scholarly journals SELECTIVE HIGH-SENSITIVITY RADIOMETER SWITCHING FREQUENCY AMPLIFIER WITH FREQUENCY RESPONSE TEMPERATURE COMPENSATION

2021 ◽  
pp. 88-95
Author(s):  
Oleksii Yanenko ◽  
Leonid Virchenko
Keyword(s):  
Frequency Response ◽  
High Sensitivity ◽  
Switching Frequency ◽  
Third Order ◽  
Transistor Channel ◽  
Modulation Radiometer ◽  
Low Intensity ◽  
Order Filter ◽  
Technical Requirements ◽  
Selective Amplifier

Problems. It is noted that the measurement of low-intensity microwave signals of various physical bodies and biological objects is associated with the need to provide high sensitivity, which can reach 10-14 -10-15 watts. The authors of the article studied the selective (selective) filter-amplifier of the switching frequency of the high-sensitivity modulation radiometer as one of the elements that have a significant impact on the sensitivity and accuracy of measurement, and developed recommendations for improving the stability of its parameters. The purpose of the research. The peculiarities of the modulation radiometer conversion channel operation are considered and the role of the selective switching frequency amplifier in providing such sensitivity is determined. The input and output signals of the selective amplifier, their relationship and the effect on the sensitivity of the radiometer were obtained and analyzed. The necessity of application of compensation of influence of temperature on characteristics of the filter taking into account temperature coefficients of elements of the scheme is proved. Conclusions. Modeling of a selective amplifier with a third-order filter was performed, the amplitude-frequency characteristic and the zone of its possible displacement at the maximum operating temperature were obtained. The structural and schematic diagram of the selective amplifier with automatic consideration of temperature influences, due to the introduction of feedback and correction of the frequency response of the filter has been developed. The main parameters of the bandpass filter built on the feedback circuit are determined. The use of a field-effect transistor channel connected in series with the resistors of the frequency-forming circuits of the third-order filter is proposed as an element of frequency response correction. The technical requirements for modeling and development of a selective amplifier are determined, which provide opportunities for implementation in practice. The research can be used to build a highly sensitive radiometric system for measuring low-intensity signals in areas such as biology and medicine.

Biological effects of low-intensity radiofrequency fields and risk assessment for biota

2020 ◽  
Vol 60 (9) ◽  
pp. 592-596
Author(s):  
Elena I. Sarapultseva ◽  
Darya V. Uskalova ◽  
Ksenya V. Ustenko
Keyword(s):  
Radio Frequency ◽  
Electromagnetic Radiation ◽  
Electromagnetic Fields ◽  
Negative Impact ◽  
Biological Effects ◽  
High Sensitivity ◽  
Communication Technologies ◽  
Natural Ecosystems ◽  
Low Intensity ◽  
Different Levels

Despite the fact that there are still conflicting opinions about the damage caused by modern wireless communication technologies, most scientists report on the negative biological effects of low-intensity radio frequency electromagnetic radiation at different levels of the organization of live nature. There is no doubt that there is a need not only for a sanitary and hygienic assessment of man-made electromagnetic effects on humans, but also for an environmental assessment for biota. The purpose of the study was to assess the potential environmental risk of electromagnetic impact in the centimeter range on natural ecosystems. The initial data were the authors' own results in the field of radiobiology of non-ionizing radiation, as well as published of other researchers. The article analyzes the biological effects of radio frequency electromagnetic fields detected in organisms of different systematic groups and levels of organization. The data on the non-thermal biological effects of electromagnetic fields indicate a high sensitivity of different species to this factor. The analyzed research results emphasize the need to take into account the features of non-thermal effects of electromagnetic radiation on biota, since these radiations can have a negative impact on different hierarchical levels in natural ecosystems.

scholarly journals Transparent and Flexible Vibration Sensor Based on a Wheel-Shaped Hybrid Thin Membrane

