Triple Filter Research Articles

Second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth

ABSTRACT This paper presents, a novel and simple resonator structure based second order triple band waveguide band-pass filter with adjustable centre frequency and 3-dB bandwidth. The planar insert consists of a circular shape etched part in which three stubs is placed. Three asymmetrical stub length and width are used to control three resonant frequency and 3-dB bandwidth independently. The insert is placed into the transverse plane of the WR-90 waveguide. To achieve second order band-pass filter response two symmetrical resonators is placed at an optimised distance of 8.99 mm. Simulation and optimisation analysis of the proposed filter is carried-out using CST Studio Suite (v23). To validate the 3D model, planar insert and WR-90 waveguide are fabricated individually and inserted manually. The measured results shows triple band bandpass filter characteristics having centre frequencies f 01 = 8.44 GHz, f 02 = 9.98 GHz and f 03 = 11.51 GHz with 3-dB bandwidth of 0.78, 0.12 and 0.3 GHz. The insertion loss of the measured filter is 0.35, 0.8 and 0.55 dB. The in band return loss of the proposed filter are better than 12 dB.

Feasibility of Remote Blood Pressure Estimation via Narrow-band Multi-wavelength Pulse Transit Time

Contact-free sensing gained much traction in the past decade. While remote monitoring of some parameters (heart rate) is approaching clinical levels of precision, others remain challenging (blood pressure). We investigated the feasibility of estimating blood pressure (BP) via pulse transit time (PTT) in a novel remote single-site manner, using a modified RGB camera. A narrow-band triple band-pass filter allowed us to measure the PTT between different skin layers, harvesting information from green and near-infrared wavelengths. The filter minimizes the inter-channel influence and band overlap, however, some overlap remains within the filter bands. We further resolve this using a color-channel model and a novel channel-separation method. Using the proposed setup and algorithm, we obtained multi-wavelength (MW) PTTs in an experiment inducing BP changes to 9 subjects. The results showed good absolute Pearson’s correlation coefficient between both MW PTT and systolic BP (R = 0.61, p = 0.08) as well as diastolic BP (R = 0.54, p = 0.05), pointing to feasibility of the proposed novel remote MW BP estimation via PTT. This was further confirmed in a leave-one-subject-out experiment, where a simple Random Forest regression model achieved mean absolute errors of 3.59 and 2.63 mmHg for systolic and diastolic BP respectively.

Comparative Assessment of Lignan Profiling and Biological Activities of Schisandra henryi Leaf and In Vitro PlantForm Bioreactor-Grown Culture Extracts.

This research's scope encompassed biotechnological, phytochemical, and biological studies of Schisandra henryi, including investigations into its in vitro microshoot culture grown in PlantForm bioreactors (temporary immersion systems, TISs), as well as extracts from leaves of the parent plant, focusing on anti-inflammatory, antioxidant, anticancer, and antimicrobial activities. The phytochemical analysis included the isolation and quantification of 17 compounds from dibenzocyclooctadiene, aryltetralin lignans, and neolignans using centrifugal partition chromatography (CPC), HPLC-DAD, and UHPLC-MS/MS tandem mass spectrometry with triple quadrupole mass filter methods. Higher contents of compounds were found in microshoots extracts (max. 543.99 mg/100 g DW). The major compound was schisantherin B both in the extracts from microshoots and the leaves (390.16 and 361.24 mg/100 g DW, respectively). The results of the anti-inflammatory activity in terms of the inhibition of COX-1, COX-2, sPLA2, and LOX-15 enzymes indicated that PlantForm microshoot extracts showed strong activity against COX-1 and COX-2 (for 177 mg/mL the inhibition percentage was 76% and 66%, respectively). The antioxidant potential assessed using FRAP, CUPRAC, and DPPH assays showed that extracts from microshoot cultures had 5.6, 3.8, and 3.3 times higher power compared to extracts from the leaves of the parent plant, respectively. The total polyphenol content (TPC) was 4.1 times higher in extracts from the in vitro culture compared to the leaves. The antiproliferative activity against T-cell lymphoblast line Jurkat, breast adenocarcinoma cultures (MCF-7), colon adenocarcinoma (HT-29), and cervical adenocarcinoma (HeLa), showed that both extracts have considerable effects on the tested cell lines. The antimicrobial activity tested against strains of Gram-positive and Gram-negative bacteria and fungi showed the highest activity towards H. pylori (MIC and MBC 0.625 mg/mL).

