Questions tagged [microwaves]

Microwaves, broadly defined, are electromagnetic radiation with wavelengths ranging from one meter to one millimeter; or with frequencies between 300 MHz (100 cm) and 300 GHz (0.1 cm). This range includes both UHF and EHF (millimeter waves) and the entire SHF band (3 to 30 GHz, or 10 to 1 cm).

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Attenuation in microwave and optical communications

I have read that the attenuations of microwave transmission lines and optical fibers are ~1 db/m and ~ 0.2 db/km, respectively. I understand that these values depend on the geometry, design, and ...
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Concept of polarization in microwave rotational spectroscopy

I am trying to understand the concept of polarization of molecules after they are excited by a microwave pulse. The context is: The complexes are produced in a pulsed supersonic jet expansion of a ...
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Existing microwave trapped ion quantum computer?

In the recent paper Blueprint for a microwave trapped ion quantum computer, the authors envision a scalable design for a quantum computer, built from smaller ones implemented on silicon wafers, "using ...
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Why do rings form on microwaved CD/DVDs?

Here's a microwaved CD. As you can see, the disc has been destroyed, but there are very clear circular rings bridged with lines. Why are rings formed when microwaving discs?
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Are microwave-generating devices (gyrotrons) in the ITER system phased to heat plasma?

Provided electricity from grid is converted and supplies 24 gyrotrons, which generate electromagnetic waves, which in turn, will transfer their energy to the electrons of the ITER plasma to heat it up....
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Does a MASER beam stay un-dispersed like that of a laser?

We know that a laser beam has a very low dispersion rate. Does the same apply for a MASER (Microwave Amplification by Stimulated Emission of Radiation) beam?
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What is the lowest energy atomic transition ever detected and identified?

In this concise and insightful answer it was pointed out that atoms can have an extremely large (possibly infinite) number of bound excited states. The Rydberg formula represents a simple model for ...
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In theory, Is it possible irradiate a blob of matter -for instance- with microwaves in order to that matter emit more energy than has received?

Suppose that you want coerce a block of matter to lose his energy. I mean thermal energy. This should be done by irradiation of more energy. The final thermal energy should be lower that the original ...
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Can a microwave oven induce an accumulation of static charge in food?

I often "touch test" microwaved food to see if it is heated up enough to my preference. In doing so, I sometimes notice the characteristic tingle of a static discharge between the food and my finger (...
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How can I beforehand determine whether a material is a good candidate for a microwave sensor?

Is there a table of some sort or formula where I can determine before I test the material under a microwave sensor whether it will allow the microwaves to pass through and if so at what depth. for ...
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192 views

Does attenuation to RF waves increases with frequency?

I heard somewhere that RF waves at high frequency such as above 2GHz face more attenuation while passing through air, buildings and due to humidity as compared to 800Mhz and 2) Waves at 30-40GHz ...
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48 views

Subwavelength aperture vs microwave oven mesh

I am trying to understand why some subwavelength apertures radiate such as https://lo.epfl.ch/wp-content/uploads/2018/08/OE_14_10410_Oct2006.pdf and why others don't. For eg. the mesh inside a ...
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Why does Skywave only work for a small frequency band?

So it is often said that waves in the HF band (3-30MHz) use skywave propagation to beam signals around the curvature of the Earth. My question is why is there this narrow limit to what is able to ...
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165 views

Electromagnetic wave patterns in waveguides for different modes like TE10, TM11

I have read about different waveguide and their different modes like TE10, TE11, etc. In many books, the EM wave patterns are given, where they were said to be drawn from the waveguide's equations. ...
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43 views

What is the formula for the wavelength of radiation produced by non-relativistic electrons travelling through an undulator?

Is it simply equal to the length of the undulator periods? Or does it depend on the electrons' velocity and the strength of the magnetic field? Thanks.
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Why does wavelength decide the size/diameter of these holes in the microwave door?

I've read here that microwaves are blocked by the holes in a microwave window because the holes on the door are small enough to prevent the microwaves from passing through. However, if wavelength is ...
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32 views

Time Domain Reflectometer

How can I analyze the data time domain reflectometer measurement from this picture?
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3k views

Advantages/disadvantages of a cylindrical microwave oven cavity in comparison to a rectangular cavity

Why are rectangular cavities preferred for standard microwave ovens with a frequency of 2.45 Ghz? What is the reason that you can hardly find a circular cavity? What are the disadvantages of ...
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221 views

Electric fields with different frequencies, total intensity?

What happens when electric fields with different frequencies are combined? Is it possible to calculate the intensity of the total electric field? For a project, I need to simulate a brain treated ...
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139 views

Are microwaves sinusoidal or is that just a model?

