scholarly journals Broadband Spectral Analysis Algorithm with High-Frequency Resolution for Elimination of Overlap Interference between Adjacent Channels

2021 ◽  
Vol 11 (21) ◽  
pp. 10262
Author(s):  
Xianhai Wang ◽  
Teng Wang ◽  
Chuan Yin ◽  
Jun Han ◽  
Qiao Meng ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
High Frequency ◽  
Filter Bank ◽  
Large Scale ◽  
Spectral Lines ◽  
Frequency Resolution ◽  
Output Data ◽  
Wideband Signals ◽  
Flexible Architecture ◽  
Adjacent Channels

Spectral lines can be analysed to determine the physical properties of molecular clouds and the astrochemical processes in the formation area of massive stars. To improve the observation technology of radio astronomy, this paper proposes and compares two spectral analysis algorithms (improved weighted overlap-add (IWOLA) + FFT and IWOLA + weighted overlap-add (WOLA)). The proposed algorithms can obtain an ultra-high-frequency resolution for real-valued wideband signals, eliminate the signal overlapping interference between adjacent channels, substantially decrease the required hardware resources, especially multipliers, adders, and memory resources, and reduce the system design complexity. The IWOLA + FFT algorithm consists of an improved weighted overlap-add (IWOLA) filter bank, fast Fourier transform (FFT), a specific decimation for the output data from the IWOLA filter bank, and a selection for part of the output data from the FFT. The IWOLA + WOLA algorithm consists of the same modules as the IWOLA + FFT algorithm, with the second-stage FFT replaced by the modules of the weighted overlap-add (WOLA) filter bank and the accumulation for each sub-band. Based on an analysis of the underlying principles and characteristics of both algorithms, the IWOLA + FFT algorithm demonstrated a spectrum with a high frequency resolution and a comparable performance to an ultra-large-scale FFT, based on two smaller FFTs and a flexible architecture instead of a ultra-large-scale FFT. The IWOLA + WOLA algorithm contains the same function as the IWOLA + FFT algorithm and demonstrates a higher performance. The proposed algorithms eliminated the interference between the adjacent channels within the entire Nyquist frequency bandwidth. The simulation results verify the accuracy and spectral analysis performances of the proposed algorithms.

scholarly journals High Frequency Modal Testing of the Multiblade Packets Using a Noncontact Measurement and Excitation System

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
C. H. Liu ◽  
C. Zang ◽  
F. Li ◽  
E. P. Petrov
Keyword(s):  
High Frequency ◽  
Measurement Method ◽  
Natural Frequencies ◽  
Spectral Lines ◽  
Modal Testing ◽  
Frequency Resolution ◽  
Mode Shapes ◽  
Finite Model ◽  
Frequency Range ◽  
Noncontact Measurement

High cycle failure of blades and vanes caused by the vibration is one of the major causes reducing the lifetime of turbomachines. For multiblade packets, the failure may occur at vibrations with high frequencies that can reach up to tens of kHz. The experimental modal testing of blades is crucial for the validation of numerical models and for the optimization of turbomachine design. In this paper, the test rig and procedure for measurements of dynamic characteristics of lightweight multiblade packets in wide and high frequency ranges are developed. The measurements are based on a noncontact excitation and noncontact measurement method, which allows the determination of the modal characteristics of the packets with high accuracy in wide frequency ranges. The responses of the multiblade packets are measured using a Scanning Laser Doppler Vibrometry (SLDV), while vibrations are excited by the acoustic excitation technique. Modal tests of the blade packet comprising 18 vane blades connected by shrouds are performed. The measurements are performed within the high frequency range of 0–30 kHz, and the natural frequencies and mode shapes are obtained for first 97 modes. To capture the complex high frequency blade mode shapes, each blade in the packet is scanned over 25 reference points uniformly distributed over the blade concave surface. In order to obtain the high frequency resolution, the frequency range used for the measurements is split into several frequency intervals accordingly to the number of spectral lines available in the used data acquisition system, and for each such interval, the test is performed separately. The finite model of the packet is created, and the numerical modal analysis is performed to compare the calculated natural frequencies and mode shapes with the experimental measurements. The comparison shows the satisfactory with those from finite element analysis. It illustrates the measurement method described in this work is effective and reliable.