Ancient Wisdom in Pandemic Times: Socrates' Triple Filter Test.

The COVID-19 pandemic is one of the biggest problems in the 21st century with unique characteristics, including its alarming rate of spread and the widespread accumulation of information. In the era of advanced information and communication tools, public understanding comes mainly from social media, which shapes and constructs public opinion and reality. Consequently, this can result in many conflicts on the prevention and treatment of the disease. Paradoxically, although vaccination against COVID-19 has proven its efficacy and safety, it remains a profound issue of debate. Nowadays, we navigated the social media sources to find the answers, as Socrates did navigating in the ancient "agora" to find answers, by conducting the Socratic dialectic method and filtering "information" by the triple filter test. Its aim was to imagine an agitated anti-vaccinist coming to Socrates and saying: "Socrates, I want to tell you some information about vaccination." Socrates: Calm down before listening to what you have to say are you sure that everything you are going to tell me is true? Anti-vaccinist: Well, this personal perception comes mainly from social media. Socrates: So, you cannot know if your information is true or not. Is what you are going to tell me good or not? Anti-vaccinist: You know that I am opposed to vaccination. Socrates: And finally, do you think that this is useful? Anti-vaccinist: Well, I am not quite sure. As Socrates would say, if everything you want to tell us you are not sure is true is not good, as you ignore all the "good" proven data, and is not helpful but rather harmful, this could lead the public opinion to confusion and danger. During this pandemic, where various media construct the reality, "ancient wisdom" may promote a mediating or even a filtering effect between information and untrue, harmful, and useless formations of personal perceptions.

Deep Learning-based Road Segmentation & Pedestrian Detection System for Intelligent Vehicles

Correctly determining the driving area and pedestrians is crucial for intelligent vehicles to reduce fatal road accidents risk. But these are challenging tasks in the computer vision field. Various weather, road conditions, etc., make them difficult. This paper presents a vision-based road segmentation and pedestrian detection system. First, the roads are segmented using a deep learning based consecutive triple filter size (CTFS) approach. Then, pedestrians on the segmented roads are detected using the transfer learning approach. The CTFS approach can create feature maps for small and big features. The proposed system is a reliable, low-cost road segmentation and pedestrian detection system for intelligent vehicles.

High-information data-centric weed images data identification system based on triple filter for smart agriculture

Weeds have seriously impacted crop planting and caused serious human losses. The intelligent weed identification algorithm based on the convolutional neural network has made some achievements in intelligent agriculture. However, the current results rely on a large number of labeled weed data, which is costly to obtain. How to effectively identify without big data is a key task in the current field. We designed a high-information data-centric weed images data identification system based on a triple filter. The system consists of three modules: nearest-neighbor core metric, unobserved components model, and outlier detection. Extensive scientific experiments have shown that our system requires only a small amount of data to achieve excellent performance in weed identification tasks. Our system saves 5% to 20% of the data. When using only 80% of the data, our system achieves the model performance obtained with 100% of data training. Compared with other methods, this method improves the accuracy by 4.9% and reaches a state-of-the-art performance. Our work solves the problem of relying on image data in smart agriculture, provides a scheme for weed identification tasks, and provides valuable ideas for future intelligent agricultural research.