Micromachines ◽  
2021 ◽  
Vol 12 (10) ◽  
pp. 1246
Author(s):  
Siyoung Lee ◽  
Eun Kwang Lee ◽  
Eunho Lee ◽  
Geun Yeol Bae
Keyword(s):  
Frequency Response ◽  
High Sensitivity ◽  
Vibration Sensor ◽  
Human Machine Interaction ◽  
High Transparency ◽  
Vibration Sensors ◽  
Low Stiffness ◽  
Machine Interaction ◽  
The Internet Of Things ◽  
Ultrathin Membranes

With the advent of human–machine interaction and the Internet of Things, wearable and flexible vibration sensors have been developed to detect human voices and surrounding vibrations transmitted to humans. However, previous wearable vibration sensors have limitations in the sensing performance, such as frequency response, linearity of sensitivity, and esthetics. In this study, a transparent and flexible vibration sensor was developed by incorporating organic/inorganic hybrid materials into ultrathin membranes. The sensor exhibited a linear and high sensitivity (20 mV/g) and a flat frequency response (80–3000 Hz), which are attributed to the wheel-shaped capacitive diaphragm structure fabricated by exploiting the high processability and low stiffness of the organic material SU-8 and the high conductivity of the inorganic material ITO. The sensor also has sufficient esthetics as a wearable device because of the high transparency of SU-8 and ITO. In addition, the temperature of the post-annealing process after ITO sputtering was optimized for the high transparency and conductivity. The fabricated sensor showed significant potential for use in transparent healthcare devices to monitor the vibrations transmitted from hand-held vibration tools and in a skin-attachable vocal sensor.

Design of a Third-Order Filter with 10 GHz Center Frequency

2021 ◽  
pp. 225-233
Author(s):  
Hai Wang ◽  
Zhihong Wang ◽  
Guiling Sun ◽  
Rong Guo ◽  
Ming He ◽  
...  
Keyword(s):  
Center Frequency ◽  
Third Order ◽  
Order Filter

scholarly journals Design of an underwater acoustic array for full ocean depth multi-beam echo sounder

2019 ◽  
Vol 283 ◽  
pp. 05002
Author(s):  
Haoqi Hao ◽  
Tiejian Xia ◽  
Min Xie
Keyword(s):  
High Reliability ◽  
Integrated Design ◽  
High Sensitivity ◽  
Underwater Acoustic ◽  
Technical Requirements ◽  
Planar Array ◽  
In Series ◽  
Stable Performance ◽  
Acoustic Array ◽  
Echo Sounder

In order to meet the technical requirements of full ocean depth multibeam echo sounder, the underwater acoustic array must have the ability of wide coverage, broadband response, high sensitivity and high reliability. This paper presents a design of underwater acoustic array based on Mills cross configuration with separate transmitting and receiving units. The arrays have modules design, hence the beamwidth of the array can be adjusted according to particular installation requirements. The working frequency band of the arrays is between 10.5kHz to 13.5kHz, and the coverage angle can cover -71.6°~71.6°. The Integrated design is used to achieve a wide-angle beam coverage of the planar array, which combines the transducer and the sound baffle together to realize a wide directivity of the array elements. The longitudinal bending transducers are designed to meet the broadband requirements for the transmitting array, which are Tonpilz transducers with flexural radiating head. On the other hand, each element of the receiving array is composed of several hydrophones, which are connected in series to achieve high sensitivity. The double-layer watertight technology is also applied in our design, ensuring stable performance and long service life.

scholarly journals Optimization of Transformer Winding Deformation Assessment Criterion Considering Insulation Aging and Moisture Content

Energies ◽  
2020 ◽  
Vol 13 (24) ◽  
pp. 6491
Author(s):  
Qian Wu ◽  
Yizhuo Hu ◽  
Ming Dong ◽  
Bo Song ◽  
Changjie Xia ◽  
...  
Keyword(s):  
Moisture Content ◽  
Frequency Response ◽  
High Sensitivity ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Response Curves ◽  
Insulation Aging ◽  
Transformer Winding ◽  
Winding Deformation ◽  
Paper Insulation

