Channel Filter Research Articles

A Novel Triplexer Based on SISL Platform

In this paper, a novel triplexer using the substrate-integrated suspended line technology is proposed. Two matching circuits are designed to connect the three filter channels for the triplexer construction. The used bandpass filters are composed of a low-pass filter and a high-pass filter, and they have advantages of high controllability and low insertion loss. For the proposed triplexer, two adjacent filter channels compose a duplexer. Based on the design consideration, the triplexer can be extended to a multiplexer. The proposed design is further improved by using a patterned suspended substrate for loss reduction. The triplexer achieves good isolations among the three ports and low insertion losses of 1.4/1.3/0.8 dB for the three channels of 0.8, 2.5, and 5.8 GHz, respectively.

Optimal Design of Multiplier-Less Non-uniform Channel Filters with Successive Approximation of Vectors

Applications such as software-defined radio (SDR) receivers utilize channel filters to isolate the individual frequency bands of different communication standards present in a wideband input signal. Low complexity and sharp transition width are the two important design constraints of channel filters in SDR receivers. Frequency response masking (FRM) with the multiplier-less design is an effective approach for designing sharp filters with low complexity. This paper presents an optimal design for multiplier-less implementation of FRM-based non-uniform channel filters. In the proposed design, multiplier-less channel filters are realized basing upon decomposing their impulse response values in generalized bit planes. This decomposition is based on a vector successive approximation technique in which impulse responses are successively approximated using a dictionary of vectors. The resulting coefficients of channel filters belong to signed sums of powers of two form. The proposed channel filter designs are simulated using MATLAB R2017b, and the results have been compared with the existing ones in order to signify the effectiveness of the proposed design. The simulations show that the proposed channel filter design has low complexity (number of adders) and the design time is considerably low.

Development of a Multimode Field Deployable Lidar Instrument for Topographic Measurements of Unsaturated Soil Properties: Instrument Description

The hydrological and mechanical behavior of soil is determined by the moisture content, soil water (matric) potential, fines content, and plasticity. However, these parameters are often difficult or impractical to determine in the field. Remote characterization of soil parameters is a non-destructive data collection process well suited to large or otherwise inaccessible areas. A ground-based, field-deployable remote sensor, called the soil observation laser absorption spectrometer (SOLAS), was developed to collect measurements from the surface of bare soils and to assess the in-situ condition and essential parameters of the soil. The SOLAS instrument transmits coherent light at two wavelengths using two, continuous-wave, near-infrared diode lasers and the instrument receives backscattered light through a co-axial 203-mm diameter telescope aperture. The received light is split into a hyperspectral sensing channel and a laser absorption spectrometry (LAS) channel via a multi-channel optical receiver. The hyperspectral channel detects light in the visible to shortwave infrared wavelengths, while the LAS channel filters and directs near-infrared light into a pair of photodetectors. Atmospheric water vapor is inferred using the differential absorption of the on- and off-line laser wavelengths (823.20 nm and 847.00 nm, respectively). Range measurement is determined using a frequency-modulated, self-chirped, coherent, homodyne detection scheme. The development of the instrument (transmitter, receiver, data acquisition components) is described herein. The potential for rapid characterization of physical and hydro-mechanical soil properties, including volumetric water content, matric potential, fines content, and plasticity, using the SOLAS remote sensor is discussed. The envisioned applications for the instrument include assessing soils on unstable slopes, such as wildfire burn sites, or stacked mine tailings. Through the combination of spectroradiometry, differential absorption, and range altimetry methodologies, the SOLAS instrument is a novel approach to ground-based remote sensing of the natural environment.