scholarly journals HEROS Be Star Campaigns

2000 ◽  
Vol 175 ◽  
pp. 356-363 ◽  
Author(s):  
S. Štefl ◽  
T. Rivinius
Keyword(s):  
High Frequency ◽  
Spectroscopic Data ◽  
Spectral Lines ◽  
Frequency Resolution ◽  
High Spectral Resolution ◽  
Data Sets ◽  
Strong Impact ◽  
Be Stars ◽  
Be Star ◽  
Different Parts

AbstractSystematic Be star observations with the HEROS spectrograph have been carried out in several long observing runs and seasons, mainly at the ESO La Silla Observatory. The HEROS data represents one of the most extended spectroscopic data sets for the Be star research. More complete and efficient diagnostics and a higher frequency resolution in analyses of periodic spectral variations were achieved, thanks to a combination of relatively high spectral resolution, a large sample of monitored spectral lines of different formation properties, long observing runs, and a relatively high frequency of observations of main targets.Important results concerning different parts of the extended atmospheres of Be stars and having strong impact on our understanding of these objects have been achieved.

scholarly journals Spectral analysis of discrete signals with high frequency resolution

2019 ◽  
pp. 270-282
Author(s):  
О.В. Осипов
Keyword(s):  
Spectral Analysis ◽  
High Frequency ◽  
Time Complexity ◽  
Fourier Transforms ◽  
Electronic Devices ◽  
Digital Signal ◽  
Frequency Resolution ◽  
Frequency Responses ◽  
Discrete Signals ◽  
To Receive

Представлены алгоритмы прямого и обратного быстрого преобразований Фурье (БПФ), позволяющие обрабатывать дискретные сигналы с высоким частотным разрешением, в том числе с небольшим количеством отсчетов получать амплитудночастотные характеристики с длиной набора частот, большей, чем длина исходного дискретного сигнала. Временная сложность разработанных алгоритмов для прямого и обратного БПФ равна O(N R log2 N), где R частотное разрешение спектральной характеристики (отношение длины набора частот к длине N набора отсчетов сигнала). Разработанные методы позволят увеличить разрешающую способность отечественных систем цифровой обработки сигналов и могут быть реализованы в электронике и программном обеспечении для спектрального анализа. Algorithms of direct and inverse fast Fourier transforms are discussed. These algorithms allow one to process discrete signals with high frequency resolution, including with a small number of frequency samples, and to receive the frequency responses with a set length of frequencies greater than the length of the original discrete signal. The time complexity of the developed algorithms for the direct and inverse FFT is O(N R log2 N), where R is the frequency resolution of the spectral characteristic (the ratio of the length of a set of frequencies to the length N of a set of signal samples). The developed methods allow one to increase the resolution of systems of digital signal processing and can be implemented in electronic devices and in software for spectral analysis.

scholarly journals Spectral Analysis of Stationary Signals Based on Two Simplified Arrangements of Chirp Transform Spectrometer

Electronics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 65
Author(s):  
Quan Zhao ◽  
Ling Tong ◽  
Bo Gao
Keyword(s):  
Spectral Analysis ◽  
Frequency Conversion ◽  
Frequency Resolution ◽  
Matching Problem ◽  
System Sensitivity ◽  
Deep Space Exploration ◽  
Spectrum Measurement ◽  
Stationary Signals ◽  
Simulation And Experiment ◽  
Remote Sensing Systems

The classical two-channel push-pull chirp transform spectrometer (CTS) has been widely applied in satellite-borne remote sensing systems for earth observation and deep space exploration. In this paper, we present two simplified structures with single M(l)-C(s) CTS arrangements for the spectral analysis of stationary signals. A simplified CTS system with a single M(l)-C(s) arrangement and a time delay line was firstly developed. Another simplified structure of CTS with a M(l)-C(s) arrangement and a frequency conversion channel was also developed for spectral analysis of stationary signals. Simulation and experiment results demonstrate that the two simplified arrangements can both realize spectrum measurement for the stationary signals and obtain the same frequency resolution, amplitude accuracy and system sensitivity as that of the classical two-channel push–pull CTS system. Compared to the classical CTS structure, the two simplified arrangements require fewer devices, save power consumption and have reduced mass. The matching problem between the two channels can be avoided in the two simplified arrangements. The simplified CTS arrangements may have potential application in the spectrum measurement of stationary signals in the field of aviation and spaceflight.

scholarly journals Evaluation of working memory in relation to cochlear implant consonant speech discrimination

