Switchable Filter Research Articles

Balanced switchable bandpass filter with differential‐mode reflectionless characteristics

AbstractThis paper presents a balanced switchable bandpass filter (SBPF) with differential‐mode (DM) reflectionless characteristics in the on‐state. The proposed SBPF consists primarily of dual‐mode resonators loaded with p‐type–intrinsic–n‐type diodes, absorptive stubs, and common‐mode suppression (CMS) networks. The resonance conditions of the diode‐loaded dual‐mode resonator in both on/off states, as well as the design principles of the balanced SBPF's, are analyzed and derived. To verify the design concept, a balanced SBPF prototype with a center frequency of 2.6 GHz was designed and manufactured. The measured results show that the proposed SBPF exhibits low DM insertion loss and a wide DM reflectionless bandwidth in the on‐state, high DM isolation in the off‐state, and effective CMS.

Highly Permeable, Electrically Switchable Filter for Multidimensional Sorting of Suspended Particles

The creation of highly specific particle systems in the nano- and micrometer size range is a challenging task. The demand for particle systems with narrowly distributed properties is increasing in many applications, especially for use in high-tech products. Conventional separation techniques often reach their limits in the micrometer size range or become (labor-)intensive, which makes them economically or ecologically unsustainable. In addition, sorting based on several properties is rarely feasible in just one separator. Dielectrophoretic processes can be a viable option for complex sorting tasks like this, given their ability to address several particle properties and their high degree of selectivity. In this paper, we summarize the progress of a project in which the capability of dielectrophoretic methods for multidimensional sorting of microparticles was investigated. We were able to develop an operation mode for multidimensional sorting of microparticles using dielectrophoresis as well as a scalable electrically switchable filter. This creates a basis for high-throughput and multi-target sorting of technical microparticles using dielectrophoretic processes.

(Keynote) Soft Wet Iontronic Devices with Affinity to Biosystems

A super-aging society, frequent natural disasters, and coronavirus pandemics are accelerating the transition to a highly efficient DX society. There is also an urgent need to build a DX medical system with online integrated management of self-care (diagnosis and treatment performed by each individual) and self-medication. One of the technological cornerstones of such self-medicine lies in the innovation in "bioaffinity" of wearable and implantable devices that connect between medical systems and living body.Over the past decades, device engineering has pursued bioaffinity through the process of miniaturization and slimming, and recently there is a growing trend to incorporate soft and wet materials with a similar softness to biological tissues in device applications. Furthermore, in addition to these progress in "material affinity", it becomes imperative to drive forward the development of ion-driven molecular delivery and stimulation systems with "affinity to biosystems" to realize truly biocompatible self-care devices.So far, we have studied the materials and technologies for the “Electron ↔ Ion ↔ Molecule ↔ Flow” energy/information multi-conversion, and developed the following iontronic systems to generate ion-flow (1, 2) and drive molecular transports (3, 4).(1) Electron/Ion conversion electrode: Ultra-high capacity electrode materials generate ion current "without electrolysis", ensuring secure and precise stimulation, even in close proximity to living tissues.(2) Molecular/Ion conversion electrode: Converting molecular information/energy into ion current using enzymes as electrocatalysts, enabling devices to be independent of external power sources and linking sensing and stimulation functions.(3) Ion-driven hydrogel pump and switch filter: Precise reversible control of electroosmotic flow electrically (with the ionic flow) using charge-fixed hydrogels. The ion polarity of the electric double layer formed on the micropore wall of the filter is controlled to reversibly switch the direction of electroosmotic flow.(4) Permeable microneedles: Porous microneedle array that provides minimally invasive molecular delivery to pinpoints in biological tissues under control by electroosmotic flow.Utilizing these iontronic systems, we have produced a few self-care devices. Organic intracranial and nerve cuff electrodes composed of hydrogel are is on the verge of being launched [1, 2]. The intracranial electrode has already been employed in epilepsy surgery (the first case of the clinical trial). The prototypes of the bio-powered skin patches [3-5] have shown effects of wound healing and pain relieve. The ion-driven hydrogel pumps and porous microneedles are our important minimally low-invasive interfacing tools [6-9], with which electroosmotic flow can be controlled for drug and vaccine administrations. In this presentation, I will explain these our recent progress in ion-driven self-care devices, and discuss our future plans.

