Shaping Filter Research Articles

A Novel Shaping Scheme for PAPR Reduction in Single-Carrier Modulation

A novel PAPR shaping technique intended for systems with high spectral efficiency and single carrier transmission is presented. This technique applies puncturing of error correction redundancy bits to achieve a desired Markovian symbol transmission probability distribution, which avoids symbol sequences with high peak values. For a 16-QAM system with transmission rate of 3 bit/symbol and a root raised cosine (RRC) pulse shape filter with roll-off factor 0.1 and duration of six symbols, an overall gain of about 2.2 dB is demonstrated by simulations using pragmatic binary turbo code for error correction. The technique can be used to improve any single carrier communication link limited by the high power amplifier (HPA) peak power.

Reducing the risk of skin injuries in cardiac catheterization procedures: Optimization proposal for obese patients

PurposeDuring interventional cardiology procedures, high doses of X-ray may be delivered to patients. This is especially critical in cases of obese patients and/or high obliquity projections. High dose rates can then be produced in patients’ skin as well as insufficient image quality due to regulatory limitations in the X-ray tube output working in the fluoroscopy mode. In this paper, an optimization action is proposed to reduce patient entrance dose rate and preserve image quality in cases of thick patients. MethodsThe action is based on the evaluation of dose rate to the patient and image quality in a new fluoroscopy protocol with less frame rate (7.5 vs. 15 frames/s) and higher spectral shape filter (0.4 vs. 0.1 mm Cu). The new protocol is tested in an angiography room using a PMMA phantom and a test object. ResultsThe new fluoroscopy protocol (7.5 fr/s and 0.4 mm Cu) reduces entrance surface air kerma in 70%–10% (depending on PMMA thickness), preserving the incident air kerma per frame at the image detector. While at lower PMMA thickness, the MTF measured with bar pattern is better for the default protocol; at PMMA thickness between 32 and 37 cm, the optimized protocol produces better image quality indicators. ConclusionsThis work demonstrates that in the case of high thicknesses of PMMA (32–37 cm), increasing spectral beam filter and reducing frame rate may help improve image quality and maintain entrance surface air kerma so as to fulfil the regulatory requirements.

Social filters shaping student responses to teacher feedback in the secondary drama classroom

ABSTRACTLittle is known about how secondary drama students identify or utilise teacher feedback. This article presents findings from a study exploring how drama students describe their experiences of teacher feedback and how, or if, they apply this feedback to enhance their learning. Data collection and analysis focused on students’ experiences of teacher feedback occurring in three secondary drama classrooms in Queensland, Australia. Emergent findings suggest that drama students employ contextual, social and individual learning filters to assess the usefulness of teacher feedback. In the highly interactive and relational drama classroom, social filters can induce or hinder the existence of dialogic feedback. This can subsequently influence the drama students’ perspectives of the usefulness of teacher feedback. This article draws on the student voice to describe these social filters and suggests how drama teachers may culture opportunities for drama students to engage with dialogic and useful teacher feedback.

Implementation of real-time digital [formula omitted] shaping filter on FPGA for gamma-ray spectroscopy

A novel implementation of a digital CR–RCm shaping filter for gamma-ray spectroscopy is presented in this paper, derived from the digitalization and quantization of the input and output voltage of CR and RC circuits. Compared with the conventional digital CR–RCm shaper, it has a relatively simple structure consuming fewer multipliers and is easy to realize on DSP chips. More importantly, this digital shaper also overcomes the shortcoming of the conventional digital CR–RCm shaper, which lacks the function of pole-zero cancellation (PZC). Experimental data on noise suppression, immunity to ballistic deficit, and energy resolution improvement show that the digital spectroscopy system based on the described shaper achieves the same excellent performance as the analog spectroscopy system from CANBERRA, which therefore provides a new way to realize the shaping of digital signals from radiation detectors, and this carries great significance for engineering applications.

Preparation and Performance of Zirconia Fiber Board

Zirconia fiber not only can be used for a long time in 1600°C, but also has low thermal conductivity at high temperature. Due to the excellent insulation performance, it has a broad application prospect in aerospace, aviation, energy and other areas. In the present study, we chose yttrium stabilized zirconia fibers and nanometer zirconia powder as main material and adding soluble starch, zirconium sol as low temperature and high temperature binder. Rigid zirconia fiber board was prepared by material slurry, filter shaping, stripping drying and high temperature calcination. After high temperature calcination of 1600°C for 12h, sample pore are mainly concentrated in 25-75μm, bending strength performance is best when the adding amount of nanometer zirconia powder was 7%, the thermal conductivity is only 0.132 W·m-1·K-1 at 1400°C.

