Notch Frequency Research Articles

Microwave planar resonator-based sensor for pharmaceutical tablet-moisture characterization based on complementary symmetric meander line-shaped structure

ABSTRACT This paper presents a microwave planar resonator-based sensor for moisture sensing application. The resonator sensor is designed utilising the Complementary Symmetric Meander Line-Shaped Resonator topology and operated in the S-band with the frequency range of 2.6–3.3 GHz. The main design criteria of this sensor are based on low manufacturing complexity and cost, ease of fabrication and integration with existing equipment, despite its high sensitivity and accuracy. When this sensor is loaded/unloaded with four different Material Under Tests with relative permittivity values varying from 2.3 to 4.3, the electromagnetic simulations were validated against experimental measurements according to the resonant notch frequency of transmission coefficient for the sensor’s material-characterisation performance. The simulated and experimental results show good agreements on the resonant frequencies and demonstrate the sensor’s high performance with a normalised sensitivity of 6%. Resonant frequencies are well correlated with material permittivity using a quadratic-polynomial regression with R 2 = 0.999. Moreover, moisture-content percentages of both dry and moist paracetamol tablets, measured by a loss-on-drying moisture analyser between 1.74% and 17.72%, have good correlation with the sensor’s resonant-frequency shift from on-line measurements. This resonator sensor has exhibited the potential for detecting moisture contents in small-sized materials in various industries.

Simplified modeling of elastic guided waves in a pre-stressed cable

Elastic waves can be employed to probe the mechanical state of pre-stressed cables and look for defects in critical areas. Contacts between wires have been shown to play a major role in wave propagation by giving rise to tension-dependent phenomena such as anomalous transmission at certain frequencies (the "notch frequency effect"). Here, we present a simplified way of modeling the free propagation of waves at low frequencies by analytically accounting for contacts. Wires are described within beam theory and connected with tension-dependent springs derived from Hertz law. In contrast to point-wise contacts, these line-wise contacts also induce second-neighbor coupling, i.e. they connect wires that are not in direct contact one another. The simplified model is compared with a reference model based on a finite elements representation of the cross section ("SAFE" method). The range of validity in frequency is discussed. The results provide a new interpretation for the first higher order modes in and their dependence with tension in terms of contact resonances. The drastic reduction of numerical costs suggests the method could be applicable to more complex civil engineering cables, composed of many wires.

The 140 GHz notch filter development for millimeter-wave diagnostics protection on the stellarator Wendelstein 7-X

The notch filter plays a crucial role as a protective component in microwave diagnostics, primarily by addressing issues related to catastrophic interference. Designed for millimeter-wave diagnostics on the stellarator Wendelstein 7-X (W7-X), a WR-6 waveguide-based notch filter has been successfully developed to effectively isolate leakage from auxiliary heating gyrotrons operating at 140 GHz. The filter incorporates cylindrical cavities resonating at 140 GHz for the TE11p mode, with coupling structures that are designed and optimized for high-efficiency coupling. This configuration simplifies fabrication, thereby ensuring high-yield production. Experimental fabrication and in-house characterization confirm the notch filter's exceptional performance, with over 60 dB rejection in the vicinity of 140 GHz and low insertion loss (< 2 dB) above and below the notch frequency across a broad frequency bandwidth (121–138 GHz, 142–163 GHz). The utilization of this high-frequency structure fabrication technology can be applied to millimeter-wave diagnostics on other machines. In addition to the design elements of the notch filter, this paper also provides a detailed discussion of the fabrication process and methodology.