Switchable anisotropic diffraction mode filter based on fork-like liquid crystal gratings

The interaction of liquid crystal (LC) fork-like gratings (FLGs) with a Laguerre–Gaussian beam of the TEM00 mode is described. It is experimentally shown that when the direction of the light polarization vector differs from the direction of the LC eigenvectors, the medium behaves as an FLG with a controlled modulation depth, and in the opposite case, it is isotropic and homogeneous. Distributions of the intensities of the longitudinal section of the beam in the infinitely far field are given depending on the FLG rotation angle in the plane perpendicular to the direction of beam propagation. It is shown that the LC FLG functions as a switchable anisotropic diffraction mode filter.

Adaptive nonlinear filtering algorithms for removal of non-stationary noise in electronystagmographic signals

Non-stationary physiological noise poses significant difficulties due to its time-varying and previously unknown characteristics. When processing electronystagmographic signals, linear filtering can distort diagnostically significant rapid changes caused by saccadic eye movements. In such cases, nonlinear filters based on robust estimators are more appropriate, whereas linear filtering effectively reduces white noise in parts of a signal with linear behaviour. Therefore, an adaptive signal processing approach that varies in nonlinearity from highly nonlinear robust estimation to linear averaging and combines their benefits appears promising. We have proposed a low-complexity adaptive method for switching filter sets and relevant filter parameter settings based on the estimated noise level and local signal behaviour. This method does not require time for filter parameter modification and does not need prior information on the signal model and noise variance. Based on this method, we have designed adaptive nonlinear filtering algorithms to exploit the advantages of both the nonlinear robust and linear averaging estimators. We have evaluated the filtering quality statistically using the minimum mean square error criteria and the maximum signal-to-noise ratio for a model signal with different levels of additive Gaussian noise. The proposed real-time adaptive filtering algorithms demonstrate a significant efficiency improvement compared to the commonly used filters. The proposed adaptive myriad algorithm achieves the highest efficiency by adjusting a sample myriad linearity parameter depending on the local estimate of a signal scale and changing the sliding window length and the coefficient affecting the linearity parameter.

Balanced Switchable Bandpass Filter With All‐Port Reflectionless and Common‐Mode Suppression Characteristics

ABSTRACTA novel balanced switchable bandpass filter with all‐port reflectionless characteristics is proposed in this paper. The balanced switchable bandpass filter comprises a balanced switchable filtering section with bandpass response and two absorptive networks. The absorptive network proposed in this paper adopts only one structure to achieve both differential‐ and common‐mode reflectionless characteristics. The proposed switchable resonators in the filtering section and the proposed absorption networks excited under even‐ and odd‐modes are analyzed in detail. For the purpose of verification, a prototype is manufactured based on the simulated results, and it has a good consistency. The experimental results exhibit that the proposed balanced bandpass filter exhibits a differential‐mode bandpass filtering function and all‐port reflectionless performance in the ON‐state, differential‐mode isolation function, common‐mode suppression, and reflectionless behavior in the OFF‐state, which verifies the feasibility of the design theory.

Adaptive Jamming Mitigation in Single-Antenna Receivers With Spectral Analysis and Switchable Filtering

Adaptive Jamming Mitigation in Single-Antenna Receivers With Spectral Analysis and Switchable Filtering

Switchable SAW Resonators and Ladder Filters Composed of Interdigitated Combs.

This work presents the development of switchable surface acoustic wave (SAW) resonators fabricated on a LiNbO3 substrate, which uses the electrical Bragg bandgap concept to control the resonance frequency. The modification of the electrical condition of electrode arrays shifts their bandgap center frequency, which in turn changes the effective cavity length and resonance frequency of the resonator. This method uses the electrodes already present in SAW devices, thus reducing the complexity of potentially tunable SAW components. In this article, the electrodes that make up the cavity mirrors are connected into interdigitated comb pairs (IDCPs), reducing the necessary number of switches for operation. Finite-element method (FEM) simulations are used to analyze resonator operation and design difficulties are discussed. Frozen (with no possibility of switching) and switchable versions of a chosen resonator structure are fabricated to experimentally showcase resonator operation. It is found that it is possible to design switchable SAW resonators, which require a single switch and present a relative frequency jump of around 2.3%. Finally, frozen single-cell and four-cell ladder filters are fabricated as a proof of concept of a switchable SAW filter.

Eight-wavelength-switchable single-frequency fiber laser with scattering-enhanced fiber-based wavelength self-adaptive linewidth compression.

