Spatial Repetitive Controller based Harmonic Mitigation Methodology For Wide Varying Base Frequency Range

2019 ◽  
Author(s):  
Hao Zeng ◽  
Robert D. Lorenz ◽  
Christoph H. van der Broeck ◽  
Rik W. De Doncker
Keyword(s):  
Frequency Range ◽  
Base Frequency ◽  
Harmonic Mitigation ◽  
Repetitive Controller

scholarly journals Interpretation of Cluster WBD frequency conversion mode data

2013 ◽  
Vol 3 (2) ◽  
pp. 547-565
Author(s):  
J. S. Pickett ◽  
I. W. Christopher ◽  
D. L. Kirchner
Keyword(s):  
Time Scale ◽  
Frequency Conversion ◽  
Wave Packets ◽  
High Time Resolution ◽  
Frequency Range ◽  
Waveform Data ◽  
Filter Bandwidth ◽  
Base Frequency ◽  
Impulsive Wave ◽  
Down Conversion

Abstract. The Cluster Wide-Band Data (WBD) plasma wave receiver mounted on each of the four Cluster spacecraft obtains high time resolution waveform data in the frequency range of ~70 Hz to 577 kHz. In order to make measurements above 77 kHz, it uses frequency conversion to sample the higher frequency waves at one of three different conversion frequencies (~125, 250 and 500 kHz, where these frequencies are the base frequency of the frequency range being sampled) in one of three different filter bandwidths (9.5, 19 and 77 kHz). Within the WBD instrument a down conversion technique, built around quadrature mixing, is used to convert these data to baseband (0 kHz) in order to reduce the sample rate for telemetry to the ground. We describe this down conversion technique and illustrate it through data obtained in space. Because these down converted data sometimes contain pulses, which can be indicative of nonlinear physical structures (e.g., electron phase space holes and electron density enhancements and depletions), it is necessary to understand what effects mixing and down conversion have on them. We present simulations using constructed signals containing pulses, nonlinear wave packets, sinusoids and noise. We show that the pulses and impulsive wave packets, if of sufficient amplitude and of appropriate width, survive the down conversion process, sometimes with the same pulse shape but usually with reduced amplitude, and have time scales consistent with the filter bandwidth at the base frequency. Although we cannot infer the actual time scale of the pulses and impulsive wave packets as originally recorded by the WBD instrument before mixing and down conversion, their presence indicates nonlinear processes occurring at or somewhat near the location of the measurement. Sinusoidal waves are represented in the down conversion time scale as sinusoids of nearly the same amplitude and at frequencies adjusted down by the conversion frequency. The original input waveforms, regardless of their shape, whether pulses or sinusoids, can never be recovered from the down converted waveforms.

scholarly journals Interpretation of Cluster WBD frequency conversion mode data

2014 ◽  
Vol 3 (1) ◽  
pp. 21-27 ◽  
Author(s):  
J. S. Pickett ◽  
I. W. Christopher ◽  
D. L. Kirchner
Keyword(s):  
Frequency Conversion ◽  
Wave Packets ◽  
Wide Band ◽  
High Time Resolution ◽  
Frequency Range ◽  
Waveform Data ◽  
Filter Bandwidth ◽  
Base Frequency ◽  
Impulsive Wave ◽  
Down Conversion

Abstract. The Cluster wide-band data (WBD) plasma wave receiver mounted on each of the four Cluster spacecraft obtains high time resolution waveform data in the frequency range of ~70 Hz to 577 kHz. In order to make measurements above 77 kHz, it uses frequency conversion to sample the higher frequency waves at one of three different conversion frequencies (~125, 250 and 500 kHz, these frequencies being the possible options for setting the base frequency of the frequency range being sampled) in one of three different filter bandwidths (9.5, 19 and 77 kHz). Within the WBD instrument, a down-conversion technique, built around quadrature mixing, is used to convert these data to baseband (0 kHz) in order to reduce the sample rate for telemetry to the ground. We describe this down-conversion technique and illustrate it through data obtained in space. Because these down-converted data sometimes contain pulses, which can be indicative of nonlinear physical structures (e.g., electron phase-space holes and electron density enhancements and depletions), it is necessary to understand what effects mixing and down conversion have on them. We present simulations using constructed signals containing pulses, nonlinear wave packets, sinusoids and noise. We show that the pulses and impulsive wave packets, if of sufficient amplitude and of appropriate width, survive the down-conversion process, sometimes with the same pulse shape but usually with reduced amplitude, and have timescales consistent with the filter bandwidth at the base frequency. Although we cannot infer the actual timescale of the pulses and impulsive wave packets as originally recorded by the WBD instrument before mixing and down conversion, their presence indicates nonlinear processes occurring at or somewhat near the location of the measurement. Sinusoidal waves are represented in the down-conversion timescale as sinusoids of nearly the same amplitude and at frequencies adjusted down by the conversion frequency. The original input waveforms, regardless of their shape, whether pulses or sinusoids, can never be recovered from the down-converted waveforms.