Influence of filter shape and bandwidth on noise-like pulse generation in all-normal-dispersion fiber lasers

We investigate theoretically the laser cavity design in a saturable absorber (SA) mode locked all-normal-dispersion fiber ring laser from which noise-like pulse (NLP) can be generated, highlighting the influence of the inserted filter shape and bandwidth. Theoretically we find that by using a high order super Gaussian profile filter and carefully choosing the filter bandwidth, pulse collapse and sub-pulses collision will happen. With certain choice of the filters in the cavity, we can achieve “L-shape” distribution of noise bursts with extreme peak power pulse, which indicates NLP emission fulfilling ORW criteria.

The MPSK and MQAM signal modulation recognition algorithm in the multipath channel

ABSTRACTThis paper proposes a new Lempel–Ziv complexity feature recognition algorithm based on the nth-powered () spectrum to deal with modulation recognition problem regarding MPSK and MQAM signals in multipath channels. Based on differences in the nth-powered () spectrum amplitude value of MPSK and MQAM signals, the waveform characteristics of the multiplied spectrum are extracted in the multipath environment, and a total of five characteristic parameters are defined to distinguish the signals from the set {BPSK,OQPSK,QPSK,8PSK,PI/4DQPSK,16QAM,32QAM}. The simulation results show that the recognition algorithm performs well when recognising signals in a multipath situation and is less affected by the frequency deviation and shaping filter coefficient; therefore, it is very robust.

Control systems design: the technology of stochastic perturbations simulation

An approach to the random perturbations simulation is considered for performing in the design of control systems for thermal power facilities. In order to take into account the stochastic nature of the technological processes, we proposed the simulation technique that allows us to superimpose random fluctuations on the deterministic model of the control system. To simulate random changes in process parameters, we synthesized the shaping filter that generates a random signal with the required autocovariance function. The developed technology allows us to adequately model the technological processes characterized by the action of random perturbations. This is especially important if the requirements for control quality are high. We have experimentally confirmed the suitability of the developed technology by performing control system simulation using MATLAB / Simulink.

Flicker Noise Simulation by Superposition of Normal Stationary Processes

The details of the well-known method for representing 1/f noise by a sum of stationary processes are presented. Two series of shaping filters are applied in the frequency band specified by the user. The relations for the filter parameters are determined. The error in the approximation of the spectrum is considered. An algorithm for modeling fluctuations in the form of a system of first-order stochastic difference equations is proposed. The algorithm is intended to be used in simulation models applied to study the errors of navigation systems.

Optimal iodine absorption line applied for spaceborne high spectral resolution lidar.

Spaceborne high spectral resolution lidar (HSRL) provides a wide range of observations, e.g., measurements of aerosol backscattering and extinction coefficients and aerosol depolarization ratio with high accuracy, which are of great significance to the study of air pollution monitoring and climate change. With different cells and finger temperatures, the transmittance of the different absorption lines of the iodine vapor filter at 532nm wavelength was measured. The 1064nm fundamental frequency pulse energy and the 532nm frequency-doubled pulse energy output of different seeder laser wavelengths were measured. Based on the relationship among the laser output power, the absorption line shape of the iodine vapor filter, and the atmospheric model, the echo power was calculated and compared. The 1110 iodine absorption line was selected as the optimized filter for the HSRL, which could increase in 22% and 14% efficiency compared with the traditional 1109 line, and a new proposed 1105 line at the 532nm HSRL channel at 5km altitude with an enhanced aerosol model, respectively.

Correction of seismic time-lapse data with different geometries

ABSTRACTIn the interpretation of time-lapse seismic data, we first assume that basal and monitor seismic data have been gathered and processed under equal condition. Basically having two sets of seismic data (basal and monitor data) does not confirm the possibility of 4D seismic data analysis and repeatability term commands that data should have equal data gathering and process condition. This is due to the low vertical resolution of seismic data which makes the changes in amplitude of seismic in basal and monitoring operations to occur finitely. Therefore, differences in amplitudes in two seismic surveys that have a source other than variations in reserval fluid saturation cause errors in 4D interpretations. In this paper, we represent a procedure to unify different geometries and also study post-stack processing methods for seismic time-lapse data and execute them on existing data at the studied field. In the, first step geometrical conception of basal and monitoring data should be equalized. This section has been implemented using a new methodology, developed in this paper and is called “similarity table”. Then, data will be analyzed with spectra point of view and by executing shaping filters and by using cross equalization approach, basal and monitor seismic information will be closer as far as possible. Finally, analyzes were performed to validate the obtained results and evaluate the quality of time -lapse seismic analyzes.