Sintilimab (anti-PD-1 antibody) combined with high-dose methotrexate, temozolomide, and rituximab (anti-CD20 antibody) in primary central nervous system lymphoma: a phase 2 study

Primary central nervous system lymphoma (PCNSL) is a rare and frequently fatal lymphoma subtype. The programmed death-1 (PD-1) pathway has emerged as a potential therapeutic target, but the effectiveness of PD-1 antibody sintilimab in combination with immunochemotherapy as a frontline treatment for PCNSL remains to be determined. In this phase 2 trial (ChiCTR1900027433) with a safety run-in, we included patients aged 18–70 with newly diagnosed PCNSL. Participants underwent six 21-day cycles of a SMTR regimen, which includes sintilimab (200 mg, Day 0), rituximab (375 mg/m2, Day 0), methotrexate (3.0 g/m2, Day 1 or 1.0 g/m2 for patients aged ≥65 years), and temozolomide (150 mg/m2/d, Days 1–5). Among 27 evaluable patients, the overall response rate (ORR) was 96.3% (95% confidence interval: 81–99.9%), with 25 complete responses. At a median follow-up of 24.4 months, the medians for duration of response, progression-free survival (PFS), and overall survival were not reached. The most common grade 3–4 treatment-related toxicities were increased levels of alanine aminotransferase (17.9%) and aspartate aminotransferase (14.3%). Additionally, baseline levels of interferon-α and the IL10/IL6 ratio in cerebrospinal fluid emerged as potential predictors of PFS, achieving areas under the curve of 0.88 and 0.84, respectively, at 2 years. Whole-exome sequencing revealed a higher prevalence of RTK-RAS and PI3K pathway mutations in the durable clinical benefit group, while a greater frequency of Notch and Hippo pathway mutations in the no durable benefit group. These findings suggest the SMTR regimen is highly efficacious and tolerable for newly diagnosed PCNSL, warranting further investigation.

Handling Qualities Assessment and Discussion for Helicopter with Slung Load Systems Utilizing Various Sling Configurations

Sling configurations significantly influence the coupled dynamics of the helicopter with slung load system (HSLS), resulting in alterations to handling qualities (HQs) that remain inadequately understood. This study introduces a computer-oriented, generalized method for constructing the HSLS model with various sling configurations. To evaluate the HQs of 1-point, 2-point, and 4-point sling configurations, both the stability and response criteria outlined in ADS-33E and a newly proposed criterion for slung loads towards the updated ADS-33F were employed. Modal analysis was conducted to elucidate the coupled mechanisms of the HSLS under different sling configurations. The findings reveal that the dynamics of the main rotor can attenuate the lateral swing motions of the load in the 4-point sling configuration. While multiple-point sling configurations can enhance the helicopter’s bandwidth, they also amplify the magnitude notch in the helicopter’s response. Nevertheless, when a larger hook distance is employed, the notch frequency is sufficiently distant from the load swing bandwidth, leading to a reduced degradation in HQs. A 4-point configuration with lateral and longitudinal hook distances equal to twice the width and length of the slung load is recommended in practice to achieve sufficient swing stability and mitigate HQ degradation.

High Broadband Optical Absorption and Bandstop Filter Characteristics of Pb/Nb2O5 Interfaces

AbstractIn this study, semitransparent lead films serve as substrates for depositing niobium pentoxide thin films, forming versatile electro‐optical devices. Using vacuum evaporation and ion sputtering techniques at ≈10−5 mbar, stacked layers of crystalline Pb and amorphous Nb2O5 are created. This process reduces free carrier absorption in Nb2O5 and forms Urbach tail states with a width of 0.91 eV. Pb/Nb2O5 thin films exhibit remarkable broadband absorption, exceeding 440% in the visible and 98% in the infrared. Moreover, Pb substrates induce a redshift in Nb2O5’s energy bandgap. Electrical analysis using impedance spectroscopy on Pb/Nb2O5/Ag structures reveals their series/parallel resonance and bandstop filter properties. Notably, the bandstop filters exhibit reflection coefficient minima at a notch frequency of 1.66 GHz, with a bandwidth of 280 MHz, return loss of 26 dB, and voltage standing wave ratio of 1.13. These findings underscore the device's potential for wide‐ranging electro‐optical applications across the electromagnetic spectrum.

