Lower Cutoff Frequency Research Articles

RGB camera-based simultaneous measurements of percutaneous arterial oxygen saturation, tissue oxygen saturation, pulse rate, and respiratory rate.

We propose a method to perform simultaneous measurements of percutaneous arterial oxygen saturation (SpO 2), tissue oxygen saturation (StO 2), pulse rate (PR), and respiratory rate (RR) in real-time, using a digital red–green–blue (RGB) camera. Concentrations of oxygenated hemoglobin (C HbO), deoxygenated hemoglobin (C HbR), total hemoglobin (C HbT), and StO 2 were estimated from videos of the human face using a method based on a tissue-like light transport model of the skin. The photoplethysmogram (PPG) signals are extracted from the temporal fluctuations in C HbO, C HbR, and C HbT using a finite impulse response (FIR) filter (low and high cut-off frequencies of 0.7 and 3 Hz, respectively). The PR is calculated from the PPG signal for C HbT. The ratio of pulse wave amplitude for C HbO and that for C HbR are associated with the reference value of SpO 2 measured by a commercially available pulse oximeter, which provides an empirical formula to estimate SpO 2 from videos. The respiration-dependent oscillation in C HbT was extracted from another FIR filter (low and high cut-off frequencies of 0.05 and 0.5 Hz, respectively) and used to calculate the RR. In vivo experiments with human volunteers while varying the fraction of inspired oxygen were performed to evaluate the comparability of the proposed method with commercially available devices. The Bland–Altman analysis showed that the mean bias for PR, RR, SpO 2, and StO 2 were -1.4 (bpm), -1.2(rpm), 0.5 (%), and -3.0 (%), respectively. The precisions for PR, RR, Sp O 2, and StO 2 were ±3.1 (bpm), ±3.5 (rpm), ±4.3 (%), and ±4.8 (%), respectively. The resulting precision and RMSE for StO 2 were pretty close to the clinical accuracy requirement. The accuracy of the RR is considered a little less accurate than clinical requirements. This is the first demonstration of a low-cost RGB camera-based method for contactless simultaneous measurements of the heart rate, percutaneous arterial oxygen saturation, and tissue oxygen saturation in real-time.

Electrochemical and biological performance of hierarchical platinum-iridium electrodes structured by a femtosecond laser

Neural electrode interfaces are essential to the stimulation safety and recording quality of various bioelectronic therapies. The recently proposed hierarchical platinum-iridium (Pt-Ir) electrodes produced by femtosecond lasers have exhibited superior electrochemical performance in vitro, but their in vivo performance is still unclear. In this study, we explored the electrochemical performance, biological response, and tissue adhesion of hierarchical Pt-Ir electrodes by implantation in adult rat brains for 1, 8, and 16 weeks. Regular smooth Pt-Ir electrodes were used as a control. The results showed that the electrochemical performance of both electrodes decreased and leveled off during implantation. However, after 16 weeks, the charge storage capacity of hierarchical electrodes stabilized at ~16.8 mC/cm2, which was 15 times that of the smooth control electrodes (1.1 mC/cm2). Moreover, the highly structured electrodes had lower impedance amplitude and cutoff frequency values. The similar histological response to smooth electrodes indicated good biocompatibility of the hierarchically structured Pt-Ir electrodes. Given their superior in vivo performance, the femtosecond laser-treated Pt-Ir electrode showed great potential for neuromodulation applications.

Perencanaan Rancang Bangun Microstrip Band Pass Filter dengan Struktur Tapped Input Hairpin pada Aplikasi Jaringan Mid-band 5G Telkomsel

Microstrip filter is a type of Radio Frequency (RF) filter that uses a thin electrical conductor separated from the ground plane by using a dielectric called the substrate. Microstrip filters are generally printed on Printed Circuit Boards or PCBs where high-frequency signals are directed from one part of the system to another with high efficiency. There are several types that can be applied to the operation of microstrip filters, one of which is a band pass filter. Band pass filter is a filter that can pass a signal with a certain frequency that is limited by a low cut-off frequency and a high cut-off frequency, and is able to dampen signals that are below the cut-off frequency and above the high cut-off frequency. There are several types of resonator designs that can be used for reference in the manufacture of microstrip filters, such as tapped line input hairpin filters, stub loaded filters, stepped impedance filters, and combline filters. By using the reference form of the tapped line input hairpin, this journal is intended for planning the manufacture of microstrip filters in the application of Telkomsel's 5G technology.