We demonstrate an eight-wavelength-switchable single-frequency (SF) ultra-narrow linewidth erbium-doped fiber laser (EDFL). A switchable polarization-dependent eight-channel filter (S-PDECF), fabricated using femtosecond laser direct-writing technology, determines the eight wavelengths of the laser output, with four channels concentrated near 1530 nm and the other four near 1550 nm. A dual-coupler ring-based compound-cavity filter is utilized to achieve single-longitudinal-mode selection for the EDFL. The introduction of a femtosecond laser direct-written scattering-enhanced fiber (SEF) effectively narrows the laser linewidth, enabling ultra-narrow linewidth outputs lasing at all eight wavelengths, and the wavelength self-adaptive linewidth compression of the SEF is verified for the first time. Furthermore, the incorporation of SEF significantly enhances the overall performance of the EDFL. The eight switchable single-wavelength laser outputs all exhibit exceptional characteristics, including spectral wavelength fluctuations of ≤0.011 nm, spectral peak power fluctuations of ≤0.54 dB, optical signal-to-noise ratios of ≥71 dB, linewidths of ≤248 Hz, output power fluctuations of ≤0.252 dB over a 10-min measurement period, and relative intensity noise of ≤-150.17 dB/Hz @≥ 3 MHz.

Minimum-energy switching geometric filter on lie groups for differential-drive wheeled mobile robots

Accurate state estimation plays a critical role in various applications, such as tracking, regulation, and fault detection in robotic and mechanical systems. Typically, the Kalman–Bucy filter is used as a linear state observer for this purpose. However, real-world robots often exhibit complex behavior, characterized by a combination of dynamics, making it essential to employ hybrid filters. In this context, the Switching Kalman filter stands out as a well-established solution. In this article we aim to generalize the Brownian-Markov Stochastic Model, a hybrid dynamic model for differential-drive wheeled mobile robots, to the case of a mobile robot whose center of mass is not aligned to the wheels axle middle point, and to design a geometric hybrid state estimator by exploiting the Lie groups theory. The Brownian-Markov Stochastic Model features two modes: “grip” and “slip”. These modes correspond to ideal grip and lateral slippage, with transitions governed by a state-dependent Markov chain. To validate the proposed switching filter, we conduct MATLAB® simulations of the robot’s motion in a scenario prone to lateral grip loss, comparing the state estimates produced by the switching geometric filter with those obtained using the switching Kalman filter.

Design of high selectivity tunable bandpass filter with switchable single‐/dual‐band responses

AbstractThis article proposes a switchable filter with four operating states, namely dual‐band mode, lower band mode, upper band mode, and all‐stop mode. The transition between these states is achieved by using positive intrinsic negative diodes, while the center frequency tuning is done by using varactors. In order to verify the design concept, a prototype has been fabricated on an F4BME substrate with a dielectric constant of 2.25 and a thickness of 1 mm, and the measured results were in agreement with the simulations. Notably, the dual‐band mode yields four transmission zeros (TZs), while the single‐band mode produces two TZs. The final circuit size of the designed filter is 0.18 × 0.14 λg, making it ideally suited for reconfigurable multi‐band communication systems.

Floquet-engineered valley topotronics in Kekulé-Y bond textured graphene superlattice

The exquisite distortion in a Kekulé -Y (Kek-Y) superlattice merges the two inequivalent Dirac cones (from the K- and the K′- points) into the highest symmetric Γ-point in the hexagonal Brillouin zone. Here, we report that UV circularly polarized light not only opens up a topological gap at the Γ-point, but also lifts the valley degeneracy at that point. Endowed with Floquet dynamics and by devising a scheme of high-frequency approximation, we propose that the left/right-handedness in polarized light offers the possibility to realize valley-selective circular dichroism in a Kek-Y-shaped graphene superlattice. In addition, the non-vanishing Berry curvature and enumeration of the valley-resolved Chern number CK/CK′=+1/−1 enable us to assign two pseudospin flavors (up/down) with the two valleys. Thereby, the above observations confirm the topological transition, suggesting the ease of realizing the valley quantum anomalous Hall state within the photon-dressed Kek-Y. These findings further manifest a non-zero optical valley polarization that is maximal at the Γ-point. Our paper thus proposes an optically switchable topological valley filter, which is desired in the evolving landscape of valleytronics.

Dual-track spectrometer design for 1D gas-phase Raman spectroscopy.