Density-based discrimination of protein and RNA in the ribosome

1992 ◽  
Vol 50 (1) ◽  
pp. 464-465
Author(s):  
Joachim Frank
Keyword(s):  
Transfer Function ◽  
Spatial Frequency ◽  
Three Dimensional ◽  
Wiener Filter ◽  
Dark Field Image ◽  
Dark Field ◽  
Frequency Range ◽  
Bright Field ◽  
Contrast Transfer Function ◽  
Pass Filter

Cryo-electron microscopy combined with single-particle reconstruction techniques has allowed us to form a three-dimensional image of the Escherichia coli ribosome.In the interior, we observe strong density variations which may be attributed to the difference in scattering density between ribosomal RNA (rRNA) and protein. This identification can only be tentative, and lacks quantitation at this stage, because of the nature of image formation by bright field phase contrast. Apart from limiting the resolution, the contrast transfer function acts as a high-pass filter which produces edge enhancement effects that can explain at least part of the observed variations. As a step toward a more quantitative analysis, it is necessary to correct the transfer function in the low-spatial-frequency range. Unfortunately, it is in that range where Fourier components unrelated to elastic bright-field imaging are found, and a Wiener-filter type restoration would lead to incorrect results. Depending upon the thickness of the ice layer, a varying contribution to the Fourier components in the low-spatial-frequency range originates from an “inelastic dark field” image. The only prospect to obtain quantitatively interpretable images (i.e., which would allow discrimination between rRNA and protein by application of a density threshold set to the average RNA scattering density may therefore lie in the use of energy-filtering microscopes.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

The influence of external conditions on sound pressure in the pistonphone at the infrasound frequency range

2020 ◽  
pp. 67-72
Author(s):  
A. V. Konkov ◽  
D. V. Golovin
Keyword(s):  
Environmental Conditions ◽  
Sound Pressure ◽  
Primary Method ◽  
Frequency Range ◽  
External Conditions ◽  
Numerical Estimations

The influence of environmental conditions on a sound pressure reproduced by the primary method in the measuring chambers of the Pistonphone in the frequency range from 1 mHz to 250 Hz is estimated. Numerical estimations of influence of environmental conditions on sound pressure in pistonphone measuring chambers are given and special requirements to system of maintenance of required external conditions are specified.

The working standard of the unit of power of electromagnetic waves in the frequency range from 37,5 to 220 GHz

2020 ◽  
pp. 53-58
Author(s):  
A. V. Koudelny ◽  
I. M. Malay ◽  
V. A. Perepelkin ◽  
I. P. Chirkov
Keyword(s):  
Microwave Power ◽  
Electromagnetic Waves ◽  
Primary Standard ◽  
The State ◽  
Frequency Range ◽  
Working Standard ◽  
Extended Frequency Range ◽  
Effective Efficiency ◽  
Extended Frequency ◽  
Good Agreement

The possibility of using bolometric converters of microwave power from the State primary standard of the unit of power of electromagnetic waves in waveguide and coaxial paths GET 167-2017, which has a frequency range from 37,5 to 78,33 GHz, in an extended frequency range up to 220 GHz, is shown. Studies of semiconductor bolometric converters of microwave power in an extended frequency range have confirmed good agreement and smooth frequency characteristics of the effective efficiency factor of the converters. Based on the research results, the State working standard of the unit of power of electromagnetic waves of 0,1–10 mW in the frequency range from 37,5 to 220 GHz 3.1.ZZT.0288.2018 was approved. The technical characteristics of the working standard of the unit of power of electromagnetic oscillations in an extended frequency range from 37,5 to 220 GHz are given.

Portable Bioimpedance Spectrometer for Total Frequency Range of β-Dispersion

2013 ◽  
Vol 80 (11) ◽  
Author(s):  
Dhouha Bouchaala ◽  
Olfa Kanoun ◽  
Nabil Derbel
Keyword(s):  
Frequency Range ◽  
Total Frequency
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