pore diameter. Presence of chemically active hydrogel within PVDF matrix was validated by FTIR (hydroxyl/carbonyl) stretch peak, substantial decrease in contact angle (68.8° ± 0.5° to 30.8° ± 1.9°), and decrease in pure water flux from 509 to 148 LMH/bar. Nanoparticles are generated both in solution and within PVDF using simple redox reactions. This strategy is extended to PVDF-PMAA membranes, which are loaded with Fe/Pd nanoparticles for catalytic conversion of 4-chlorophenol and PFOA, forming Fe/Pd-PVDF-PMAA systems. A total of 0.25 mg/L Fe/Pd nanoparticles synthesized in solution displayed alloy-type structures and demonstrated a strong catalytic performance, achieving complete hydrogenation of 4-chlorophenol to phenol and 67% hydrogenation of PFOA to its reduced form at 22–23 °C with ultrapure hydrogen gas supply at pH 5.7. These results underscore the potential of hybrid polymer–nanoparticle systems as a novel remediation strategy, integrating tunable separation with catalytic degradation to overcome the limitations of conventional water treatment methods. Full article

Surface Plasmon Resonance imaging (SPRi) is a powerful label-free technique for high-throughput biochemical analysis. Wavelength modulation is particularly suitable for SPRi due to its wide dynamic range and robustness to fabrication tolerances. However, conventional systems relying on tunable filters (e.g., AOTF, LCTF) suffer from high cost, complexity, and limited temporal resolution. To overcome these drawbacks, we developed a rapid wavelength-modulation SPRi system using a multi-LED source and an adaptive second-order fitting (ASF) algorithm. The system covers the 730–805 nm spectrum with five LEDs. The ASF algorithm first performs a coarse full-spectrum scan to locate the resonance wavelength, then dynamically selects an optimal three-LED subset for fast second-order fitting, enabling accurate reconstruction of resonance wavelength without mechanical scanning. This approach significantly reduces cost and complexity while achieving a scanning cycle of 105 ms, RI resolution of 5.54 × 10⁻⁶ RIU, dynamic range of 0.0241 RIU, and excellent multi-channel consistency. The system has been successfully applied to monitor multi-channel antibody–antigen interactions in real time. Furthermore, it was used to detect cartilage oligomeric matrix protein (COMP) in synovial fluid, where an elevated concentration in an osteoarthritis sample versus a control aligned with its role as a cartilage catabolism marker. This work validates a practical and reliable platform for early diagnosis of osteoarthritis. Full article

This study presents an in-depth investigation of an eccentric double-ring microwave resonator comprising two asymmetrically coupled conductive loops connected at a single point. The configuration was systematically analyzed using analytical modeling, full-wave electromagnetic simulations (Ansys HFSS), and experimental characterization. Analytical formulations based on the resonant condition of thin conductive rings provided theoretical estimates of the fundamental and higher-order eigenmodes, while simulations yielded accurate resonance frequencies, transmission responses, and electric field distributions. The transmission coefficient (S₂₁) exhibited two distinct resonance dips at 436 MHz and 708 MHz, confirming strong inter-ring coupling and hybrid mode formation. Electric field mapping revealed pronounced confinement within the resonator region (E > 170 V/m) and substantial attenuation of the transmitted field (E < 13 V/m), demonstrating efficient electromagnetic energy suppression. Experimental results showed excellent consistency with theoretical predictions. This paper aims to establish a compact, low-cost, and tunable resonant structure capable of frequency-selective attenuation and field confinement without using lossy materials. Unlike conventional symmetric resonators, the eccentric configuration enables enhanced coupling control and modal diversity, making it highly relevant for the design of next-generation electromagnetic shielding, filtering, and sensing systems. Full article

This study explores the tunable characteristics of optical Tamm states (OTS) in a metal–distributed Bragg reflector (DBR) structure integrated with a monolayer of molybdenum disulfide (MoS₂). Through finite element simulations, we demonstrate that incorporating MoS₂ enhances electromagnetic field localization at the metal–DBR interface, facilitating enhanced exciton–photon interaction. As the number of DBR periods increases, the OTS resonance wavelength undergoes a blue shift and eventually stabilizes, which indicates a wavelength-locking behavior. Under external bias, the locking threshold is lowered, and the resonance wavelength exhibits a nearly linear blue shift of approximately ~1 nm/V. Moreover, absorptance varies non-monotonically with the metal thickness, reaching over 99% at a thickness of 25 nm, due to the combined effects of plasmonic confinement and MoS₂ excitonic enhancement. These findings demonstrate the potential of this structure for application in tunable photonic devices such as optical filters and modulators. Full article