In this study, a new design for a 1D gas-phase Raman spectrometer is presented, utilizing two dedicated tracks to image different properties of the measured signal onto a single charge-coupled device (CCD) chip. Two possible configurations are shown: a polarization-separation configuration, which separates the detected Raman signal into s- and p-polarized shares; and a dual-resolution configuration, which captures all process-relevant species in a range of approximately 515-4650 cm-1 on one track and the highly resolved nitrogen spectrum on the other. This new spectrometer design offers several advantages when compared to traditional polarization-separation/dual-resolution systems, which often use switchable filters or two different spectrometers in tandem to achieve comparable measurements. Employing only one camera eliminates signal drift and minimizes calibration as well as spatial/spectral mapping issues. To validate instrument performance, the detection was paired with a continuous wave (CW) excitation system and used to measure in two generic but diagnostically challenging flow scenarios: flow near a heated surface, where thermal radiation is significant addressed by the polarization-separation configuration of the spectrometer and a channel flow at moderate temperatures in confined space, where the dual-resolution configuration of the spectrometer was employed. The results for both configurations and experiments showcase the instrument's ability to effectively suppress background radiation (polarization-separation) or measure local gas-phase temperatures with higher accuracy (dual-resolution) and are complemented with resolution measurements yielding a maximum spatial resolution of 21.9 lp/mm along the 1D probe volume.

Phase change material metasurface loading enables an ultrafast all-optically switchable, compact, narrowband freespace optical filter

Active metasurfaces leveraging phase change materials (PCMs) remain a subject of intense investigation, owing to their inherent tunable properties and successful integration into integrated photonics. By harnessing the ultra-compact form factor of optical metasurfaces, further advancements in switching speeds and reduction in switching energies have the potential to revolutionize applications in free space optical communication, optical signal processing, neuromorphic photonics, quantum photonics, and compact LiDAR. In this context, an ultrafast all-optically switchable narrowband spectral filter employing a distributed Bragg reflector cavity loaded with a PCM-metasurface is proposed. The work involves a comprehensive numerical exploration of its optical properties, encompassing design optimization and anticipating limits in switching speeds and energy requirements. Specifically, focusing on a GST225 metasurface operating in the shortwave-infrared spectrum, the numerical investigations reveal the potential to achieve transmission contrast levels as high as 24 dB, accompanied by Q-factors up to a thousand and less than 1 dB insertion loss. This performance notably outperforms recently reported free-standing PCM metasurfaces and cavities loaded with unstructured PCM thin films. Furthermore, the study predicts full-cycle reconfigurability (transitioning from amorphous to crystalline states and vice versa) with anticipated switching speeds of 91 & 200 MHz and switching fluence of 0.655 & 0.616 mJ/cm2 per cycle for the RESET and SET processes respectively. This investigation holds promise for advancing the state-of-the-art performance of PCM-based metasurfaces.

31‐2: Switchable View Control using a Vertically Aligned Polarizer and Polarization Control

Combining a vertically aligned polarizer and a liquid crystal cell, a switchable view control filter is implemented, that on demand, changes the transmission for designated view angle areas between a high transmission and low transmission state, referred to as private and public modes of operation. The feasibility of the switchable view control concept is confirmed via simulations and measurements.

Optoelectronically controlled spin-valley filter and nonlocal switch based on an asymmetrical silicene magnetic superconducting heterostructure

We investigate the effects of the circularly polarized light (CPL) and the electric field (EF) on the nonlocal transport in a silicene-based antiferromagnet/superconductor/ferromagnet (AF/S/F) asymmetrical junction. For case I (II), the CPL and the EF are applied simultaneously in the antiferromagnetic (ferromagnetic) region, whereas in the ferromagnetic (antiferromagnetic) region, only a constant EF is considered. The spin-valley-resolved conductance can be turned on or off by adjusting the CPL or the EF. The AF/S/F junction can be manipulated as a spin-locked valley filter for case I, while for case II, it can be used not only as a valley-locked spin filter but also as a nonlocal switch between two pure nonlocal processes. Such interesting nonlocal switch effect can be effectively controlled by reversing the direction of the incident energy axis, the handedness of the CPL, or the direction of the EF. These findings may open an avenue to the design and manufacture of the spintronic and valleytronic devices based on the asymmetrical silicene magnetic superconducting heterostructure.

