Questions tagged [radio-frequency]
The radio-frequency tag has no summary.
306 questions
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MRI 180° RF pulse and spin synchronization
(How) Is it possible for a 180° RF pulse to inverse the net magnetization $M$ and synchronize individual spins (if spins were synchronized wouldn't that imply that there is some non zero $M_{xy}$ ...
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Off resonant driving of a MW/RF cavity
Let's say I have a cavity resonant at 10 GHz with a Q factor of 1000. Given the Lorentzian shape of the cavity, I can also drive the cavity at, say 100 MHz. Of course the response will be very very ...
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Question about 100 MHz resonator
I would like to apply an electric field of 100 V/cm, along the $z$-axis (defined by an externally applied DC field), with a frequency of 100 MHz at the location of an atomic cloud (everything is ...
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Do window screens block WiFi? [closed]
I'm thinking of putting a wifi satellite on a screened in porch outside, to cover my yard. The Internet seems to think that wire screens don't block wifi, but wifi has a wavelength of 2 inches or more,...
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Wavelength or frequency border of radio waves and microwaves
I'm unable to find a precise definition of the wavelength or frequency delimiting the radio waves and the microwaves. Some sources are saying that the frequency $f = 1\mathrm{GHz} = 10^9 \, \mathrm{...
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How is $\rm GaN$ used in Active Electronically Scanned Array (AESA) radars?
Many Active Electronically Scanned Array (AESA) radars are based on Gallium Nitride ($\rm GaN$).
I understand in principle how AESA radars work. What role does the $\rm GaN$ play? Why not some other ...
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Why is the effect of an $\alpha_\phi$ radiofrequency pulse is given by $R_{z'}(\phi)R_{x'}(\alpha) R_{z'}(-\phi)$?
In 1, page 82, it is written that "the effect of an $\alpha_\phi$ pulse can be represented by three cascaded spin rotations. In terms of rotation matrices:
$
M(0^+) = R_{z'}(\phi)R_{x'}(\alpha) ...
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Why does the Spin Echo sequence refocus dephase due to magnetic field inhomogeneities and gradient echo does not?
My explanations come from Richard Buxton's book (Introduction to functional magnetic resonance imaging).
We know that Spin Echo sequence can be summerized as
90° pulse - wait TE/2 - 180° pulse - wait ...
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Is the magnetic field in an ideal coaxial cable carrying a TEM wave solely defined by the Ampere/Maxwell displacement current?
If I have a plain TEM wave in an ideal coaxial cable, a simple solution to the wave equation assumes a wave in the source free region between the center conductor and the shield. The magnetic field is ...
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RF Heating in a Dielectric
Trying to understand rf heating in dielectrics. Suppose I have a high frequency AC current around 50 - 100 MHz on a wire adjacent to a dielectric..
This creates an associated electric field $\mathbf{E}...
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Passing photoauostic audible messages via mid-infrared lasers can be done. Can we achieve this with a microwave?
In medicine, Photoauostic spectrography is used in non invansive glucose monitoring. To acheive this, we use invisible laser (Mid-Infrared) range in electromagnatic spectrum.
The photoacoustic effect ...
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Can refraction change a wave's frequency?
Can refraction change a wave's frequency under any circumstances ?
If yes, what conditions must apply for this to occur ?
Is this a common phenomenon or only happening in extreme circumstances (such ...
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Deeper explanation of why Spin-Echo's 180 degree refocusing pulse recovers static magnetic field inhomogeneities vs Gradien-Echo which does not
I have studied the Spin-Echo pulse sequence for some time now, and read many explanations in different books and courses.
I know that the 180 degrees RF pulse (applied half way between the 90 degrees ...
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Why does this RLC behavior differ from what equations predict?
In order to better understand RLC behavior under current sources, I constructed the simple circuit below and attempted to analyze it. However, my equations do not agree with simulation results.
The ...
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Phase-Based Ranging
I've been reading a lot about Phase-Based Ranging (PBR), and it's all starting to become very intuitive.
BUT; There is one technical, but extremely important, detail that seems to escape me. When the ...