An improved time over threshold method using bipolar signals

The time over threshold (TOT) method has been recently proposed as a signal processing method used to calculate time and energy information by measuring the pulse arrival time and pulse duration over a preset threshold. Although TOT has been reported as an effective method for front end readout in PET applications, it has several limitations, including its non-linearity, lower dynamic range, and a trade-off between energy resolution and coincidence resolving time (CRT). In this study, we propose a novel design we developed to improve performance with regard to these problems occurring in the conventional TOT by employing a bipolar signal and two comparators. Using a high frequency CR shaping filter, a detected signal was converted into a bipolar signal, and the positive pulse of the converted bipolar signal had a fast rising time, while the negative pulse had a linear slope. The bipolar TOT circuit was composed of a preamplifier, a CR shaping filter, and two comparators. The PET detector was composed of a single LYSO coupled with 4 × 4 SiPM arrays, a bipolar TOT circuit, and an FPGA based TDC. And this was constructed to evaluate the performance of the proposed bipolar TOT method. A 16-ch PET detector module consisting of a 4 × 4 array LYSO coupled to a 4 × 4 SiPM arrays, an Anger logic discretized positioning circuit, and a 4-ch bipolar TOT circuit was also constructed to evaluate the functionality of the bipolar TOT method for PET applications. The pulse height resolution and CRT were measured using both the bipolar TOT method and the conventional TOT method. While the bipolar TOT method provided a similar pulse height resolution (10.4% ± 0.1%), the integral non-linearity (1.4%) and CRT (168 ± 4 ps) measured using the bipolar TOT method were greatly improved compared to those (17.2% and 258 ± 15 ps, respectively) measured with the conventional TOT method. The positions of the crystals were clearly identified, as seen in the flood histogram acquired using the 4-ch bipolar TOT circuit. The measured average pulse height resolution and average CRT for the 16-ch detector module were 11.5% ± 0.2% and 516 ± 24 ps. The results obtained in this study indicate that the bipolar TOT method requiring a relatively small number of electronic components could effectively improve the CRT, linearity and dynamic range. Furthermore, they also demonstrated the extendibility allowing the development of a PET system that consists of a large number of detectors.

Architecture optimization for energy-efficient resolution-scalable 8–12-bit SAR ADCs

Low power analog-to-digital converters (ADCs) in energy constrained devices, such as wireless sensor readout modules, often target dynamic resolution scalability with application context to reduce the average power consumption. This work implements such an 8–12-bit resolution scalable ADC, using an oversampling and noise-shaping successive approximating register (SAR) architecture. This architecture is selected for its high power efficiency after a detailed comparison of various resolution enhancing techniques within the SAR framework. Specifically, in this paper, three resolution enhancing techniques are reviewed and compared on their energy usage namely: the majority voting, the oversampling, and the oversampling with noise shaping SAR ADC. Furthermore, the proposed resolution scalable ADC simplifies the design of the noise shaping filter by enabling the use of a first order switched-capacitor low-pass filter for shaping the comparator noise and the in-band quantization noise. The ADC design also alleviates the matching concerns by using only an 8-bit capacitive digital-to-analog converter (DAC) for a maximum 12-bit resolution, or 11-bit effective number of bits (ENOB). The architecture can be configured to allow an operation from 8-bit traditional SAR ADC up to an 11-bit ADC by enabling the oversampling and noise shaping loops within the SAR architecture. This ADC is designed to operate with up to 320 kS/s and achieves a power scaling from 80 nW to 1.5 $$\upmu$$ W, resulting in an steeper energy-ENOB scaling trend compared to state-of-the art resolution scalable ADCs.