ECG classification system based on multi-domain features approach coupled with least square support vector machine (LS-SVM)

Developing a robust authentication and identification method becomes an urgent demand to protect the integrity of devices data. Although the use of passwords provides an acceptable control and authentication, it has shown much weakness in terms of speed and integrity, which make biometrics the ideal authentication solution. As a result, electrocardiogram (ECG) signals have received a great attention in most authentication systems due to the individualized nature of the ECG signals that make them difficult to counterfeit and ubiquitous. In this paper, we propose a new model for ECG verification using multi-domain features coupled with a least square support vector machine (LS-SVM). Two types of features are investigated to find the best set of features to individual from ECG signals. Time domain and frequency domain features based on optimized Triple Band filter bank are extracted from ECG signals. The extracted features are investigated to figure out the best relevant features and remove the redundant ones. The selected features are fed to three classifiers, including Least Square Support Vector Machine (LS-SVM), K-means, and K-nearest. The obtained results have shown that our ECG biometric authentication system outperforms existing methods. The proposed model obtained an average of accuracy of 88%, 95% with time and frequency features, respectively, while it recorded 99% when a combination of time and frequency features are used to classify ECG signals. A public dataset is used to assess the proposed model.

Semi‐circular mushroom resonator loaded substrate integrated waveguide cavity based compact triple‐band bandpass filter with high selectivity

Two cascaded semi-circular mushroom resonators (ScMRs) loaded to a circular substrate integrated waveguide (CSIW) is used to implement a triple-band bandpass filter of compact size and high selectivity with six transmission zeros (TZs). The ScMRs are coupled to each other along the linear edges of the metal patches and are loaded to the CSIW cavity. A distinctive modification in the schematic and the orientation of the loaded mushroom resonators is carried out along with the introduction of radial coupling slots into the CSIW cavity to generate the three passbands. The TM101 mode is responsible for the generation of first passband. The second and third passbands are formed due to the split odd and even modes of next higher order mode (TM201). An extracted pole is formed within the second passband that splits TM201 mode into odd and even modes. TM201 odd mode (TM201odd) and TM201 even mode (TM201even) are responsible for the generation of second and third passbands, respectively. Here, source-load coupling is employed within the proposed resonator to generate one TZ each at the lower stopband and upper stopband. Two cross-couplings of different modes between two loaded ScMRs are introduced to generate four transmission zeros (TZs) additionally to achieve high selectivity. The triple bandpass filter covering a compact volume of 0.0011 λg3 is fabricated and measured to validate the filter structure. The measured result agrees decently with the simulated one where the passband center frequencies (CFs) of first, second, and third passbands are measured at 1.9, 3.5, and 4.4 GHz with measured insertion losses of 1.5, 1.87, and 1.8 dB, respectively.

A Novel Microstrip Triple Wideband Bandstop Filter Design by Using Adjacent Direct Coupled Dual-Mode Resonators

In this article, a novel triple wideband bandstop filter design is proposed with two adjacent microstrip square loop resonators (MSLR) having different edge lengths. Degenerate modes of the square loop resonators are induced by using direct coupling mechanism. Perturbation and loading elements are located on resonators and used to control reflection zeros between the second and third bands. Even odd mode analysis of a single direct coupled dual-mode resonator is also extracted to elucidate the filter topology. The proposed resonator structure is designed by using a full-wave EM simulator and three different filter responses are obtained from the designed resonator structure. One of the filters is fabricated and, it is observed that measured results are compatible with simulated results.

Imaging pyrometry for most color cameras using a triple pass filter.

A simple combination of the Planck blackbody emission law, optical filters, and digital image processing is demonstrated to enable most commercial color cameras (still and video) to be used as an imaging pyrometer for flames and explosions. The hardware and data processing described take advantage of the color filter array (CFA) that is deposited on the surface of the light sensor array present in most digital color cameras. In this work, a triple-pass optical filter incorporated into the camera lens allows light in three 10-nm wide bandpass regions to reach the CFA/light sensor array. These bandpass regions are centered over the maxima in the blue, green, and red transmission regions of the CFA, minimizing the spectral overlap of these regions normally present. A computer algorithm is used to retrieve the blue, green, and red image matrices from camera memory and correct for remaining spectral overlap. A second algorithm calibrates the corrected intensities to a gray body emitter of known temperature, producing a color intensity correction factor for the camera/filter system. The Wien approximation to the Planck blackbody emission law is used to construct temperature images from the three color (blue, green, red) matrices. A short pass filter set eliminates light of wavelengths longer than 750nm, providing reasonable accuracy (±10%) for temperatures between 1200 and 6000K. The effectiveness of this system is demonstrated by measuring the temperature of several systems for which the temperature is known.

