scholarly journals Measurement of induced currents in radio frequency magnetic fields based on near field antenna perturbations

AIP Advances ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 065202
Author(s):  
J. M. Jennings ◽  
A. Kar ◽  
R. Vaidyanathan
Keyword(s):  
Magnetic Fields ◽  
Radio Frequency ◽  
Near Field ◽  
Induced Currents

scholarly journals Impacts of Wireless Power on Medical Device Design Safety

2009 ◽  
Vol 3 (2) ◽  
Author(s):  
J. Schneider ◽  
L. Lucke ◽  
D. Wessels ◽  
T. Schauer
Keyword(s):  
Magnetic Fields ◽  
Power Systems ◽  
Radio Frequency ◽  
Medical Device ◽  
Medical Devices ◽  
Human Exposure ◽  
Near Field ◽  
Wireless Power ◽  
Evanescent Coupling ◽  
Time Average

Wireless power holds great promise for solving many power distribution problems. Medical device designers will need to understand the impact of the electromagnetic coupling used for wireless power systems to design safe electromagnetic environments and safe medical devices. One question for designers will be whether or not current standards and requirements used for testing the electromagnetic compatibility (EMC) of medical devices and human exposure go far enough to insure safe environments and safe and reliable medical devices in the presence of wireless power. Electromagnetic energy can be transferred in three ways: through induction, radio frequency waves, or resonant evanescent coupling. Nonradiative inductive coupling uses the magnetic fields created when current is passed through one coil to create a current in a second coil that is located very near the first coil. These systems usually operate in the 50 KHz to 10 MHz range. Radio frequency energy can be transferred through radiating electromagnetic waves over great distances at frequencies from the upper KHz to many GHz. Most recently, work has been done on resonant evanescent coupling which transfers power between resonant objects over a distance of a couple of meters at frequencies from 1–10 MHz. Safety and reliability of medical devices is confirmed by testing EMC emissions and susceptibility to IEC60601-1-2 and supporting standards. For example, one of the supporting standards, CISPR 11 calls for measuring the electric field of radiated emissions over 30 MHz and the magnetic field below 30 MHz at distances of 3–10 meters. Many of the effects of wireless power systems are in the near field and are not covered in the current test standards. The AAMI PC69 series of standards have some near field requirements but these standards tend to be industry specific – such as drug pumps or pacemakers. EMC immunity standards used to test EMC susceptibility barely mention magnetic immunity. The only test for magnetic fields recommends testing fields at the power frequencies of 50 and 60 Hz. There are few standards detailing safe limits for human exposure to the near field effects of wireless power as well. Historically human exposure standards have been based on time average thermal effects on tissue and not medical devices. IEEE's C95.1b has requirements for specific absorption rate limits averaged over a 6 minute period. A pulsed wireless power system could meet these requirements and be safe for exposed tissue, but if a patient has an implanted device, or is wearing an external medical device, the pulsed EM energy could affect it during the pulse. The German BGV B11 standard lists human exposure limits for electric and magnetic fields based on a time average and limits exposure based on which portion of the body is exposed. However, it is meant as a workplace standard not a medical device standard. Currently the FDA does not require meeting either of these standards. It is necessary to determine the appropriate limits and tests to ensure that medical devices safely use wireless power and continue to operate safely in the presence of wireless power.

Interactions of magnetic resonance imaging radio frequency magnetic fields with elongated medical implants

2000 ◽  
Vol 87 (9) ◽  
pp. 6188-6190 ◽  
Author(s):  
Chris D. Smith ◽  
Alexander V. Kildishev ◽  
John A. Nyenhuis ◽  
Kirk S. Foster ◽  
Joe D. Bourland
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Magnetic Fields ◽  
Radio Frequency ◽  
Medical Implants ◽  
Resonance Imaging

scholarly journals Uses of radio emission spectroscopy for non-contact and in situ diagnostics of low pressure radio frequency plasma processing

2021 ◽  
Author(s):  
Rajani K. Vijayaraghavan ◽  
Sean Kelly ◽  
David Coates ◽  
Cezar Gaman ◽  
Niall MacGearailt ◽  
...  
Keyword(s):  
Radio Emission ◽  
Radio Frequency ◽  
Emission Spectroscopy ◽  
Near Field ◽  
Plasma Processing ◽  
Diagnostic Technique ◽  
Primary Source ◽  
Low Pressure ◽  
Chamber Pressure ◽  
Rf Plasma