2021 ◽  
Vol 37 (1) ◽  
Author(s):  
Mai M. El Ghazaly ◽  
Mona I. Mourad ◽  
Nesrine H. Hamouda ◽  
Mohamed A. Talaat
Keyword(s):  
Working Memory ◽  
Speech Perception ◽  
High Frequency ◽  
Word List ◽  
Frequency Discrimination ◽  
Frequency Resolution ◽  
Speech Discrimination ◽  
Place Of Articulation ◽  
Strong Positive Relationship ◽  
Speech And Language Development

Abstract Background Speech perception in cochlear implants (CI) is affected by frequency resolution, exposure time, and working memory. Frequency discrimination is especially difficult in CI. Working memory is important for speech and language development and is expected to contribute to the vast variability in CI speech reception and expression outcome. The aim of this study is to evaluate CI patients’ consonants discrimination that varies in voicing, manner, and place of articulation imparting differences in pitch, time, and intensity, and also to evaluate working memory status and its possible effect on consonant discrimination. Results Fifty-five CI patients were included in this study. Their aided thresholds were less than 40 dBHL. Consonant speech discrimination was assessed using Arabic consonant discrimination words. Working memory was assessed using Test of Memory and Learning-2 (TOMAL-2). Subjects were divided according to the onset of hearing loss into prelingual children and postlingual adults and teenagers. Consonant classes studied were fricatives, stops, nasals, and laterals. Performance on the high frequency CVC words was 64.23% ± 17.41 for prelinguals and 61.70% ± 14.47 for postlinguals. These scores were significantly lower than scores on phonetically balanced word list (PBWL) of 79.94% ± 12.69 for prelinguals and 80.80% ± 11.36 for postlinguals. The lowest scores were for the fricatives. Working memory scores were strongly and positively correlated with speech discrimination scores. Conclusions Consonant discrimination using high frequency weighted words can provide a realistic tool for assessment of CI speech perception. Working memory skills showed a strong positive relationship with speech discrimination abilities in CI.

scholarly journals Optimizing the Frequency Capping: A Robust and Reliable Methodology to Define the Number of Ads to Maximize ROAS

2021 ◽  
Vol 11 (15) ◽  
pp. 6688
Author(s):  
Jesús Romero Leguina ◽  
Ángel Cuevas Rumin ◽  
Rubén Cuevas Rumin
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
Low Frequency ◽  
Digital Marketing ◽  
Optimal Frequency ◽  
Novel Technique ◽  
Maximum Threshold

The goal of digital marketing is to connect advertisers with users that are interested in their products. This means serving ads to users, and it could lead to a user receiving hundreds of impressions of the same ad. Consequently, advertisers can define a maximum threshold to the number of impressions a user can receive, referred to as Frequency Cap. However, low frequency caps mean many users are not engaging with the advertiser. By contrast, with high frequency caps, users may receive many ads leading to annoyance and wasting budget. We build a robust and reliable methodology to define the number of ads that should be delivered to different users to maximize the ROAS and reduce the possibility that users get annoyed with the ads’ brand. The methodology uses a novel technique to find the optimal frequency capping based on the number of non-clicked impressions rather than the traditional number of received impressions. This methodology is validated using simulations and large-scale datasets obtained from real ad campaigns data. To sum up, our work proves that it is feasible to address the frequency capping optimization as a business problem, and we provide a framework that can be used to configure efficient frequency capping values.

High Frequency Vibration Analysis of Automotive Body Panels with Damping Materials

2010 ◽  
Vol 36 ◽  
pp. 293-296
Author(s):  
Yoshio Kurosawa ◽  
Takao Yamaguchi
Keyword(s):  
High Frequency ◽  
Large Scale ◽  
The Body ◽  
Viscoelastic Damping ◽  
Fe Model ◽  
Test Results ◽  
Automotive Body ◽  
Modal Damping ◽  
Practical Tool ◽  
Damping Materials

We have developed a technique for estimating vibrations of an automotive body structures with viscoelastic damping materials using large-scale finite element (FE) model, which will enable us to grasp and to reduce high-frequency road noise（200～500Hz）. In the new technique, first order solutions for modal loss factors are derived applying asymptotic method. This method saves calculation time to estimate modal damping as a practical tool in the design stages of the body structures. Frequency responses were calculated using this technique and the results almost agreed with the test results. This technique can show the effect of the viscoelastic damping materials on the automotive body panels, and it enables the more efficient layout of the viscoelastic damping materials. Further, we clarified damping properties of the automotive body structures under coupled vibration between frames and panels with the viscoelastic damping materials.

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