Frequency response analysis is widely used to diagnose transformer winding deformation faults due to its high sensitivity, strong anti-interference capability, and equipment portability, but the results of frequency response analysis can be affected by insulation aging and moisture in the transformer, leading to errors in the diagnosis of winding deformation faults. Currently, there is no effective method to prevent such errors. This paper focuses on optimizing the criterion for diagnosing winding deformations when insulation aging and moisture are present. First, the winding frequency response curves of oil-paper insulation were determined by combining insulation aging and moisture tests of the oil-paper insulation with frequency response simulations of the transformer winding. Next, the winding deformation criterion predicting the likelihood and extent of errors diagnosing transformer winding deformations due to the insulation aging and moisture content is discussed. Finally, the corresponding criterion optimization method is proposed. The corresponding results show that insulation aging and moisture can lead to errors when using the correlation coefficient R criterion to diagnose the transformer winding deformations. Moreover, the possibility of winding deformation errors caused by the change of insulation state can be reduced by introducing the corresponding auxiliary criterion through comparing the capacitance change rate based on the frequency response method and that based on the dielectric spectrum method.

scholarly journals Frequency Response Stabilization and Comparative Studies of MET Hydrophone at Marine Seismic Exploration Systems

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1944 ◽  
Author(s):  
Egor Egorov ◽  
Anna Shabalina ◽  
Dmitry Zaitsev ◽  
Sergey Kurkov ◽  
Nikolay Gueorguiev
Keyword(s):  
Frequency Response ◽  
Field Tests ◽  
High Sensitivity ◽  
Seismic Exploration ◽  
Joint Stock Company ◽  
Experimental Sample ◽  
Frequency Range ◽  
Stock Company ◽  
Low Frequencies ◽  
Marine Seismic

Low frequency hydrophone with a frequency range of 1−300 Hz for marine seismic exploration systems has been developed. The operation principle of the hydrophone bases on the molecular electronic transfer that allows high sensitivity and low level self-noise at low frequencies (<10 Hz) to be achieved. The paper presents a stabilization method of the frequency response within the frequency range at a depth up to 30 m. Laboratory and marine tests confirmed the stated characteristics as well as the possibility of using this sensor in bottom marine seismic systems. An experimental sample of the hydrophone successfully passed a comparative marine test at Gelendzhik Bay (Black Sea) with the technical support of Joint-Stock Company (JSC) “Yuzhmorgeologiya”. One of the main results is the possibility of obtaining high-quality information in the field of low frequencies, which was demonstrated in the course of field tests.

Analytical Methodology to Design Third-Order Filter (LCL) for Battery Chargers

2020 ◽  
Author(s):  
Carla Aparecida Felipe ◽  
Edivan Laercio Carvalho ◽  
Emerson Giovani Carati ◽  
Leandro Michels ◽  
Lucas V. Bellinaso ◽  
...  
Keyword(s):  
Third Order ◽  
Analytical Methodology ◽  
Order Filter ◽  
Battery Chargers

Detection of Damage Extension in Cantilever Beams Using Change Ratio of Frequency Response Functions

2011 ◽  
Vol 50-51 ◽  
pp. 875-879
Author(s):  
Hai Lei Jia ◽  
Yin Zhao
Keyword(s):  
Frequency Response ◽  
Natural Frequencies ◽  
Dynamic Properties ◽  
Damage Index ◽  
High Sensitivity ◽  
Cantilever Beams ◽  
Response Functions ◽  
Full Spectrum ◽  
Structural Dynamic ◽  
Low Dimensional

Frequency response function (FRF) is a fundamental dynamic index, which is capable of reflecting structural dynamic properties using full-spectrum information. In spite of distinct merits over conventional modal parameters, the FRF has an observable drawback of multi-dimensionality, unsuited for damage characterization. Such a situation motivates an interesting subject, i.e., extracting low-dimensional, high-sensitivity damage index from the FRF. This study focuses on developing a valid damage index, called FRF change ratio, to detect extension of damage. An experiment towards cantilever beams is systemically conducted. The results show that the FRF change ratio can effectively reflects damage extension, and it is more sensitive than conventional natural frequencies. This new damage index holds promise for practical damage detection in beam-like structures.