A quad port dual band notch UWB MIMO antenna using hybrid decoupling structure

A four-port dual-band notch ultrawideband (UWB) multiple input and multiple output (MIMO) antenna for automotive applications is presented. Initially, a circular patch monopole antenna is designed and optimized by embedding a rectangular stub onto the radiator and lowering the ground plane to realize the UWB frequency spectrum. The dual-band frequency notch, from 4.6 to 5.9 and 6.8–8.8 GHz, is achieved using a half wavelength slot onto the feedline and a pair of H-shaped stubs across the feedline, respectively, to cover WLAN and complete x-band satellite communication. Further, the designed dual-band notch UWB antenna is transformed to a four-port MIMO antenna with interelement spacing much smaller than λ/4 (λ at 3.1 GHz) and a size of 0.46 × 0.41 × 0.01 λ3. Isolation improvement is achieved by a hybrid decoupling technique comprising a distinctive neutralization line (NL) and defected ground structure (DGS). The average isolation of the proposed design is better than 22 dB. Characteristic mode analysis of the proposed antenna is performed to analyze the specific significant mode and their contribution to the antenna radiation. The antenna design's diversity and time-domain properties are analyzed and found suitable for automotive applications. The antenna's electromagnetic interaction with the electrically large structure is studied by mounting the antenna onto an open-source automobile model, and the gain is determined to be more than 6.1 dB at the antenna's resonant frequencies.

Improved ADRC Current Low‐Frequency Ripple Suppression Strategy Based on VFNF

AbstractIn the two‐stage inverter system, due to the space vector modulation (SVM), the midpoint potential of active neutral point clamped three‐level inverter system (ANPC‐TLIS) will have triple frequency fluctuation, under the influence of the closed‐loop control strategy, the fluctuation amplitude of the lithium battery energy storage system (LBESS) output current will increase. To reduce the low‐frequency output current fluctuation, a voltage loop strategy based on active disturbance rejection control (ADRC) with notch filter (NF)is proposed in this paper. In this scheme, the voltage outer‐loop control strategy not only maintains voltage stability, but also reduces the fluctuation amplitude of reference current. In addition, during the electromagnetic transient process, the LBESS output current fluctuation frequency is constantly changing because the power supply frequency required by linear motor is constantly changing. To solve this problem, the inverter output current frequency is feedforward to the LBESS controller, forming a variable frequency notch filter (VFNF). Finally, the effectiveness of the proposed strategy is verified by fixed‐frequency and variable frequency conditions experiments on RT‐LAB experimental platform. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC.

Compact design of MIMO antenna with split ring resonators for UWB applications

In recent times, the Multiple-Input Multiple-Output (MIMO) system has played a vital role in wireless communication. MIMO antenna uses multiple antennas on both the sides of the transmitter and receiver. Mutual coupling occurs between two antenna elements to reduce the performance. The passage of current in the same direction on both neighbouring sides of the antennas increases the rate of mutual coupling. To decrease the mutual coupling, Split Ring Resonators (SRR) are located on the MIMO antenna. In this research paper, a MIMO antenna with SRR for Ultra Wide Band (UWB) applications with different frequency notches is proposed. Also, bandwidth and isolation are considered essential metrics for MIMO antennas. In the proposed 4 × 4 MIMO antenna design, SRR is located at the antenna's two sides, and the defected ground structure is on the bottom portion with a permittivity of 4.4 (FR4 substrate). The defected ground structure is proposed with stubs to enhance the characteristics of bandwidth and create notch bands in the frequency range of 3.1 GHz to 10.6 GHz. Placing SRRs adjacent to the feed line enhances the gain performance. The experimental results show that the ECC of the proposed antenna is less than 0.25, DG is higher than 9.8 dB, and the peak realized gain for 9.38 GHz is 11.3 dB, which is more reliable than other antenna designs. Therefore, experimental outcomes of the proposed antenna design enhance the applicability of band notching for wideband communication.