A KU-BAND FILTERING DUPLEX ANTENNA FOR SATELLITE COMMUNICATIONS

In this paper, a dual-polarisation shared-aperture duplex antenna is presented for satellite communications at the standard microwave Ku-band, based on the integrated filtering-antenna concept and co-design approach. The design relies on the use of resonators coupled to the radiating dual-band dual-polarisation antenna. The resonant patch antenna forms one pole of each channel filter, resulting in a third-order filter in the Rx channel and a second-order filter in the Tx channel. The Rx and Tx ports of the antenna take in horizontal and vertical linear polarisations, respectively. The integrated duplexer helps to increase the isolation between the ports and the selectivity of each channel. The integration between the filter and the antenna is achieved by electromagnetic coupling, without the need of external matching circuits. Thus it attains a compact footprint. The operation frequencies of the demonstrated duplexantenna are from 11 to 12.5 GHz (12.8%) for the downlink to the Rx port, and from 13 to 14.4 GHz (10.2%) for the uplink at the Tx port. High port-to-port isolation of over 40 dB is realized to reduce channel interference. Flat in-band average gains are achieved to be 8.3 and 8.6 dBi, for the low- and high-bands, respectively.

Guided-mode resonant narrowband terahertz filtering by periodic metallic stripe and patch arrays on cyclo-olefin substrates

We experimentally and theoretically demonstrate a class of narrowband transmissive filters in the terahertz spectrum. Their operation is based on the excitation of guided-mode resonances in thin films of the low-loss cyclo-olefin polymer Zeonor, upon which aluminum stripe and patch arrays are patterned via standard photolithography. The filters are engineered to operate in low atmospheric loss THz spectral windows, they exhibit very high transmittance and quality factors, compact thickness, and mechanical stability. The dependence of their filtering properties on the geometrical parameters, the substrate thickness and the angle of incidence is investigated, discussing the physical limitations in their performance. This class of filters provides a cost-effective solution for broadband source or channel filtering in view of emerging terahertz wireless communication systems.

Plasmonic multi channel filter based on split ring resonators: Application to photothermal therapy

In this study, we developed and analyzed a multichannel filter based on multiple plasmonic split ring resonators. In the proposed structure, split ring resonators were coupled to T-shaped and straight waveguides. The field distribution and transmission characteristics were investigated using the finite-difference time-domain method. In the proposed filter, the split ring resonators, and straight and T-shaped waveguides were made of air situated in a silver background. The proposed structure can confine light to sub-wavelength dimensions and it can be utilized in photonic integrated circuits. The results showed that the proposed structure functioned as a typical filter and the electromagnetic wave energy at different wavelengths could be trapped in different insulator rings. The sensitivity factors and dependence of the multichannel filter on the coupling lengths (Li) and ring widths (Ci) were also investigated. Based on the linear relationships with the refractive indices and resonance wavelengths in the ring resonators, sensitivity factors could be obtained for different rings. By increasing the refractive index, the resonance wavelengths exhibited considerable red shifts. The proposed structure with high transmission efficiencies and resonance wavelength ranges (near infrared) will be useful in highly integrated optical circuits, photothermal therapy, and cancer treatment.

Connecting Society and Policymakers? Conceptualizing and Measuring the Capacity of Civil Society Organizations to Act as Transmission Belts

Civil Society Organizations (CSOs) are considered important intermediaries between citizens and policymakers. They are assumed to function as transmission belts that filter societal preferences and channel them to policymakers. Although the ability of CSOs to connect civil society with policymakers has been put into question, it has rarely been theoretically specified and empirically tested. This paper develops a conceptualization of CSOs that examines their capacity to function as transmission belts. It does so by distinguishing two organizational dimensions related to member involvement and organizational capacity. The paper draws on a large survey of CSOs active at the EU to empirically assess these organizational dimensions and relate them to basic CSOs’ characteristics. The findings indicate that one out of three organizations approximates the ideal-type transmission belt. The findings contribute to a better understanding and assessment of CSO’s potential contribution to policy-making in representative democracies.