Using Active Filter Controlled by Imperialist Competitive Algorithm ICA for Harmonic Mitigation in Grid-Connected PV Systems

Solar energy has been gaining momentum recently, with a focus on maximizing its investment potential due to its reputation as the most sustainable and efficient energy source. This shift towards solar power could potentially reduce the reliance on oil-based fuels in the future. As a result of the integration of photovoltaic (PV) energy sources into the grid, the reliability of power distribution and maintaining its quality in these systems has become increasingly important. The presence of non-linear loads in these grids causes distortion of both voltage and current waves on the grid side, so it is necessary to implement effective reduction techniques to reduce the distortions in these waves. The research contribution is TO introduce the integration of an active filter on the dc side of grid-connected PV systems, along with a control circuit for the filter switches. The control switches were operated using a Sinusoidal Pulse Width Modulation (SPWM) control scheme, while the controller parameters were tuned using the Imperialist Competitive Algorithm (ICA). The proposed system was simulated in the MATLAB/Simulink environment with variations in solar radiation and temperature. The simulation results demonstrated a reduction in the total harmonic distortion factor (THD) for voltage and current waveforms on the grid side, which are within the permissible limits. This confirms the effectiveness of the proposed filter and the efficiency of the control strategy and algorithm for parameter adjustment.

Frequency tunable magnetostatic wave filters with zero static power magnetic biasing circuitry

A single tunable filter simplifies complexity, reduces insertion loss, and minimizes size compared to frequency switchable filter banks commonly used for radio frequency (RF) band selection. Magnetostatic wave (MSW) filters stand out for their wide, continuous frequency tuning and high-quality factor. However, MSW filters employing electromagnets for tuning consume excessive power and space, unsuitable for consumer wireless applications. Here, we demonstrate miniature and high selectivity MSW tunable filters with zero static power consumption, occupying less than 2 cc. The center frequency is continuously tunable from 3.4 GHz to 11.1 GHz via current pulses of sub-millisecond duration applied to a small and nonvolatile magnetic bias assembly. This assembly is limited in the area over which it can achieve a large and uniform magnetic field, necessitating filters realized from small resonant cavities micromachined in thin films of Yttrium Iron Garnet. Filter insertion loss of 3.2 dB to 5.1 dB and out-of-band third order input intercept point greater than 41 dBm are achieved. The filter’s broad frequency range, compact size, low insertion loss, high out-of-band linearity, and zero static power consumption are essential for protecting RF transceivers from interference, thus facilitating their use in mobile applications like IoT and 6 G networks.

UV-NDVI for real-time crop health monitoring in vertical farms

This study aims to develop a plant health monitoring system suitable for vertical farms. It began by creating a multispectral LED with UVA and NIR light sources and an IoT device capable of controlling the LED spectrum. The IoT device integrates a camera with switchable filters and RGB CMOS sensor to simultaneously calculate SI-NDVI (single-image normalized difference vegetation index) and UV-NDVI (UV induce red chlorophyll fluorescence normalized difference vegetation index).A lettuce cultivation experiment was conducted on a planting shelf in a controlled environmental room, with two cultivation planters containing the same nutrient solution and red lettuce variety. SI-NDVI and UV-NDVI were calculated every three hours to compare differences. Results showed that both UV-NDVI and SI-NDVI trends were similar in monitoring lettuce growth. However, UV-NDVI was more sensitive to plant health than SI-NDVI. By inducing drought stress, the UV-NDVI indicator was able to detect water deficiency anomalies earlier than visual observation.

Tri-channel independent switching terahertz filter based on metal-graphene hybrid coding metasurface

Terahertz (THz) filters are the core devices for practical application in THz communication technology. Recently, design of multi-channel filters with high modulation rates remains to be a challenge. In this paper, a three channels switchable THz filter based on metal-graphene hybrid metasurface is proposed. The unit cell is consisted of "n"-shaped and "u"-shaped split-ring resonators (SRRs) with different sizes, and the graphene bar is embedded at the gap of two SRRs. The four bandpass modes with single transparency windows, double two transparency windows, and three transparency windows can be freely switched by applying voltage to the left/right electrodes of the filters. Its central frequencies of transparency windows are located at 0.80 THz with modulation depth up to 49%, 1.14 THz (constant transparency windows), and 1.58 THz with modulation depth up to 68%, respectively. In addition, an equivalent circuit model is proposed to demonstrate the control mechanism. This research result not only provides a new method for the design of reconfigurable multifunctional THz modulation devices, but also give theoretical model to promote the development of multi-channel filter technology in THz communication technology.