Abstract We demonstrate that a passive non-contact diagnostic technique, radio emission spectroscopy (RES), provides a sensitive monitor of currents in a low pressure radio frequency (RF) plasma. A near field magnetic loop antenna was used to capture RF emissions from the plasma without perturbing it. The analysis was implemented for a capacitively coupled RF plasma with an RF supply at a frequency of 13.56 MHz. Real-time measurements are captured in scenarios relevant to contemporary challenges faced during semiconductor fabrication (e.g. window coating and wall disturbance). Exploration of the technique for key equipment parameters including applied RF power, chamber pressure, RF bias frequencies and chamber wall cleanliness shows sensitive and repeatable function. In particular, the induced RES signal was found to vary sensitively to pressure changes and we were able to detect pressure and power variations as low as ~2.5 %/mtorr and ~3.5 %/watt, respectively, during the plasma processing during a trial generic plasma process. Finally, we explored the ability of RES to monitor the operation of a multiple frequency low-pressure RF plasma system (f1 = 2 MHz, f2 = 162 MHz) and intermixing products which suggests strongly that the plasma sheaths are the primary source of this non-linear diode mixing effect.

scholarly journals Design and Development Of Lecturer Attendance System Using Radio Frequency Identification (RFID)

2021 ◽  
Vol 10 (1) ◽  
pp. 15-27
Author(s):  
I Gede Sujana Eka Putra ◽  
Anthony Lee ◽  
I Made Tirta Mahayana ◽  
I Gede Agung Wicaksono Dharmayasa
Keyword(s):  
Radio Frequency ◽  
Radio Frequency Identification ◽  
Web Application ◽  
Academic Staff ◽  
Near Field ◽  
Literature Study ◽  
Master Data ◽  
Presence Data ◽  
Frequency Identification ◽  
The University

Lecturer attendance record is required by the university to know the presence of lecturers in teaching in class. In general condition, lecturer attendance is recorded on the attendance sheet, or input to web application accessed on a class computer. However, there are some problems in its implementation so that at the end, lecturer presence is carried out using a manual form where the academic staff needs to re-enter the lecturer attendance data into the applications. Based on the above, the authors designed and developed a lecturer attendance information system to record lecturers' attendance using radio frequency identification technology by implementing a near field communication card (NFC Card). The device used to record and read presence data during lectures, by tapping an Mi-fare NFC card to an NFC reader / writer device. The flow of this research method begins with a literature study of NFC card, observe the flow of lecture attendance process and data recorded into lecturer attendance sheet, analyzing the database design, the system design which has compatible with NFC reader and writer devices, designed system interface and continue to develop system. The result is system consists of master data, system attendance, verification and reporting module. The results show that NFC card implementation is more practical for lecturers in conducting lecture attendance and NFC card could be tapped out into an NFC device at a maximum distance up to 7 cm with the reading angle relative to NFC reader/writer with range 00 until 300 can read NFC Card.

Effects of radio frequency magnetic fields on iron release from cage proteins

2009 ◽  
Vol 30 (5) ◽  
pp. 336-342 ◽  
Author(s):  
Oscar Céspedes ◽  
Shoogo Ueno
Keyword(s):  
Magnetic Fields ◽  
Radio Frequency ◽  
Iron Release

scholarly journals High precision epidermal radio frequency antenna via nanofiber network for wireless stretchable multifunction electronics

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Yufei Zhang ◽  
Zhihao Huo ◽  
Xiandi Wang ◽  
Xun Han ◽  
Wenqiang Wu ◽  
...  
Keyword(s):  
Radio Frequency ◽  
Near Field ◽  
Transmission Efficiency ◽  
Stretchable Electronics ◽  
Information Communication ◽  
Long Distance ◽  
Human Machine Interaction ◽  
Natural Systems ◽  
Content Recognition ◽  
Healthcare Monitoring

Abstract Recently, stretchable electronics combined with wireless technology have been crucial for realizing efficient human-machine interaction. Here, we demonstrate highly stretchable transparent wireless electronics composed of Ag nanofibers coils and functional electronic components for power transfer and information communication. Inspired by natural systems, various patterned Ag nanofibers electrodes with a net structure are fabricated via using lithography and wet etching. The device design is optimized by analyzing the quality factor and radio frequency properties of the coil, considering the effects of strain. Particularly, the wireless transmission efficiency of a five-turn coil drops by approximately only 50% at 10 MHz with the strain of 100%. Moreover, various complex functional wireless electronics are developed using near-field communication and frequency modulation technology for applications in content recognition and long-distance transmission (>1 m), respectively. In summary, the proposed device has considerable potential for applications in artificial electronic skins, human healthcare monitoring and soft robotics.

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