GNSS/MEMS IMU ultra‐tightly integrated navigation system based on dual‐loop NCO control method and cascaded channel filters

A coherent scheme of federated architecture for the ultra-tight integration of global navigation satellite system (GNSS) and MEMS (micro-electro-mechanical system) inertial measurement unit (IMU) is presented. Inside the receiver baseband, both the controls for code numerically controlled oscillator (NCO) and carrier NCO are designed. They are each composed of two parts, one part is derived from the navigation solutions of outer loop, and the other part is given on the basis of the channel pre-filter outputs from inner loop. Each tacking channel has two filters of cascaded structure, one is the traditional pre-filter which is used to achieve GNSS signal tracking errors, and the second one is an extractor which is constructed to extract navigation solution derivation errors from the designed NCO controls and the signal tracking errors. For the ultra-tight integration navigation filter, the receiver clock residual error model after compensating the receiver clock drift is derived in detail. Finally, semi-physical simulation environment of the proposed ultra-tight integration scheme is built and closed-loop experiment under high dynamics scenario is put forward. The simulation results show that the proposed integration scheme can stably and robustly track the GNSS signals, and can achieve accurate navigation solutions even in harsh cases.

Performance Analysis of Adaptive Filter Channel Estimated MIMO OFDM Communication System

Advanced Communication Systems are wideband systems to support multiple applications such as audio, video and data so and so forth. These systems require high spectral efficiency and data rates. In addition, they should provide multipath fading and inter-symbol interference (ISI) free transmission. Multiple input multiple output orthogonal frequency division multiplexing (MIMO OFDM) meets these requirements Hence, MIMO-OFDM is the most preferable technique for long term evaluation advanced (LTE-A). The primary objective of this paper is to control bit error rate (BER) by proper channel coding, pilot carriers, adaptive filter channel estimation schemes and space time coding (STC). A combination of any of these schemes results in better BER performance over individual schemes. System performance is analyzed for various digital modulation schemes. In this paper,adaptive filter channel estimated MIMO OFDM system is proposed by integrating channel coding, adaptivefilter channel estimation, digital modulation and space time coding. From the simulation results, channel estimated 2×2 MIMO OFDM system shows superior performance over individual schemes.

Identifying Observables That Can Differentiate Between Impulsive and Footpoint Heating: Time Lags and Intensity Ratios

Abstract Observations of solar coronal loops have identified several common loop characteristics, including that loops appear to cool and have higher than expected densities. Two potential heating scenarios have been suggested to explain these observations. One scenario is that the loops are formed by many strands, each heated independently by a series of small-scale impulsive heating events, or nanoflares. Another hypothesis is that the heating is quasi-steady and highly stratified, i.e., “footpoint heating”; such heating can drive thermal nonequilibrium in some structures depending on the scale height and magnitude of the energy deposition, and the geometry of the structure. Studies of both types of heating have found that they can qualitatively reproduce the observed loop properties. The goal of this paper is to identify observables that can be used to differentiate between these two heating scenarios. To do this, we use a single loop geometry. For footpoint heating, we vary the heating magnitude and stratification, for impulsive heating, we vary the heating magnitude. We use one-dimensional hydrodynamic codes to calculate the resulting temperature and density evolution. We convolve the temperature and density with the response functions of four EUV channels of the Atmospheric Imaging Assembly and one filter channel of Hinode's X-ray Telescope. We consider two principal diagnostics: the time lag between the appearance of the loop in two different channels, and the ratio of the peak intensities of the loop in the two channels. Based on this limited data set, we find (1) that footpoint heating can predict longer time lags than impulsive heating in some channel pairs, (2) that footpoint heating can predict zero or negative time lags in some channel pairs, (3) that the intensity ratio expected from impulsive heating is confined to a narrow range, while footpoint heating predicts a wider range of intensity ratios, and (4) that the range of temperatures expected in impulsive heating is broader than the range of temperatures expected in footpoint heating. This preliminary study identifies observables that may be useful in discriminating between heating models in future work.