Design of Filtering Magic-T with Wideband and Wide Stopband Based on HMSIW and Spoof Surface Plasmon Polaritons

A novel filtering magic-T (FMT) with a compact size, a broad bandwidth, and a wide stopband rejection based on the dielectric-covered L-shaped groove (DCLSG) half-mode substrate integrated waveguide and the spoof surface plasmon polariton (HMSIW-SSPP) structure is proposed for the first time. A HMSIW magic-T (HMT) based on dual-layer substrates is first designed. Then, we construct the proposed FMT by periodically etching the subwavelength DCLSG SSPP structure into the HMT. The proposed FMT achieves a bandpass filtering response and a nearly 50% reduction of longitudinal dimension attributed to the bandpass characteristics and strong slow-wave property of the DCLSG HMSIW-SSPP structure. In addition, beneficial from the regulable cut-off frequencies of the DCLSG HMSIW-SSPP structure, the proposed FMT provides a wide impedance bandwidth and independently adjustable lower and upper cut-off frequencies of the passband. Finally, a prototype of the proposed FMT is fabricated to validate this design idea. The measured results illustrate that the FMT has a 3-dB fractional bandwidth of 40.23% and a 20-dB stopband rejection up to 2.12 f0 (f0: center frequency of the passband).

Glassy thermal conductivity in Cs3Bi2I6Cl3 single crystal

As the periodic atomic arrangement of a crystal is made to a disorder or glassy-amorphous system by destroying the long-range order, lattice thermal conductivity, κL, decreases, and its fundamental characteristics changes. The realization of ultralow and unusual glass-like κL in a crystalline material is challenging but crucial to many applications like thermoelectrics and thermal barrier coatings. Herein, we demonstrate an ultralow (~0.20 W/m·K at room temperature) and glass-like temperature dependence (2–400 K) of κL in a single crystal of layered halide perovskite, Cs3Bi2I6Cl3. Acoustic phonons with low cut-off frequency (20 cm−1) are responsible for the low sound velocity in Cs3Bi2I6Cl3 and make the structure elastically soft. While a strong anharmonicity originates from the low energy and localized rattling-like vibration of Cs atoms, synchrotron X-ray pair-distribution function evidence a local structural distortion in the Bi-halide octahedra and Cl vacancy. The hierarchical chemical bonding and soft vibrations from selective sublattice leading to low κL is intriguing from lattice dynamical perspective as well as have potential applications.

Ultrahigh-Amplitude Isolated Attosecond Pulses Generated in the Transmission Regime from Ultrathin Foil

A coherent-synchrotron-emission regime of forward high-order harmonics generation (HHG) is proposed for the emission of an isolated unipolar half-cycle attosecond pulse by a three-color laser pulse impinging on ultrathin foil. A theoretical model is proposed for the electron nanobunching mechanism and the forward radiation, which is consistent with the numerical-simulation results. As the forward HHG does not need to penetrate from the front to the rear side of the target, the spectrum of the forward HHG has no low-frequency cutoff. The robustness of this regime is verified with different laser and foil plasma conditions as well as the two-dimensional effects. The robustness is also checked with similarity theory, which confirms that isolated attosecond pulses can be efficiently generated when the plasma density and the laser amplitude change simultaneously such that their ratio remains unchanged.

Compact Dual-Polarized Filtenna With Steep Roll-Off Rate for Base Stations

This letter presents a dual-polarized, band-pass filtering antenna, or “filtenna” with a steep roll-off rate and a compact size. To simultaneously support multiple communication standards in a shared aperture, base station antenna arrays need to operate in multiple closely-spaced frequency bands. However, each filtenna has a limited space in the aperture-shared array; therefore, it is challenging to achieve a high roll-off rate. To resolve this problem, we proposed a filtenna that consists of four stacked X-shaped patches, of which the second from the bottom is the driven patch and the rest are parasitic ones. These closely coupled parasitic patches switch rapidly from resonance to antiresonance; however, their radiations change because they together cancel one another and create a very steep roll-off rate. The aperture dimension of the proposed antenna is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.2 \, \lambda _{0} \times 0.2 \, \lambda _{0} \times 0.14 \, \lambda _{0}$</tex-math></inline-formula> , where <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\lambda _{0}$</tex-math></inline-formula> is the wavelength in free space at the center frequency. The measurement results demonstrate a very steep roll-off rate up to 1795 dBi/GHz at the lower cutoff frequency of 1.8 GHz. The measured average gain was 8 dBi over the operating frequency band of 1.805–1.88 GHz, which makes the proposed filtenna a good candidate for multiband and multistandard base stations.