Current coordinated distribution and voltage optimization control for multi-VSGs system considering nonlinear and negative sequence loads

In a microgrid system where multiple virtual synchronous generators (VSGs) are interconnected through high impedance cables, the total output negative sequence and harmonic current of multiple VSGs cannot be coordinated based on the capacity of each power conversion system (PCS). In addition, there is significant distortion in the voltage at the point of common coupling (PCC). Because the impedance amplitude and impedance angle of the cable change with the harmonic frequency, the resistive virtual impedance reshaping method and fixed impedance angle virtual impedance reshaping method used in the current research cannot solve the harmonic current distribution problem. To solve the above problems, a multi-frequency points VSG impedance reshaping control strategy is proposed in this paper, which can adjust the resistive and inductive output impedance of each harmonic frequency independently. The strategy is based on the harmonic separation algorithm of LPF with Feedforward Compensation (FCLPF) and the voltage controller of Vector Proportional Integral (VPI) in fundamental dq rotation coordinate system, which effectively improve the flexibility and accuracy of harmonic impedance reshaping. Among them, FCLPF harmonic separation algorithm has the characteristics of target frequency bandpass and non-target frequency notch, and can eliminate the coupling interference of each harmonic virtual impedance when accumulating virtual impedance voltage references at various frequency points. The closed-loop transfer function of the multi-parallel VPI voltage controller has the characteristics of unit gain and zero phase shift at each harmonic frequency point, which means the static response error of virtual impedance voltage command can be almost completely eliminated. Under the proposed control strategy, the fundamental positive power can be allocated according to the droop coefficient, the fundamental negative current and harmonic current can be allocated according to the sum of the reshaped virtual impedance and the actual line impedance. Reshaping virtual impedance at each harmonic frequency to negative value can also compensate the harmonic voltage drop on the high impedance cable and improve the voltage quality at the PCC.

Improvement in notch band characteristics of a hexagonal super wideband antenna by interfering back radiation out of phase with front radiation using frequency selective surface

SummaryA band‐notched super wideband (SWB) planar monopole antenna with improved notch characteristics is proposed in this article. A hexagonal SWB antenna operating in the frequency range from 3.04 to 36 GHz is initially designed on Arlon substrate. The hexagonal patch is then loaded with optimum sized U‐shaped slot to eliminate WLAN band (5.15–5.85 GHz). The notch band's characteristics are further improved by incorporating a frequency selective surface (FSS) of a square array at a specific distance below the antenna to introduce a phase delay of 180° between the back radiation reflected by the FSS with the front radiation at the notched frequency. Improvement of notch band gain, efficiency, and antenna front‐to‐back ratio (FBR) are studied. The antenna without embedding an FSS exhibits working spectrum from 3.1 to 33.6 GHz with notch frequency gain of −2.6 dBi and efficiency 53%. The inclusion of an FSS layer at 25.2 mm behind the antenna results in notch frequency gain of −7.6 dBi with an efficiency of 23%. FBR improvement of about 16 dB is achieved at 8 GHz, and FBR is reduced by about 5 dB at the notch frequency. 169% fractional bandwidth with bandwidth dimension ratio (BDR) of 1622 is achieved in this proposed FSS integrated antenna. The inclusion of FSS to improve the band elimination performance represents the novelty of this proposal. The data are validated by electromagnetic simulation and physical measurement techniques.

A Cross-Polarization Converter Using Guided Wave Inspired Metasurface With an In-Band Notch and High Frequency Selectivity

A Cross-Polarization Converter Using Guided Wave Inspired Metasurface With an In-Band Notch and High Frequency Selectivity

Notch band characteristics improvement of a printed ultra wideband antenna by embedding frequency Selective Surface

Excellent improvement on band notched characteristics of a circular ultra-wideband (UWB) printed antenna by embedding Frequency Selective Surface (FSS) at proper position in the far field is presented in this article. A square shaped mushroom Electromagnetic Band Gap (EBG) structure is placed beside the feeding line to achieve an elimination band of 3.7–4.2 GHz over the ultra-wideband range of 2.9–14 GHz showing fractional bandwidth of 131 %. The proposed antenna's electrical dimension is 0.29λ×0.367λ×0.015λ. After embedding the properly designed FSS at optimal position along with the antenna the maximum gain of the radiating frequency increases from 7.1 dBi to 8.1 dBi and notch frequency gain reduces to −7.9 dBi from −5 dBi. Radiation efficiency at notch frequency also reduces from 31 % to 17 %. More than 10 dB Front to Back lobe Ratio (FBR) is obtained at 4.5 GHz. With the aid of Advanced Design Software (ADS), an equivalent circuit for the suggested antenna is created and its response is contrasted with measured and simulated outcomes. The proposed antenna is useful in UWB range with band rejection for C band satellite downlink.