Negative Capacitance Effect in Ag/α-In2Se3/CdS/CdSe/C Dual Band Stop Filters

In the current study, a 1.5 μm thick three channel microwave band filter is designed and characterized. The thin film device which was constructed from the indium selenide, cadmium sulfide and cadmium selenide stacked dielectric materials sandwiched between silver and carbon films is studied by means of x-ray diffraction, energy dispersive x-ray analysis and impedance spectroscopy techniques. It was observed that the Ag thin film substrate induced the formation of the hexagonal α-In2Se3 phase of indium selenide. The x-ray analysis has also shown that the deposition of hexagonal CdS over Ag/α-In2Se3 and that of hexagonal CdSe over α-In2Se3/CdS under vacuum pressure of 10−8 bar is of a highly strained and mismatched physical nature. The impedance spectroscopy analysis in the frequency domain of 0.10–1.80 GHz has shown that; while the Ag/α-In2Se3/C channel exhibit negative capacitance (NC) effects in the frequency domain of 0.10–1.40 GHz, the Ag/α-In2Se3/CdS/C and the Ag/α-In2Se3/CdS/CdSe/C channels displayed a NC feature in the domains of 1.24–1.40 GHz and 1.10–1.56 GHz, respectively. The fitting of the capacitance spectra in accordance with the modified Ershov model allowed determining the NC and band filtering parameters. It was also observed that, although the Ag/α-In2Se3/C channel behaves as a high frequency low pass filter, the second and third channels displayed band stop filter features with notch frequencies of 1.38 GHz and 1.49 GHz, respectively. The features of the device nominate it for use as a parasitic capacitance canceller and as a three channels microwave filter.

Excitation energy transport with noise and disorder in a model of the selectivity filter of an ion channel

A selectivity filter is a gate in ion channels that is responsible for the selection and fast conduction of particular ions across the membrane (with high throughput rates of 108 ions s−1 and a high 1:104 discrimination rate between ions). It is made of four strands as the backbone, and each strand is composed of sequences of five amino acids connected by peptide units H–N–C=O in which the main molecules in the backbone that interact with ions in the filter are carbonyl (C=O) groups that mimic the transient interactions of ion with binding sites during ion conduction. It has been suggested that quantum coherence and possible emergence of resonances in the backbone carbonyl groups may play a role in mediating ion conduction and selectivity in the filter. Here, we investigate the influence of noise and disorder on the efficiency of excitation energy transfer (EET) in a linear harmonic chain of N = 5 sites with dipole–dipole couplings as a simple model for one P-loop strand of the selectivity filter backbone in biological ion channels. We include noise and disorder inherent in real biological systems by including spatial disorder in the chain, and random noise within a weak coupling quantum master equation approach. Our results show that disorder in the backbone considerably reduces EET, but the addition of noise helps to recover high EET for a wide range of system parameters. Our analysis may help for better understanding of the coordination of ions in the filter as well as the fast and efficient functioning of the selectivity filters in ion channels.

Personal Exposure to PM2.5 Black Carbon and Aerosol Oxidative Potential using an Automated Microenvironmental Aerosol Sampler (AMAS).

Traditional methods for measuring personal exposure to fine particulate matter (PM2.5) are cumbersome and lack spatiotemporal resolution; methods that are time-resolved are limited to a single species/component of PM. To address these limitations, we developed an automated microenvironmental aerosol sampler (AMAS), capable of resolving personal exposure by microenvironment. The AMAS is a wearable device that uses a GPS sensor algorithm in conjunction with a custom valve manifold to sample PM2.5 onto distinct filter channels to evaluate home, school, and other (e.g., outdoors, in transit, etc.) exposures. Pilot testing was conducted in Fresno, CA where 25 high-school participants ( n = 37 sampling events) wore an AMAS for 48-h periods in November 2016. Data from 20 (54%) of the 48-h samples collected by participants were deemed valid and the filters were analyzed for PM2.5 black carbon (BC) using light transmissometry and aerosol oxidative potential (OP) using the dithiothreitol (DTT) assay. The amount of inhaled PM2.5 was calculated for each microenvironment to evaluate the health risks associated with exposure. On average, the estimated amount of inhaled PM2.5 BC (μg day-1) and OP [(μM min-1) day-1] was greatest at home, owing to the proportion of time spent within that microenvironment. Validation of the AMAS demonstrated good relative precision (8.7% among collocated instruments) and a mean absolute error of 22% for BC and 33% for OP when compared to a traditional personal sampling instrument. This work demonstrates the feasibility of new technology designed to quantify personal exposure to PM2.5 species within distinct microenvironments.

