Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [near-field]

16 questions
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E field probe or H field probe to detect

I have a board that is failing radiated EMC tests. There are narrowband spikes with 50 MHz intervals (300 MHz, 350 MHz, 400 MHz, etc.) I believe it has something to do with a clock (I suspect so since 50 MHz seems to be the "base frequency" and that…
aaq
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Does this sensor measure electrical or magnetic fields (with oscilloscope)

I want to measure electrical and magnetic fields of the frequency 50Hz to 1MHz with my oscilloscope. For electrical fields I learned that any bunch of metal will work. For magnetic field derivation with respect to time I learned that a search coil…
Hansebenger
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NFC standards ISO 14443, ISO 15693 and ISO 18000-3. Which of them are most supported by smartphones?

I want to do this: mobile app <-> NFC <-> microcontroller, in order the MCU can communicate with Android or iOS apps via NFC hardware. I have two options of low-cost NFC chips, these chips don't support the same standards. Supported standards…
abomin3v3l
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Near-end scan different frequency magnetic field propagations in ideal DC source

I installed a simple PCB on Ansys siwave. I defined the power lines. And I defined an ideal voltage source that gives only 18 V on the pins. I set the near fields analysis as you can see. interestingly, in near field scanning, I see magnetic fields…
Electronx
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How should I use characteristic mode analysis for antennas that are needed for near field imaging?

I am designing an electrically small microstrip patch antenna, and its "radiative" near field (r = wavelength) reaches quite long enough for the whole imaging region. Basically, I don't need its power to be radiated to the far field. According to…
Lucifer Holmes
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Using a far field UHF RFID in the near field range

I have a 902 MHz to 928 MHz UHF 8dBi far-field RFID antenna connected to a reader. I want to read RFID tags. What will be the consequences if I used this UHF antenna in the near field range when it is meant to be used in the far-field range? This is…
JoeyB
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Prevent Reception from an Extended Distance (Beyond Design)

I have a magnetic field that is being induced onto a power line by a transmitter, which is following the length of the power line to the receiver. The receiver communicates via a loosely coupled coil with the transmitter. This artificially…
Electric Pet
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Designing 60hz antenna to detect electric field

I am working on designing an antenna to detect 60Hz electric field. I came across the microstrip antenna being used to detect the field. Before designing the antenna I wanted to maek sure this is the right way, So I took a piece of 2 layer PCB(both…
Karthik
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Why is the near-field radius of a small antenna lambda/2PI?

If I have a small antenna, the near-field is said to extend to \$\frac\lambda{2\pi}\$: The outer boundary of the reactive near-field region is commonly considered to be a distance of \${\textstyle {\frac {1}{2\pi }}}\$ times the wavelength (i.e.,…
Gruber
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Can PN7150 NFC controller deactivate RF Interface?

I have used the PN7150 NFC chip from NXP in autonomous polling mode with LPCD disabled. I can detect NFC Tag and can see NFC coil signals are changing as the NFC tag is detected. PN7150 VDDTx current consumption is 25mA when NFC Polling is…
Taher Kawantwala
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Near Field from a Dipole Antenna

What are the equations defining the near field of a half-wave dipole antenna? What is the rate of decay of E-field and H-field in the near field (both reactive and radiative zones)? How are the equations different from those for an Infinitesimal…
Yasir Ahmed
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Near-field microwave antenna design

How to I design an antenna which produces a strong field within the antenna, but doesn't radiate out or reflect back to the source? (as much as possible) I'd like ideally to have a planar structure (manufacturable with PCB traces), matched to 50…
Alex I
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How to get rid of 19kHz electrical fields

The mains of my German flat has 19kHz electrical fields on hot, neutral and! ground wire. I don't have to get rid of them entirely but I want to achieve 20dB reduction while sitting in front of my computer with grounded power supply. How to achieve…
Hansebenger
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Implement a data protocol between a smartphone and a MCU via NFC hardware?

If I'm able to develop a mobile app which is able to use the NFC hardware of a smartphone to write/read through it. And if I have a board containing a MCU and a NFC transponder like the IC from ST Microelectronics M24LR04E which can also make…
abomin3v3l
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Why do LF RFID tags use near field and why is reading distance longer with UHF RFID?

Why do LF/HF RFID tags use the near field (magnetic coupling) and not the far field? Well, I guess it's easier. The two antennas can just be modeled as a "transformer" and power transfer is straight forward. But would it be possible to use the far…
divB
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