Slow Wave Gap Waveguide With Bandpass Filtering Functionality

Gap waveguide (GW) technology, taking advantage of contactless electromagnetic band-gap (EBG) structures, solves the contact issue of conventional rectangular waveguides and provides a reliable method for packaging with planar circuits. Herein, a slow wave GW (SW-GW) structure with bandpass filtering functionality is presented. Utilizing the low-frequency cutoff characteristic of the GW and band-stop effect of the quasi-periodic transverse corrugations inside the GW, the lower and upper stopbands of the SW-GW can be easily achieved and reconfigured for different bandwidth requirements. The relationship between the dispersion diagram and the filtering characteristics, including the pass and stop bandwidths and group delay (GD), is studied to provide a simple but effective design guideline. The presented SW-GW reduces the design and implementation difficulties of conventional filters, especially wideband filters. A prototype operating at 24–30 GHz is designed and manufactured to validate the idea, and a good agreement is achieved between the measurement and simulation results.

Metamaterial split-ring resonators applied as reduced-size four-port antenna array for MIMO applications

A reduced-size four-port antenna array with highly electromagnetic isolation based on a metamaterial structure is presented. The radiator antenna unit is created using the split ring resonator (SRR) arrangement, which has been widely demonstrated to perform as metamaterial. The metamaterial comportment allows increasing the slow-wave factor on the structure, and as a result, the array size is 42×42mm2, where each radiator presents a 52% length reduction compared to a conventional disc monopole with lower cutoff frequency of 2.5 GHz. The separation among elements is very small, achieving values of 0.045λ at the resonance; however, despite the proximity among elements, the electromagnetic isolation reaches values around 30 dB all over the working band. The antenna has a wide bandwidth, going from 2.5 GHz to almost 4 GHz. The array performs a very low Envelope Correlation Coefficient (ECC), achieving levels lower than 0.035 and a steady Total Active Reflection Coefficient (TARC), obtaining a system bandwidth of 1.38 GHz for a TARC ≤−10dB, resulting a suitable structure for Multiple-Input Multiple-Output (MIMO) applications.

An Efficient Hybrid Methodology for Local Activation Waves Detection under Complex Fractionated Atrial Electrograms of Atrial Fibrillation.

Local activation waves (LAWs) detection in complex fractionated atrial electrograms (CFAEs) during catheter ablation (CA) of atrial fibrillation (AF), the commonest cardiac arrhythmia, is a complicated task due to their extreme variability and heterogeneity in amplitude and morphology. There are few published works on reliable LAWs detectors, which are efficient for regular or low fractionated bipolar electrograms (EGMs) but lack satisfactory results when CFAEs are analyzed. The aim of the present work is the development of a novel optimized method for LAWs detection in CFAEs in order to assist cardiac mapping and catheter ablation (CA) guidance. The database consists of 119 bipolar EGMs classified by AF types according to Wells’ classification. The proposed method introduces an alternative Botteron’s preprocessing technique targeting the slow and small-ampitude activations. The lower band-pass filter cut-off frequency is modified to 20 Hz, and a hyperbolic tangent function is applied over CFAEs. Detection is firstly performed through an amplitude-based threshold and an escalating cycle-length (CL) analysis. Activation time is calculated at each LAW’s barycenter. Analysis is applied in five-second overlapping segments. LAWs were manually annotated by two experts and compared with algorithm-annotated LAWs. AF types I and II showed accuracy and sensitivity. AF type III showed accuracy and sensitivity. The results of this study highlight the efficiency of the developed method in precisely detecting LAWs in CFAEs. Hence, it could be implemented on real-time mapping devices and used during CA, providing robust detection results regardless of the fractionation degree of the analyzed recordings.

Viscoelastic Scaling Regimes for Marginally Rigid Fractal Spring Networks.

A family of marginally rigid (isostatic) spring networks with fractal structure up to a controllable length was devised, and the viscoelastic spectra G^{*}(ω) calculated. Two nontrivial scaling regimes were observed, (i)G^{'}≈G^{''}∝ω^{Δ} at low frequencies, consistent with Δ=1/2, and (ii)G^{'}∝G^{''}∝ω^{Δ^{'}} for intermediate frequencies corresponding to fractal structure, consistent with a theoretical prediction Δ^{'}=(ln3-ln2)/(ln3+ln2). The crossover between these two regimes occurred at lower frequencies for larger fractals in a manner suggesting diffusivelike dispersion. Solid gels generated by introducing internal stresses exhibited similar behavior above a low-frequency cutoff, indicating the relevance of these findings to real-world applications.