Learning correlation filters in independent feature channels for robust visual tracking

Although existing correlation filter-based tracking algorithms have shown competitive performance, most of them suffer from defects of insufficient learning, inauthentic combination and inflexible update when it comes to multiple feature channels. To tackle these problems, a specific correlation filter is learned for each feature channel and then the final response map is generated according to the confidence of channels. The confidence is decided by both spatial and temporal distribution of response maps. Under such circumstances, correlation filters are allowed to be updated independently with their own learning rates which can vary with the diversification of feature space in corresponding channels. We evaluate our work on OTB-2013, OTB-2015 and VOT-2017. Our approach outperforms the baseline fDSST by 6.1% in Mean Overlap Precision (OP) especially on OTB-2015 and shows competitive performance compared to state-of-the-art trackers with hand-crafted features while running at 70 FPS.

Design of Ku‐band diplexer based on groove gap waveguide technology

A groove gap waveguide diplexer is presented for Ku-band applications. The manifest advantage of using this technology is its ability to remove requirement of electrical contact between the different layers of the structure. The proposed diplexer is composed of coupled gap waveguide resonators without additional waveguide elements. A prototype is fabricated and measured for experimental verification. The return losses of the channel filters of diplexer are higher than about 20 dB, in the desired frequency bands centered 14 and 15.5 GHz. A high degree of agreement between the measurements and simulations has been found.

Design of Three-State Diplexer Using a Planar Triple-Mode Resonator

A highly integrated three-state diplexer (TSD) on a single planar elliptical structure is for the first time presented in this paper. Three resonant modes are investigated in a planar elliptical resonator, e.g., two TM11 degenerate modes and one TM21 mode. These three resonant modes are designed to form three filtering channels, which are further combined to generate three states of a diplexer, namely, TSD. The planar elliptical triple-mode resonator is fed by three microstrip lines to form a triple-mode TSD. In order to validate the concept, the designed planar TSD is fabricated and measured. The measured results are in good agreement with the simulated ones.

Narrow-Band Add-Drop Filter Based on Phase-Modulated Grating-Assisted Contra-Directional Couplers

A narrow-band silicon photonic add-drop filter is demonstrated by using phase-modulated grating-assisted contra-directional couplers (contra-DCs) on the silicon-on-insulator platform. The apodization coupling is achieved by modulating the phase of one grating in a contra-DC, while keeping the other grating uniform. As the local effective index of the gratings remains almost unchanged, the designed apodized contra-DC has a large designing flexibility and a high sidelobe suppression ratio (SLSR). To obtain a narrow bandwidth, weak coupling is designed. Single-stage and dual-stage filtering are both studied. The experimental results show that single-stage filtering device has a 3-dB bandwidth of 0.9 nm and an SLSR of 18 dB. Dual-stage filtering device has a 3-dB bandwidth of 0.5 nm and an SLSR of 23 dB. Our devices are promising for on-chip applications that require narrow bandwidths such as wavelength-division-multiplexed channel filters.