Low-frequency noise, the most critical noise frequency band affecting human physical and mental health, poses a significant challenge for effective control in spatially constrained building environments. The shunt loudspeaker offers a novel solution to control low-frequency noise. Unlike traditional methods, it does not rely on large cavity depth but only requires the adjustment of parameters or structure of the shunt circuit. However, most shunt loudspeakers utilize analog shunt technology, which leads to instability and inaccuracy owing to the negative impedance converter circuit and parasitic impedance in analog electronic components. The paper proposes a tunable low-frequency sound absorber utilizing a combined array of hybrid digital–analog shunt loudspeakers. The theoretical model was established based on the electro-mechanical–acoustic analogy method and parallel impedance method. Numerical simulations and experimental studies were performed to verify the proposed model. The results demonstrate that the proposed absorber can achieve excellent low-frequency sound absorption capability by designing only a few digital filter parameters, while simultaneously enhancing the stability and accuracy of the system. This study presents a promising innovative method for low-frequency noise control at sub-wavelength scales, providing a space-efficient solution. Full article

Lithium-ion batteries form the backbone of the recent transition to electric vehicles (EVs). Due to limited capacities, costly replacements, and short lifetimes, proper control and management systems are essential for developing modern battery-powered EV systems. Brushless direct current (BLDC) motors have gained popularity in traction and industrial drive applications due to their high efficiency and long lifespan. The speed controller for the BLDC motor is a critical element in defining the system’s overall response and performance. Therefore, this paper presents a non-integer fractional-order control scheme to enhance a hybridized speed controller for BLDC motors. Unlike existing integer- and non-integer-based controllers in the literature, the new modified controller is a hybrid structure that combines the three control schemes. The proposed control is constructed using the hybrid proportional-tilt-fractional order Integrator-derivative with filter (PTFOIDN) controller. The proposed PTFOIDN controller inherently incorporates the merits of FOPI, TID, and FOPID control structures and branches within a single, hybridized structure. The proposed PTFOIDN controller features eight tunable parameters, allowing for more flexible design possibilities. Furthermore, a practical design methodology using a recent Marine Predators Algorithm (MPA) is proposed in this paper to determine the optimum set of control parameters simultaneously. Different drive cycles, comparative analysis, and operating scenarios are presented in the paper to validate the effectiveness of the new proposed PTFOID controller and MPA-based control design. Full article

This work focuses on the magneto-optical behavior of one-dimensional ternary photonic crystals that incorporate extrinsically magnetized GaAs as a functional layer. In this context, we investigate the effect of an applied transverse magnetic field on the optical response and photonic band gap characteristics of the proposed structure. The transfer matrix method is utilized to analyze the optical response of the ternary structure. The ternary photonic crystal with extrinsically magnetized GaAs exhibits strong magnetic tunability. The photonic band gap shifts from 0.32 THz to 0.38 THz under an applied external magnetic field up to 0.75 T with 100% band gap modulation. The polarization mode also shifts within the range of 0.32–0.36/0.38 THz due to the anisotropic response of the magnetized GaAs. These results confirm the effectiveness of extrinsic magnetization for compact, dynamically tunable photonic devices. The proposed configuration thus provides an effective framework for developing multichannel and broadband transmission filters that can be adjusted in the terahertz domain. Full article

This paper introduces a theoretical framework for designing and tuning band-pass filters with a highly extended periodicity using cascaded Mach-Zehnder Interferometer (MZI) networks. We show that a filter centered at frequency f₀ with a bandwidth of FSR₀ and an arbitrarily large free spectral range (FSR) can be built with a minimal number of MZIs by using stages with FSRs that are prime multiples of FSR₀. Due to the inherent multi-spectral transparency of materials, this design ensures that only a single narrow passband is transparent. We derive the total power transmission for such a cascaded system and show that the filter’s overall periodicity is the product of the individual MZI transfer functions. Furthermore, we deduce the linear relationship between the applied differential voltage and the resulting frequency shift, offering a precise method for continuous spectral tuning without altering the filter’s intrinsic FSR. We propose a new, simplified electronic circuit that uses a single input current and series impedances for continuous resonant peak tuning and analyze the feasibility of such a design. This circuit improves practical implementation and allows for compensation of fabrication errors. This work offers crucial analytical tools and insights for developing advanced reconfigurable photonic integrated filters, essential for future optical communication and sensing systems. Full article

This research presents a novel dual-mode filter design that offers significant advantages in terms of frequency agility and miniaturization compared to conventional fixed multi-resonator filters. The design and implementation of a compact tunable bandpass filter are presented. The basic design structure is based on a slotted non-degenerate dual-mode microstrip square patch. The slots are etched symmetrically, which makes the slotted dual-mode square patch equivalent to a two-coupled-resonator filter. The asymmetrical feed lines enable the excitation of dual resonant modes. The patch length, slot size, and dielectric material properties primarily determine the filter’s center frequency and bandwidth. Tunability is achieved by loading the slotted square patch with reversed bias varactor diodes located at the square patch corners, allowing electronic control of the filter center frequency. The design utilizes RT/Duroid 6010.2 laminates with a dielectric constant of 10.2 and a thickness of 0.635 mm. A bias tee at one of the filter ports is used to provide reverse bias to varactor diodes. Simulations and experimental results demonstrate tunable characteristics. Among the attractive features of the proposed design, good levels of insertion loss and impedance matching are noticed in the entire tunable band. The advantages of the proposed design make it well-suited for modern wireless technology applications in communication, radar, and satellite systems. Full article