Environmental filters shaping angiosperm tree assembly along climatic and geographic gradients

AbstractQuestionGlobal‐scale forest censuses provide an opportunity to understand diversification processes in woody plant communities. Based on the climatic or geographic filtering hypotheses associated with tropical niche conservatism and dispersal limitation, we analysed phylogenetic community structures across a wide range of biomes and evaluated to what extent region‐specific processes have influenced large‐scale diversity patterns of tree species communities across latitude or continent.LocationGlobal.MethodsWe generated a data set of species abundances for 21,379 angiosperm woody plants in 843 plots worldwide. We calculated net relatedness index (NRI) for each plot, based on a single global species pool and regional species pools, and phylogenetic β‐diversity (PBD) between plots. Then, we explored the correlations of NRI with climatic and geographic variables, and clarified phylogenetic dissimilarity along geographic and climatic differences. We also compared these patterns for South America, Africa, the Indo‐Pacific, Australia, the Nearctic, Western Palearctic and Eastern Palearctic.ResultsNRI based on a global‐scale species pool was negatively associated with precipitation and positively associated with Quaternary temperature change. PBD was positively associated with geographic distance and precipitation difference between plots across tropical and extratropical biomes. Moreover, phylogenetic dissimilarity was smaller in extratropical regions than in regions including the tropics, although temperate forests of the Eastern Palearctic showed a greater dissimilarity within extratropical regions.ConclusionsOur findings support predictions of the climatic and geographic filtering hypotheses. Climatic filtering (climatic harshness and paleoclimatic change) relative to tropical niche conservatism played a role in sorting species from the global species pool and shaped the large‐scale diversity patterns, such as the latitudinal gradient observed across continents. Geographic filtering associated with dispersal limitation substantially contributed to regional divergence of tropical/extratropical biomes among continents. Old, long‐standing geographic barriers and recent climatic events differently influenced evolutionary diversification of angiosperm tree communities in tropical and extratropical biomes.

A photon source model based on particle transport in a parameterized accelerator structure for Monte Carlo dose calculations.

An accurate source model of a medical linear accelerator is essential for Monte Carlo (MC) dose calculations. This study aims to propose an analytical photon source model based on particle transport in parameterized accelerator structures, focusing on a more realistic determination of linac photon spectra compared to existing approaches. We designed the primary and secondary photon sources based on the photons attenuated and scattered by a parameterized flattening filter. The primary photons were derived by attenuating bremsstrahlung photons based on the path length in the filter. Conversely, the secondary photons were derived from the decrement of the primary photons in the attenuation process. This design facilitates these sources to share the free parameters of the filter shape and be related to each other through the photon interaction in the filter. We introduced two other parameters of the primary photon source to describe the particle fluence in penumbral regions. All the parameters are optimized based on calculated dose curves in water using the pencil-beam-based algorithm. To verify the modeling accuracy, we compared the proposed model with the phase space data (PSD) of the Varian TrueBeam 6 and 15MV accelerators in terms of the beam characteristics and the dose distributions. The EGS5 Monte Carlo code was used to calculate the dose distributions associated with the optimized model and reference PSD in a homogeneous water phantom and a heterogeneous lung phantom. We calculated the percentage of points passing 1D and 2D gamma analysis with 1%/1mm criteria for the dose curves and lateral dose distributions, respectively. The optimized model accurately reproduced the spectral curves of the reference PSD both on- and off-axis. The depth dose and lateral dose profiles of the optimized model also showed good agreement with those of the reference PSD. The passing rates of the 1D gamma analysis with 1%/1mm criteria between the model and PSD were 100% for 4×4, 10×10, and 20×20cm2 fields at multiple depths. For the 2D dose distributions calculated in the heterogeneous lung phantom, the 2D gamma pass rate was 100% for 6 and 15MV beams. The model optimization time was less than 4min. The proposed source model optimization process accurately produces photon fluence spectra from a linac using valid physical properties, without detailed knowledge of the geometry of the linac head, and with minimal optimization time.

Design Methodology of N-Path Filters With Adjustable Frequency, Bandwidth, and Filter Shape

In this paper, an adaptive N-path filter design technique is presented. The filter designed by this method can be reconfigured to different shapes, e.g., Butterworth or Chebyshev with variable bandwidth (BW), based on the user requirements. In addition, an analytical synthesis procedure is introduced to realize high-order bandpass filters (BPFs) based on N-path architecture with a prescribed set of specifications. A proof-of-concept BPF is fabricated and measured in a 65-nm CMOS process. The filter can be reconfigured to realize different filter shapes by changing coupling capacitors. The BW of the proposed filter is also tunable. The passband of the filter is tunable from 0.2 to 1.2 GHz with a gain of 14.5–18 dB, a noise figure of 3.7–5.5 dB, and a total power consumption of 37.5–52.7 mW. The channel BW can be varied from 20 to 40 MHz and the filter out-of-band third-order intercept point ( $\Delta f=50$ MHz) is 25 dBm.

