Method for Reducing the Amplitude Error of the Magnetic Comparator

Выходные сигналы датчиков при контроле ферромагнитных материалов методом эффекта Баркгаузена (метод неразрушающего контроля, основанный на регистрации параметров cкачков намагниченности, возникающих в результате эффекта Баркгаузена) представляют собой поток импульсов ЭДС от скачков Баркгаузена. Он имеет статистический характер (так называемый магнитный шум). При большом их количестве за полуцикл перемагничивания осуществляют либо скользящее усреднение, либо за весь полуцикл.В бистабильных ферромагнетиках флуктуации выходных сигналов датчика (а последние представляют два импульса разной полярности за цикл перемагничивания) не могут быть усреднены без потери информации, что снижает метрологические характеристики всего устройства. Флуктуируют такие параметры, как амплитуда, длительность, поле старта. Это ограничивает применение его в точных измерениях.Для разработки способа повышения стабильности выходного сигнала датчика использована гипотеза о полном переключении объема бистабильного образца ферромагнитного материала при скачке Баркгаузена. Гипотеза основана на новых физических данных, полученных при исследовании бистабильных ферромагнетиков авторами С. А. Барановым, Г. В. Ломаевым, С. П. Ахизиной, Г. В. Каримовой и другими.Предложен способ уменьшения флуктуаций амплитуды импульса ЭДС на выходе магнитного компаратора, заключающийся в преобразовании вольт-секундной площади в импульс, пропорциональный амплитуде. Разработана простая и надежная схема, реализующая данный способ. Проведена серия экспериментов. Показано, что флуктуация выходного сигнала уменьшается при использовании разработанного способа почти на порядок.Апробация способа осуществлялась на сердечниках из сплава викаллой 2 (Co52Fe38V10), подвергнутых крутильной деформации до предела текучести по технологии, разработанной на кафедре «Приборы и методы измерения, контроля и диагностики» ИжГТУ имени М. Т. Калашникова.

A 5-bit X-band GaN HEMT-Based Phase Shifter

In this study, we propose a 5-bit X-band gallium nitride (GaN) high electron mobility transistor (HEMT)-based phased shifter monolithic microwave integrated circuit for a phased-array technique. The design includes high-pass/low-pass networks for the 180° phase bit, two high-pass/bandpass networks separated for the 45° and 90° phase bits, and two transmission lines based on traveling wave switch and capacitive load networks that are separated for the 11.25° and 22.5° phase bits. The state-to-state variation in the insertion loss is 11.8 ± 3.45 dB, and an input/output return loss of less than 8 dB was obtained in a frequency range of 8–12 GHz. Moreover, the phase shifter achieved a low root mean square (RMS) phase error and RMS amplitude error of 6.23° and 1.15 dB, respectively, under the same frequency range. The measured input-referred P1dB of the five primary phase shift states were larger than 29 dBm at 8 GHz. The RMS phase error and RMS amplitude error slightly increased when the temperature increased from 25 to 100 °C. The on-chip phase shifter exhibited no dc power consumption and occupied an area of 2 × 3 mm2.

Observation impact study of an Arctic cyclone associated with a Tropopause Polar Vortex (TPV)-induced Rossby wave initiation event

A case study characterized by Arctic cyclogenesis following a tropopause polar vortex (TPV)-induced Rossby wave initiation event is used to better understand how well existing observations constrain analyses of processes influencing Arctic cyclone predictive skill. Complementary techniques of observation system experiments (OSE) and ensemble sensitivity analysis (ESA) are used to investigate the impacts of existing observation networks on predictions for this case. The ESA reveals that the large-scale Rossby wave structure correlated with both Arctic cyclone track and amplitude errors. The ensemble analyses of mid-level moisture in the warm conveyor belt region were correlated with forecast cyclone amplitude, but this feature was poorly sampled in existing observations. There is also a sensitivity of Arctic cyclone forecast amplitude error to low level temperature in the air mass of the cyclogenesis region at analysis time and a sensitivity of Arctic cyclone forecast track error to low level temperature in the region of an Arctic cold front and a coastal front at the analysis time. The OSEs for this case reveal that Arctic cyclone track error is more sensitive to denial of existing observations than amplitude error. While lower level (below 700 hPa) observations had greatest impact on the surface cyclone during the early stages, upper level (above 500 hPa) observations had the dominant impact during its later evolution. Denying temperature from just three well-placed sondes substantially increased track error by degrading analyses of the TPV amplitude and its interaction with the waveguide and developing Rossby wave packet. These results are encouraging for further Arctic cyclone forecast improvements through addition of even a small number of well-placed observations.