Miniaturized DGS based multi‐band pass filters for satellite applications

This paper presents three types of novel miniaturized single, double and triple band filters using DGS based modified stepped impedance resonator. The modified resonator is linked with square resonators resting on the ground plane. Three types of filters have been proposed with zero rejection, single rejection and double rejection bands. These filters are derived from one another. Hence, there exists some similarity in the filter geometries. However, all the proposed filters are distinct in its design and performance. The double rejection bands are created using half wavelength resonators to reject two different frequency bands. The single rejection band is obtained using F-shaped strip and zero rejection band is obtained using meander etched DGS structure. The proposed triple band-band pass filter (TB-BPF), double band-band pass filter (DB-BPF) and single band-band pass filter (SB-BPF) are simulated and tested with its equivalent prototype. The proposed Type I TB-BPF produces tremendous bandwidth ranges from 2.2 to 4.2 GHz, 4.4 to 7.2 GHz and 8 to 12.8 GHz, Type II DB-BPF operates in two bands such as 2.8–7.9 GHz and 8.2–12.6 GHz and Type III SB-BPF has single pass band from 2.7 to 4.5 GHz. The overall dimension of the filter is achieved to be 0.4 λg × 0.37 λg. Also the measured results are almost matching with simulated results.

QMSIW-Based Single and Triple Band Bandpass Filters

This brief proposes compact and planar substrate integrated waveguide (SIW)-based filters for single and triple band operations using two quarter-mode SIW (QMSIW) cavities. Two miniaturized QMSIW cavity resonators (QMSIWCRs) are capacitively coupled. Miniaturization in the QMSIWCR is achieved by adding an arc-shaped slot and a rectangular open-ended stub at the closed-end of the QMSIWCR. In the triple band bandpass filter (BPF), a capacitor is added to the open-ended side of the stub to enhance impedance matching at the higher modes. It has the centre frequencies of 2.1, 3.98 and 6.6 GHz with an insertion losses (ILs) of 0.93, 0.98, and 1.2 dB at the lower, middle and upper passband, respectively. Moreover, the measured fractional bandwidths (FBWs) are 16.97, 8.77, and 8.42% at the lower, middle and upper passband, respectively. Two rectangular slots are etched on the upper layer of the cavity to suppress the second mode and reduce coupling of the third mode; this realizes a single-band filter with an improved upper stopband response. It has the centre frequency of 2.1 GHz with a wide upper stop-band response, having a rejection level of 20 dB up to 3.19f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> . The operation of filter is additionally discussed and verified by means of a lumped element equivalent circuit model and experimental results. The proposed filters are suitable for integration with other planar radio-frequency (RF) components due to their compact sizes, low ILs, planar structures, multiple transmission zeros (TZs) and adequate bandwidths.

Quantitative 1H and 23Na muscle MRI in Facioscapulohumeral muscular dystrophy patients