Second‐harmonic current reduction of dual active bridge with triple‐phase shift in two‐stage single‐phase inverter system

AbstractThis article proposes a method to effectively suppress second‐harmonic current (SHC) of dual active bridge (DAB) converter, which adopts the triple‐phase shift (TPS) modulation strategy, in two‐stage single‐phase inverter system. Load current feedforward control with twice the output voltage frequency notch filter inserted is introduced to ensure the dynamic response performance. The averaged model of the system is established to analyse the influence of output impedance of front‐end DAB converter on SHC from the perspective of impedance. The proposed method does not need to consider the accuracy of the intermediate bus capacitance. Finally, an experimental prototype was established to verify the correctness and effectiveness of the proposed SHC reduction method.

Design of a superconducting UWB bandpass filter with tunable notch band

By studying the principles of ultra-wideband (UWB) and band-stop, a novel band-pass filter with adjustable band-stop characteristics is proposed. The filter achieves 3.1-10.6 GHz UWB bandpass characteristics through an improved multi-mode resonator. An L-shape λ/2 notch resonator loaded with a 2-bit reconfigurable interdigital capacitor (IDC) array is coupled to the multiple-mode resonator and generates a tunable notch band to reject any undesired signal that may interfere with the UWB passband. By connecting the IDC to the ground or not, the capacitance of each IDC and the corresponding notch frequency can be adjusted. After design and optimization, the final size of the superconducting filter is 20.0 mm × 6.9 mm, and the test results and simulation results are highly consistent.

A Modified Iterative Learning Control Approach for the Active Suppression of Rotor Vibration Induced by Coupled Unbalance and Misalignment

This paper proposes a modified iterative learning control (MILC) periodical feedback-feedforward algorithm to reduce the vibration of a rotor caused by coupled unbalance and parallel misalignment. The control of the vibration of the rotor is provided by an active magnetic actuator (AMA). The iterative gain of the MILC algorithm here presented has a self-adjustment based on the magnitude of the vibration. Notch filters are adopted to extract the synchronous (1 × Ω) and twice rotational frequency (2 × Ω) components of the rotor vibration. Both the notch frequency of the filter and the size of feedforward storage used during the experiment have a real-time adaptation to the rotational speed. The method proposed in this work can provide effective suppression of the vibration of the rotor in case of sudden changes or fluctuations of the rotor speed. Simulations and experiments using the MILC algorithm proposed here are carried out and give evidence to the feasibility and robustness of the technique proposed.

Cross-Modal Tinnitus Remediation: A Tentative Theoretical Framework.

Tinnitus is a prevalent hearing-loss deficit manifested as a phantom (internally generated by the brain) sound that is heard as a high-frequency tone in the majority of afflicted persons. Chronic tinnitus is debilitating, leading to distress, sleep deprivation, anxiety, and even suicidal thoughts. It has been theorized that, in the majority of afflicted persons, tinnitus can be attributed to the loss of high-frequency input from the cochlea to the auditory cortex, known as deafferentation. Deafferentation due to hearing loss develops with aging, which progressively causes tonotopic regions coding for the lost high-frequency coding to synchronize, leading to a phantom high-frequency sound sensation. Approaches to tinnitus remediation that demonstrated promise include inhibitory drugs, the use of tinnitus-specific frequency notching to increase lateral inhibition to the deafferented neurons, and multisensory approaches (auditory-motor and audiovisual) that work by coupling multisensory stimulation to the deafferented neural populations. The goal of this review is to put forward a theoretical framework of a multisensory approach to remedy tinnitus. Our theoretical framework posits that due to vision's modulatory (inhibitory, excitatory) influence on the auditory pathway, a prolonged engagement in audiovisual activity, especially during daily discourse, as opposed to auditory-only activity/discourse, can progressively reorganize deafferented neural populations, resulting in the reduced synchrony of the deafferented neurons and a reduction in tinnitus severity over time.

Ultrathin Platinum Film Hydrogen Sensors with a Twin-T Type Notch Filter Circuit.