Dual-Channel Dielectric Resonator Filter and Its Application to Doherty Power Amplifier for 5G Massive MIMO System

In this paper, a dual-channel dielectric resonator (DR) filter is presented for the first time. Two bandpass filters (BPFs) are integrated as one dual-channel filter with two input ports and two output ports. By using a common quad-mode DR shared by two second-order BPFs, only one metallic cavity is needed, which greatly reduces the circuit size. Frequency control of the DR is investigated and electromagnetic field properties at HEH11 and HEE11 resonant pairs are studied for guiding the dual-channel filter realization. By properly arranging the input and output feeding probes, two of the resonant modes are excited for one channel and other two for the other channel. Since the feeding probes of one channel filter do not excite the resonant modes of the other one, isolation between two filters is achieved. Three transmission zeros are generated near the passband, resulting in high selectivity. For verification, the dual-channel filter is implemented, which features good bandpass responses and offers a significant size reduction in comparison with conventional two DR filters. What is more, the dual-channel filter with the impedance transformation function is integrated with a $2 \times 2$ Doherty power amplifier for 5G massive multiple-input multiple-output system application, featuring high efficiency, good filtering responses, and high integration.

Calcium transport across plant membranes: mechanisms and functions

Contents Summary 49 I. Introduction 49 II. Physiological and structural characteristics of plant Ca2+ -permeable ion channels 50 III. Ca2+ extrusion systems 61 IV. Concluding remarks 64 Acknowledgements 64 References 64 SUMMARY: Calcium is an essential structural, metabolic and signalling element. The physiological functions of Ca2+ are enabled by its orchestrated transport across cell membranes, mediated by Ca2+ -permeable ion channels, Ca2+ -ATPases and Ca2+ /H+ exchangers. Bioinformatics analysis has not determined any Ca2+ -selective filters in plant ion channels, but electrophysiological tests do reveal Ca2+ conductances in plant membranes. The biophysical characteristics of plant Ca2+ conductances have been studied in detail and were recently complemented by molecular genetic approaches. Plant Ca2+ conductances are mediated by several families of ion channels, including cyclic nucleotide-gated channels (CNGCs), ionotropic glutamate receptors, two-pore channel 1 (TPC1), annexins and several types of mechanosensitive channels. Key Ca2+ -mediated reactions (e.g. sensing of temperature, gravity, touch and hormones, and cell elongation and guard cell closure) have now been associated with the activities of specific subunits from these families. Structural studies have demonstrated a unique selectivity filter in TPC1, which is passable for hydrated divalent cations. The hypothesis of a ROS-Ca2+ hub is discussed, linking Ca2+ transport to ROS generation. CNGC inactivation by cytosolic Ca2+ , leading to the termination of Ca2+ signals, is now mechanistically explained. The structure-function relationships of Ca2+ -ATPases and Ca2+ /H+ exchangers, and their regulation and physiological roles are analysed.

Novel Adaptive Filter Design for Filter Bank Multicarrier System Under Doubly Dispersive Channel Conditions

ABSTRACTFilter bank multicarrier (FBMC) has emerged as the favourite multicarrier communication technique since it meets the demands of the next-generation standards, especially for communication under doubly dispersive channels. In order to combat the undesirable channel effects like inter symbol interference and inter carrier interference, the prototype filters used in FBMC systems must satisfy orthogonality conditions and be well localized simultaneously in both time and frequency domains. Even though conventional doubly localized filters are optimum in the absence of channel, they fail to satisfy orthogonality and localization criteria under doubly dispersive channels. In the present study, an adaptive filter design method is proposed in which the prototype filter is designed as the weighted sum of a time-limited Nyquist filter, a band-limited Nyquist filter, and doubly localized Gaussian filter based on the analysis of discrete ambiguity function (DAF). The filter is designed to vary its characteristics according to the maximum time and frequency domain dispersions of the channel, so that signal-to-interference ratio is maximized. In order to ensure distortion-less transmission, the perfect reconstruction criterion for distortion-less transmission is mapped to specific conditions for DAF according to two-dimensional channel scattering function. The superiority in performance of the proposed adaptive filter is analysed in terms of signal-to-interference ratio and bit error rate, and is compared with the conventional filters for various channel scattering conditions.