ObjectiveOur aim was to assess the role of quantitative 1H and 23Na MRI methods in providing imaging biomarkers of disease activity and severity in patients with Facioscapulohumeral muscular dystrophy (FSHD).MethodsWe imaged the lower leg muscles of 19 FSHD patients and 12 controls with a multimodal MRI protocol to obtain STIR-T2w images, fat fraction (FF), water T2 (wT2), water T1 (wT1), tissue sodium concentration (TSC), and intracellular-weighted sodium signal (inversion recovery (IR) and triple quantum filter (TQF) sequence). In addition, the FSHD patients underwent muscle strength testing.ResultsImaging biomarkers related with water mobility (wT1 and wT2) and ion homeostasis (TSC, IR, TQF) were increased in muscles of FSHD patients. Muscle groups with FF > 10% had higher wT2, wT1, TSC, IR, and TQF values than muscles with FF < 10%. Muscles with FF < 10% resembled muscles of healthy controls for these MRI disease activity measures. However, wT1 was increased in few muscles without fat replacement. Furthermore, few STIR-negative muscles (n = 11/76) exhibited increased wT1, TSC, IR or TQF. Increased wT1 as well as 23Na signals were also present in muscles with normal wT2. Muscle strength was related to the mean FF and all imaging biomarkers of tibialis anterior except wT2 were correlated with dorsal flexion.ConclusionThe newly evaluated imaging biomarkers related with water mobility (wT1) and ion homeostasis (TSC, IR, TQF) showed different patterns compared to the established markers like FF in muscles of FSHD patients. These quantitative biomarkers could thus contain valuable complementary information for the early characterization of disease progression.

Fully tunable filter with cross coupling and reconfigurable transmission zero

In this article, a novel coupling structure is proposed. The surface voltage and current distribution on this structure can be tuned by changing the ratio of the two capacitances so that the central frequency and coupling coefficient can be tuned. The coupling structure can also be tuned to change the sign of coupling coefficient, which is utilized to control the transmission zero of cross coupled tunable bandpass filter. A second order bandpass filter with tunable central frequency and bandwidth is designed and measured. The measurement shows that the central frequency tuning range is 0.768 to 1.512 GHz and the fractional bandwidth tuning range is 0.052 to 0.18 at 1.14 GHz. It shows that the filter can also be tuned with constant fractional bandwidth or constant absolute bandwidth. A tunable cascaded triple bandpass filter with tunable central frequency and bandwidth is designed and measured, as well. The cross‐coupled transmission zero can be configured to locate at either high side or low side of the passband by changing the coupling type of the filter topology.

Diagnostics of ion and electron diffusion in pulsed plasma thrusters using neutral gas injection

Pulsed plasma thrusters (PPTs) have been widely used in space flight applications due to their low cost and robustness. Recently, it has been observed that during the operation of a PPT, the plasma plume exhibits an in-plume acceleration phenomenon where the leading-edge ions continue to accelerate in the plume even in the absence of electromagnetic forces. The physical mechanism behind the phenomenon may be ambipolar diffusion in nature. However, details regarding the propagation of electrons within the plume are still unknown. To better understand the complete plasma diffusion process, it is important to understand the behavior of both ions and electrons. To investigate this mechanism, a diagnostic method using neutral gas injection is proposed to estimate the velocity of fast electrons within the plasma plume. This is a new method where neutral gas is injected at the plasma plume edge to increase the local visible light emission and ionization rate of electrons. In addition to this, a triple Langmuir probe, bandpass filter, and spectrometer were also used to study the plume characteristics. From the experimental results, we estimate that the exhaust velocity of the electrons is over 200 km s−1, roughly an order of magnitude higher than the ion velocity (26 km s−1). The acceleration of ions and the corresponding deceleration of electrons with downstream distance was observed using time-of-flight probe data. Furthermore, the spectral data was also used to identify electron deceleration within the plume. These results further suggest that ambipolar diffusion of electrons and ions may exist in the PPT plume, and that the in-plume acceleration of ions is due to the ambipolar electric field in the plume. Another implication is that depending on the length scales, the plasma plume of the PPT can be non-quasineutrally distributed during the initial period of plume formation.