Numerical analysis of multi-scale pressure pulsation on the energy accumulation for submarine-based tracking and pointing systems

One of the main goals of submarine designers and researchers is to estimate the influence of submarine fluid dynamics for submarine-based optical tracking and pointing systems. In this study, firstly, based on the basic flow governing equation and hierarchical grids, the numerical simulation method of DNS (direct numerical simulation) is adopted to simulate the seawater flow around the submarine at 6° yaw angle and 107 Reynolds number. Secondly, the transformation equations from the earth coordinate system to the optical axis system have been deduced and the ultimate influence of pressure torques on the tracking system is studied. Transfer functions of the coarse channel direct current (DC) torque motor and fine channel fast steering mirror (FSM) also have been modeled and deduced. On this basis, the time domain step responses of both subsystems are analyzed by MATLAB Simulink. Finally, performance analyses have been deduced by comparing the error variation and vortices evolution. It revealed that the frequency characteristics of multi-scale pressure pulsation mainly depended on the lengths of submarine hull or its appendage, as well as the fluid dissipation and random interaction. In general, the coarse channel appears a good compensation performance at low frequency and large amplitude error that caused by the middle-scale pressure pulsation. Contrarily, the FSM fine channel exerts an excellent control effect for higher frequency and small amplitude error caused by small-scale pressure pulsations.

Amplitude error correction in matrix simulators of radar targets

Problem statement. The compensation problem of the amplitude error occurring when modeling radar targets using matrix simulators is considered. The relations that reveal the concept of this error are given. The example shows that the amplitude of the simulated echo signal differs from the amplitude of the real one.Objective. Justification of a method for correcting the amplitude error observed when simulating echo signals from radar targets using emitter matrices.Results. It is shown that when the scanning radiation pattern is oriented normal to the matrix base, the amplitude of the simulated echo signal does not depend on the angular target position. Based on this, a method was proposed to eliminate the error through pre-distortion of the echo signal amplitude. The ratio for calculating the predistortion multiplier coefficient is obtained. In the framework of a numerical experiment, the amplitude of the simulated echo signal was estimated for various angular positions of the scanning radiation pattern without taking into account predistortion and with predistortion. The experimental results confirmed the correction effectiveness.Practical implications. The results obtained allow increasing the adequacy of modeling radar objects by matrix simulators by ensuring that the amplitude of the simulated echo signal corresponds to the amplitude of the real one.

Recommendation in Measuring Digital Volume Pulse for Mobile Application (Preprint)

BACKGROUND As the demand to acquire bio-signals and use them for health management in daily life increases, it is becoming more common to mount photoplethysmography on mobile devices such as smartphones and smart watches. However, though it is very important to know the optimized signal measurement conditions due to resource limitations such as computing power and battery life in the mobile environment, the optimal signal acquisition conditions required to derive clinically meaningful results has not been proposed yet. OBJECTIVE This study aims to suggest appropriate criteria for measurement photoplethysmogram with clinical utility by identifying the changes in photoplethysmogram waveform with decreasing sampling frequency and quantization bit depth. METHODS Photoplethysmograms recorded at a 1-kHz sampling frequency and 16-bit quantization bit depth were converted to signals with sampling frequencies of 500-, 250-, 100-, 50-, 25-, and 10-Hz by means of down-sampling, and then we did re-quantization to convert the quantization bit depth into 16, 14, 12, 10, 8, and 6 bits for each down-sampled signal. Degradation of the signal was quantified in terms of morphological change using normalized root mean square error and feature-point deviation using mean absolute error at representative photoplethysmogram features such as pulse onset or systolic peak. RESULTS Although there were differences according to pulse onset and systolic peak, the sampling frequency of ≥ 250-Hz and 16-bit quantization bits are required in order to have ≤ 1 ms of timing error and a normalized amplitude error of ≤ 1%. In addition, a sampling frequency ≥ 100-Hz and a 12-bit quantization bits are recommended to have feature-point time errors and amplitude errors of < 10 ms and a normalized amplitude error of < 10%. CONCLUSIONS Our results highly recommend that 16-bit quantization bit depth and ≥ 250-Hz sampling to secure < 1% of error, and ≥ 25-Hz sampling and ≥ 10-bit quantization bit depth for minimal use compared with photoplethysmogram obtained by 1-kHz sampling and 16-bit quantization bit depth.