Numerical model & design of wideband band reject filter with closed loop rectangular resonator

ABSTRACT Numerical model of a wideband band reject filter using closed rectangular loop resonator is presented using transmission lines. The prototype design of wide band reject filter centred at 3 GHz with lower cut-off frequency of 2 GHz and upper cut-off frequency of 4 GHz is fabricate from the optimal values obtained from the numeric model on a substrate (FR4) with a dielectric constant of 4.3, loss tangent of 0.02–0.03 and substrate height of 1.6 mm. For bidirectional operations, the length-to-width ratio of filter is 2:1. The impedance of the transmission line which is connected between input and output ports is taken as double the feed line impedance while the impedance of the other half wavelength is considered as four times the feed line impedance. The design has obtained bandwidth of more than 60%. It is observed that the full wave electromagnetic results are in good agreement with the experimental and numerical results.

SARS-CoV-2 Mutant Spectra at Different Depth Levels Reveal an Overwhelming Abundance of Low Frequency Mutations.

Populations of RNA viruses are composed of complex and dynamic mixtures of variant genomes that are termed mutant spectra or mutant clouds. This applies also to SARS-CoV-2, and mutations that are detected at low frequency in an infected individual can be dominant (represented in the consensus sequence) in subsequent variants of interest or variants of concern. Here we briefly review the main conclusions of our work on mutant spectrum characterization of hepatitis C virus (HCV) and SARS-CoV-2 at the nucleotide and amino acid levels and address the following two new questions derived from previous results: (i) how is the SARS-CoV-2 mutant and deletion spectrum composition in diagnostic samples, when examined at progressively lower cut-off mutant frequency values in ultra-deep sequencing; (ii) how the frequency distribution of minority amino acid substitutions in SARS-CoV-2 compares with that of HCV sampled also from infected patients. The main conclusions are the following: (i) the number of different mutations found at low frequency in SARS-CoV-2 mutant spectra increases dramatically (50- to 100-fold) as the cut-off frequency for mutation detection is lowered from 0.5% to 0.1%, and (ii) that, contrary to HCV, SARS-CoV-2 mutant spectra exhibit a deficit of intermediate frequency amino acid substitutions. The possible origin and implications of mutant spectrum differences among RNA viruses are discussed.

Discrepancy between the Low-frequency Cutoffs of Type III Radio Bursts Based on Simultaneous Observations by WIND and PSP

The cutoff frequency is an important characteristic parameter of type III radio bursts. Employing the radio data of the Parker Solar Probe (PSP) in the encounter phases of its first five orbits, our previous work revealed that the maximum probability distribution of the cutoff frequency f lo (∼680 kHz) is remarkably higher than that based on Ulysses and WIND (∼100 kHz) investigated by Leblanc et al. and Dulk et al. However, the main influencing factor of the discrepancy is still unknown though the possible reasons are discussed. In this study, we utilize the simultaneous observation by WIND and PSP to analyze statistically the distribution of the cutoff frequency of type III radio bursts, which had not been done before. Based on the automatic Canny edge detection and manual selection, we obtain the f lo of 491 (WIND) and 1194 (PSP) type III bursts from their simultaneous observations in the same solar activity period (from 2019 January 1 to 2020 July 31). The statistical results show that the dominant cutoff frequency measured by PSP (i.e., ∼700 kHz) is still significantly higher than that by WIND (i.e., ∼100 kHz). This implies that radiation attenuation is the main influencing factor for the difference in the statistical results of the cutoff frequency.

Simultaneous switching noise mitigation in high speed pcb using novel planar EBG structure

ABSTRACT Electronic circuits must address electromagnetic interference due to high-speed transmissions and simultaneous switching actions. This paper proposes a design of novel planar EBG structure L Bridge with embedded slit type with 3 × 3 array fashion, which can be used in a plane layer of a printed circuit board to reduce simultaneous switching noise (SSN). Two sets of pattern such as alternate structure and entire embedded pattern are considered and measured the cut-off frequencies. The performance of the structure is simulated, experimentally verified using R&S®ZVH Vector Network Analyser for the frequency range 0.1 to 10 GHz and compared the outcomes. It is observed that for the −50 dB of noise depth, proposed structure is achieved 1.6 GHz to 10 GHz as lower and upper cut-off frequency. In addition, this concluded the noise suppression using equivalent circuit model and parallel plate wave guide theory. Signal integrity on this structure is also analysed with single-ended and differential mode signal transition. Eye pattern is generated and compared for measuring and validating the signal quality while using this EBG structure.