Study on vehicle driving state and parameters estimation based on triple cubature Kalman filter

Study on vehicle driving state and parameters estimation based on triple cubature Kalman filter

Compact reconfigurable triple notch ultra-wideband bandpass filter for cognitive radio system

This paper introduces a compact ultra-wideband (UWB) bandpass filter (BPF) with two switchable external notch structures which avoids the interference between the UWB communication with worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems, suitable for cognitive radio (CR) applications. The first external notch structure is modified C-shaped structure which generates a sharp rejection at 3.5 GHz to avoid interference with WiMAX system and second external notch structure is back to back T-shaped structure which creates sharp rejection notch bands at 5.2 GHz and 5.8 GHz frequencies for WLAN systems. The filter reconfiguration is achieved by varying the conductance of microstrip line. The response of the proposed structure shows sharp rejections at one WiMAX and two WLAN bands. The bandpass filter covers frequency of UWB system from 3.1 to 10.7 GHz having very low passband insertion loss. The proposed UWB BPF is designed, simulated, fabricated and tested to validate the results. A good agreement is achieved between simulation and experimental results.

Compact reconfigurable triple notch ultra-wideband bandpass filter for cognitive radio system

This paper introduces a compact ultra-wideband (UWB) bandpass filter (BPF) with two switchable external notch structures which avoids the interference between the UWB communication with worldwide interoperability for microwave access (WiMAX) and wireless local area network (WLAN) systems, suitable for cognitive radio (CR) applications. The first external notch structure is modified C-shaped structure which generates a sharp rejection at 3.5 GHz to avoid interference with WiMAX system and second external notch structure is back to back T-shaped structure which creates sharp rejection notch bands at 5.2 GHz and 5.8 GHz frequencies for WLAN systems. The filter reconfiguration is achieved by varying the conductance of microstrip line. The response of the proposed structure shows sharp rejections at one WiMAX and two WLAN bands. The bandpass filter covers frequency of UWB system from 3.1 to 10.7 GHz having very low passband insertion loss. The proposed UWB BPF is designed, simulated, fabricated and tested to validate the results. A good agreement is achieved between simulation and experimental results.

Performance enhancement of dielectric resonator antenna by using cross-resonator based filtering feed-network

A wideband filtering dielectric resonator antenna (DRA) is demonstrated in this paper. The filtering characteristics is obtained by integrating a triple pole cross-resonator filter in the feed line of the slot coupled rectangular DRA. The transmission poles of the resonator are adjusted in order to get the wideband filtering response. The proposed filtering DRA offers an impedance bandwidth of 15% from 3.06 GHz to 3.56 GHz. Electric field distribution of DRA within the passband confirmed that the rectangular DRA drives in TE111 mode which ensured the broadside radiation. A satisfactory stable gain pattern of 5.9 ± 0.3 dBi within the pass-band has been achieved. The gain response falls sharply with two radiation-nulls beyond the passband at 3.9 GHz and 4.4 GHz and that increases the selectivity of the antenna. In conclusion, proposed design offers a robust technique to convert a conventional slot coupled rectangular DRA into a wideband antenna along with frequency selective gain response. Proposed configuration manifests as an ideal contender for some specific uses in S-band such as Wi-Max, TD-LTE (Time-Division Long Term Evaluation) application as it avoids the interference adjacent bands.

Multilayer triple band bandpass filter with a floating U-shaped SIR and split ring resonator

A multiple band bandpass filter (BPF) is designed using multilayer arrangement. The bandpass filter has three passbands having centre frequencies at 2.45 GHz, 4 GHz and 5 GHz. First a single band BPF is designed which includes a pair of coupled resonator and a split ring resonator in a multilayer arrangement. This geometry of the filter structure is studied and validated by fabrication and measurement. The initial single band filter structure is further improved to provide triple band BPF. All these bands are realized by a stub loaded U-shaped step impedance resonator (SLU-SIR). However, to improve the response of the second and third band a modified split ring resonator and a pair of open stubs are used. Each passband can be controlled individually. A mathematical analysis is done to study the proposed SLU-SIR using transmission line model. The proposed filter provides compactness and low insertion loss. A prototype is measured using vector network analyser (VNA) and shows a good matching with the simulated result.