scholarly journals Altered ventricular mechanics after 60 min of high-intensity endurance exercise: insights from exercise speckle-tracking echocardiography

2015 ◽  
Vol 308 (8) ◽  
pp. H875-H883 ◽  
Author(s):  
Glenn M. Stewart ◽  
Akira Yamada ◽  
Luke J. Haseler ◽  
Justin J. Kavanagh ◽  
Gus Koerbin ◽  
...  
Keyword(s):  
Mean Arterial Pressure ◽  
Cardiac Troponin ◽  
Troponin T ◽  
High Sensitivity ◽  
Left Ventricular ◽  
Cardiac Troponin T ◽  
Low Intensity ◽  
Exercise Challenge ◽  
Exercise Induced ◽  
Low Intensity Exercise

Transient reductions in myocardial strain coupled with cardiac-specific biomarker release have been reported after prolonged exercise (>180 min). However, it is unknown if 1) shorter-duration exercise (60 min) can perturb cardiac function or 2) if exercise-induced reductions in strain are masked by hemodynamic changes that are associated with passive recovery from exercise. Left ventricular (LV) and right ventricular global longitudinal strain (GLS), LV torsion, and high-sensitivity cardiac troponin T were measured in 15 competitive cyclists (age: 28 ± 3 yr, peak O2 uptake: 4.8 ± 0.6 l/min) before and after a 60-min high-intensity cycling race intervention (CRIT60). At both time points (pre- and post-CRIT60), strain and torsion were assessed at rest and during a standardized low-intensity exercise challenge (power output: 96 ± 8 W) in a semirecumbent position using echocardiography. During rest, hemodynamic conditions were different from pre- to post-CRIT60 (mean arterial pressure: 96 ± 1 vs. 86 ± 2 mmHg, P < 0.001), and there were no changes in strain or torsion. In contrast, during the standardized low-intensity exercise challenge, hemodynamic conditions were unchanged from pre- to post-CRIT60 (mean arterial pressure: 98 ± 1 vs. 97 ± 1 mmHg, not significant), but strain decreased (left ventricular GLS: −20.3 ± 0.5% vs. −18.5 ± 0.4%, P < 0.01; right ventricular GLS: −26.4 ± 1.6% vs. −22.4 ± 1.5%, P < 0.05), whereas LV torsion remained unchanged. Serum high-sensitivity cardiac troponin T increased by 345% after the CRIT60 (6.0 ± 0.6 vs. 20.7 ± 6.9 ng/l, P < 0.05). This study demonstrates that exercise-induced functional and biochemical cardiac perturbations are not confined to ultraendurance sporting events and transpire during exercise that is typical of day-to-day training undertaken by endurance athletes. The clinical significance of cumulative exposure to endurance exercise warrants further study.

Design and Analysis of Thermal-Bubble-Based Micromachined Accelerometer

Volume 3 ◽  
2004 ◽  
Author(s):  
Ke-Min Liao ◽  
Rongshun Chen ◽  
Bruce C. S. Chou
Keyword(s):  
Heat Transfer ◽  
Fluid Flow ◽  
Velocity Field ◽  
Numerical Simulations ◽  
Frequency Response ◽  
Proof Mass ◽  
Flow Behavior ◽  
High Sensitivity ◽  
The Other ◽  
High Flux

In this study, a novel thermal-bubble-based micromachined accelerometer with advantages of no proof mass, preferable frequency response, and high sensitivity is presented. Unlike the other techniques, the only moving element in the proposed device is a small thermal-bubble created by using a high flux heater to vaporize the liquid contained in the micro chamber. In order to improve the performance of the accelerometer, the basic physical characteristics of this sensor have been analyzed. Numerical simulations are conducted to study the heat transfer and fluid flow behavior of the device and to demonstrate the feasibility of our design. The temperature profile and the velocity field distribution under different applied acceleration have been acquired. Moreover, a method for manufacturing the accelerometer by using the techniques of micromachining is provided and the performance of the presented design has been examined. The results concluded that the proposed design has better response and sensitivity comparing to its counterparts.

Sign in / Sign up

Export Citation Format

Share Document