A low profileRFshieldingFSSwith enhanced ultrawide bandwidth range and angular stability

This article describes a frequency selective surface (FSS) for shielding with an improved angular stability over a wide frequency range. The proposed unit design consists of a circular ring in a square element, two cross dipoles, and a T-type slotted structure printed of size 0.052 lambda0 × 0.052 lambda0 on a layer of FR4 substrate having a thickness of 0.0075 lambda0. Here lambda0 is the free-space wavelength of lower cut-off frequency. It has improved the bandwidth range from 2.84 GHz to more than 20 GHz enough to provide effective shielding against the entire ultra-wideband (UWB) range, as well as the X– and Ku–bands. Up to 75 degrees of oblique incidence, the proposed design is polarisation independent and angularly stable. The structure is full wave simulated and an equivalent circuit model is realised. The findings are validated through the use of a fabricated prototype. The applications of shielding are in reducing electromagnetic interference in civil and military applications as well as improving the gain of UWB patch antennas.

Feasibility of applying the lower cut-off frequency for the density radial coverage extension in EAST reflectometry measurement

The extraordinary mode (X-mode) lower cut-off frequency is proposed for use in the reflectometry diagnostic on ITER for the electron density profile measurement, which is a trade-off between extreme plasma parameters and the accessible probing frequency. In contemporary experiments, the lower cut-off frequency can be identified at the probing frequency below the electron cyclotron frequency (f ce) under certain plasma conditions. We provide here, for the first time, the experimental validation of the use of the lower cut-off frequency for the density profiles via the reflectometry measurement on EAST. The corresponding group delay of the lower cut-off frequency evolves continuously with the upper one, revealing a reasonable radial coverage extension of reflectometry measurement toward the plasma core. It is concluded that the lower cut-off frequency can be used as a supplement to the upper one in the density profile inversion process, which is of particular interest in the high magnetic field and/or density discharge to extend the radial coverage of reflectometry measurement.

A Compact Filter Based on Spoof Surface Plasmon Polariton Waveguide for Wide Stopband Suppression

An spoof surface plasmon polaritons (SSPPs) bandpass filter (BPF) supported by trident-shaped complementary grooves is proposed in this letter. Compared with the traditional rectangular-groove SSPP unit cell, the vertical size of the proposed SSPP unit cell is reduced by 40% under the condition of the same asymptotic frequency. Then, a matching feeding structure is introduced by designing microstrip-to-slotline transition (MST) and thus a low cut-off frequency can be obtained. The low cut-off frequency of the passband is determined by the MST structure and the high cut-off frequency of the passband is determined by the SSPP structure. Consequently, a BPF with controllable frequency band and wide stopband suppression is formed by the MST structure and the proposed SSPP structure. Finally, the designed BPF was fabricated and measured. Both numerical and experimental results suggest good filtering performance of the proposed BPF in the frequency band from 2.1 to 8 GHz.

Publisher's Note: Correction of article number for Huang et al 2022 Plasma Sci. Technol. 24 055104

Due to an error in production, an incorrect article number was assigned to the Plasma Science and Technology article 'Feasibility of applying the lower cut-off frequency for the density radial coverage extension on EAST reflectometry measurement' by Jia Huang et al. The original article number was 050001, however the correct citation is:Jia HUANG et al 2022 Plasma Sci. Technol. 24 055104The DOI of the article is unchanged: https://doi.org/10.1088/2058-6272/ac52e9 The relevant abstracting and indexing services have been informed.

RANCANG BANGUN DIGITAL BANDPASS FILTER SEBAGAI APLIKASI SOUND ACTIVATION

The Robot system Of Fire is an intelligent robot, where robot is given artificial intelligence to carry out its tasks, namely robot has to find a fire in a mysterious labyrinth, then perceives it. Sound signal that has 3,8 kHz frequency is needed to enable robot. Sound activation in robot has function to recognize the 3,8 kHz sound signal. Digital bandpass filter is one of digital filter which has function to pass signal that has frequency between lower cutoff frequency and upper cutoff frequency. Analog to digital converter process is used to convert analog signal to digital signal. This process consists of sampling, quantization, and coding. The purpose of this research is applicating digital bandpass filter on sound activation system in order to detect audio source which is 3,8 kHz sound signal.