Mach-Zehnder crossbar switching and tunable filtering using N-coupled waveguide Bragg resonators.

This theoretical modeling-and-simulation paper presents designs and projected performance of ~1500-nm silicon-on-insulator 2 x 2 Mach-Zehnder interferometer (MZI) optical crossbar switches and tunable filters that are actuated by thermo-optical (TO) means. A TO heater stripe is assumed to be on the top of each waveguided arm in the interferometer. Each strip-waveguide arm contains an inline set of N-fold coupled, phase-shifted Bragg-grating resonators. To implement accurate and realistic designs, a mixed full-vectorial mathematical model based upon the finite-element, coupled-mode, and transfer-matrix approaches was employed. The Butterworth-filter technique for grating length and weighting was used. The resulting narrowband waveguide-transmission spectral shape was better-than-Lorentzian because of its steeper sidewalls (faster rolloff). The metrics of crossbar switching, insertion loss (IL) and crosstalk (CT), were evaluated for choices of grating strength and TO-induced change in the grating-waveguide refractive index. The predicted ILs and CTs were quite superior to those cited in the literature for experimental and theoretical MZI devices based upon silicon nanobeam resonators. This was true for the Type-I and Type-II resonator addressing discussed here. Finally, we examined the TO-tunable composite filter profiles that are feasible by connecting two or more Type-I MZIs in an optical series arrangement. A variety of narrow filter shapes, tunable over ~2 nm, was found.

Tunable Single-Passband Microwave Photonic Filter Based on Integrated Optical Double Notch Filter

A novel-integration-based technique employing a cascaded pair of microring resonators on silicon-on-insulator platform that can achieve a tunable single-passband microwave photonic filter with improved shape factor and extinction ratio is presented. It is based on an integrated optical double notch filter using a cascaded pair of nonidentical microring resonators, in conjunction with optical phase modulation. This results in minimal net phase being introduced by the overall filter at radio frequencies falling outside the region of the notch stopband, thus enabling nearly full antiphase cancellation of the modulation sidebands, which results in the achievement of an improved filter shape factor and extinction ratio. Additionally, it features a bandwidth that is directly determined by the difference between the bandwidths of the two optical notch filters, rather than by their absolute individual bandwidths. Experimental results have verified the concept, and have demonstrated a single-passband filter having tuning range of 6–17 GHz, a shape factor of 1.78, shape-invariant tuning, and a good out-of-band suppression ratio of approximately 20 dB throughout the entire tuning range.

A CMOS 6–10 GHz impulse radio UWB transmitter based on gated oscillator with switching pulse shaper

In an impulse radio ultra-wideband (IR-UWB) system for low-power location-aware sensor networks, the output pulses must meet the FCC spectral emission mask. In addition, to increase battery life, the IR-UWB transmitter must be energy efficient. In this paper, a CMOS ultra-wideband (UWB) transmitter designed using a 0.11-μm process is presented for 6–10 GHz applications. To reduce energy consumption, the transmitter adopts a gated voltage-controlled oscillator (VCO) that directly drives 50 Ω output impedance. A gated VCO that uses a trapezoidal pulse for on/off gating of the tail current source satisfies the spectrum mask without requiring an additional pulse shaping filter. The active energy consumption is 13.4 pJ/pulse at a pulse repeating frequency (PRF) of 40 MHz. The side-lobe rejection performance is more than 30 dB.

Laboratory investigations for development of design criteria for varying shapes of protective filters

Laboratory investigations have been carried out in the past regarding the design of protective filters based on the controlling constriction size of the filter mass. In all such studies, the particle shape has been considered spherical. However the fact remains, that the controlling constriction size changes with shape of filter particles. The present study is an attempt to assess the effect of shape on controlling constriction size usually based on the concept of spherical shape, and subsequently observe its effect on the design criteria adopted for filters. Based on laboratory investigations for three different shapes of filter material i.e. elliptical, sub-rounded and irregular, the improvements to the existing filter design criterion are proposed in this study by way of correction factors for each shape of filter material.