In recent years, hydrogen energy has garnered attention as a potential solution for mitigating greenhouse gas emissions. However, concerns regarding the inherent risk of hydrogen gas leakage and potential explosions have necessitated the development of advanced sensors. Within our research group, we have innovated an ultrathin platinum (Pt) film hydrogen sensor that gauges resistance changes in Pt thin films when exposed to hydrogen gas. Notably, the sensitivity of each sensor is contingent upon the thickness of the Pt film. To address the challenge of detecting hydrogen using multiple sensors, we integrated the ultrathin Pt film as a resistance element within a twin-T type notch filter. This filter exhibits a distinctive reduction in output signals at a specific frequency. The frequency properties of the notch filter dynamically alter with changes in the resistance of the Pt film induced by hydrogen exposure. Consequently, the ultrathin Pt film hydrogen sensor monitors output signal variations around the notch frequency, responding to shifts in frequency properties. This innovative approach enables the electrical control of sensor sensitivity by adjusting the operating frequency in proximity to the notch frequency. Additionally, the simultaneous detection of hydrogen by multiple sensors was successfully achieved by interconnecting sensors with distinct notch frequencies in series.

Noise-induced Hearing Loss: Continuous versus Impact/impulse Noise.

Impact/impulse and continuous noise are two main causes of noise-induced hearing loss (NIHL) in workplaces. The aim of this study was to compare the effects of impulse/impact noise and continuous noise on hearing status. In this study, 259 workers referred to the occupational medicine clinic of Shahid Rahnemoun hospital, Yazd, Iran, entered the study and were divided into two groups: with exposure to impact/impulse noise and with exposure to continuous noise. Hearing thresholds were measured and compared between the two groups by pure-tone audiometry (PTA). The frequency of hearing loss and audiometric notch according to the results of PTA was compared between the two groups. Data were analyzed by SPSS (ver. 16) using Student's t-test, Chi-square test, and Mann-Whitney U test. Hearing thresholds were significantly higher at all frequencies in the impact noise group. The hearing threshold at 6000 Hz was higher than other frequencies in both groups. The frequency of hearing loss at high frequencies was higher in the impact group. The frequency of audiometric notch was not significantly different between the two groups. The results of this study showed that hearing loss after exposure to impact/impulse noise is probably more frequent and more severe than exposure to continuous noise, but the pattern of hearing loss is similar in both types of noise exposure.

Diagnosis of attention deficit hyperactivity disorder: A deep learning approach

&lt;abstract&gt; &lt;p&gt;In recent years, there has been significant interest in the analysis and classification of brain dis-orders using electroencephalography (EEG). We presented machine learning and deep learning (DL) frameworks that integrate an EEG-based brain network with various DL models to diagnose attention deficit hyperactivity disorder (ADHD). By incorporating an objective biomarker into the diagnostic process, the accuracy and effectiveness of diagnosis could be enhanced. We used public EEG datasets from 61 ADHD youngsters and 60 normally developing children. The raw EEG data underwent preprocessing, including the application of filters in clinically relevant frequency bands and notch filters. From the preprocessed EEG segments, statistical features (e.g., standard deviation, kurtosis) and spectral features (e.g., entropy) were extracted. Principal component analysis (PCA) and chi-square with PCA were used as feature selection methods to obtain the most useful features and keep them. The machine learning models achieved the highest accuracy result of 94.86% by utilizing support vector machines (SVM) with PCA features. Furthermore, integrating models combining a convolutional neural network (CNN) with bidirectional long short-term memory (BiLSTM) networks, and gated recurrent unit-Transformer (GRU-Transformer block) with Chi-square and PCA features achieved accuracies of 94.50% and 95.59%, respectively. The suggested framework demonstrated a wide range of applicability in addressing the identification of ADHD. To evaluate the performance of the proposed models, comparisons were made with existing models, and the proposed system exhibited superior performance. We enhanced EEG-based analysis and categorization of ADHD by demonstrating the capabilities of advanced artificial intelligence models in enhancing diagnostic accuracy and efficacy.&lt;/p&gt; &lt;/abstract&gt;