I know that projectiles are parabolas because I can derive that from constant acceleration. And the height of a Ferris wheel rider vs. time is demonstrably a sine wave. What is the underlying thing ...
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Why does a cold glass container when heated in a microwave breaks down? But a container at a room temperature does not?

I have noticed that when I take some eatable kept in a glass container, out of the fridge, when they are already at a low temperature (around 3-4 degrees) and then try to heat it up in a microwave ...
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36 views

How to read a meter for radio and microwaves?

I am not clear on how to read this meter for radio waves and microwaves. The bottom band shows it measures from .01 to 1. First, I'm not sure what the units mean (mW/cm2). Radio waves are from 30KHz-...
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Faraday cage for 5G?

I'm interested in making a faraday cage that will block both standard and 5G wireless signals- essentially to make a tabletop box that people can put their phone in to be completely undisturbed, and ...
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35 views

Klystron output voltage, cavity physics

Can you please explain why almost nowhere do I see such a parameter as the output voltage from a klystron, it's easy to find the DC accelerating voltage of the beam and the electron bunch densities ...
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Why does a wave of single frequency travelling through the waveguide has group velocity?

Suppose we have a waveguide which is fed with electromagnetic wave having a single frequency of say 4GHz, if we are given the cutoff frequency we can determine the group velocity, but in order to ...
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Is there any factors depends for electromagnetic waves?

I am staying in hostel. One person said me that he is getting better connection with the wifi when the door is opened. I am wondering that what an electromagnetic wave can do with the door? Is there ...
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28 views

Leaked electric field in Transmission Line theory

In the previous image I can't understand why the leaked electric field in plate conductors is axial (On the same axis of propagation), And if it becomes axial then the wave in the conductor is not <...
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43 views

What's the difference between source current and conduction current?

Related Going through Pozar's Microwave Engineering, we have a derivation of Poynting's theorem which begins as follows. "If we have an electric source current $\bar{J_S}$ and a conduction current $\...
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What factors affect the amount of microwave absorption?

I am planning to do an investigation on factors affecting the amount of microwave absorption. I understand how microwave radiation heats objects, but do factors such as color affect the amount of ...
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Reflection Coefficient — propagation over a plane earth

In Section 2.1.2 "Propagation Over a Plane Earth" of [1], the author wrote: The reflection coefficient, $R$, of the ground depends on the angle of incidence, $\theta$, the polarization of the wave, ...
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Does the microwave generating component in a microwave operate under the same physics as an antenna radio transmitter?

Essentially does the component of a microwave which generates those microwave photons operate using an AC power supply connected to a broken circuit which causes an oscillating dipole to radiate ...
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44 views

Do conductors reflect Wifi signals? If so why?

I know electric field can't pass through conductors, but I have seen people surround their wifi router by soda can (not entirely) for better signal strength. I want to know what really happens there.
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How to devise a microwave power sensor?

I am fairly aware of the general thermistor/ diode/ thermocouple methods of sensing microwave power. Currently my requirements are simpler: A device that senses only microwave power incident on it - ...
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Mode expansion inside a waveguide

In the classic book by Collin (Foundations for Microwave Engineering, 2nd ed.), the author postulates on p. 278 that, given a waveguide structure that stretches along the $z$ axis with open ends (see ...
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Transmitted energy and transmitted wave phase in microwave structures

I have two questions about waves in large microwave structures. So the system I'm currently working on can be simulated as lossless transmission lines put together to one long structure. Without ...
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274 views

Waveguide horn antenna & inverse square law

With a lab waveguide / horn antenna setup similar to image (without bends), we made the following measurements. Now we thought this could be used to demonstrate the observation of the inverse square ...
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229 views

Hydrogen & Noble Gases in a Microwave

I was watching some Youtube videos of people microwaving helium and neon in a microwave. I could not find anything showing hydrogen in a microwave. However, as I was watching the videos I noticed ...
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What are the possible dangers of removing the microwave shielding?

Would removing the shielding from a domestic microwave door allow the microwaves to cause damage to a consumer grade video camera, and if so, what damage would it cause?
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Phase noise measurement with an IQ mixer

I have a question regarding a measurement scheme of phase noise that I'm trying to implement. The idea is that I have two identical signal generators (I actually do) that generate a sinusoidal voltage ...
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227 views

What are the properties of the electromagnetic radiation from a magnetron?

There are different modes of EM radiation. A bulb emits photons in a wide range of wavelengths and without polarisation. Radio waves are polarized modulated radiation. What is about the radiation ...
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647 views

Loaded Quality Factor

I came up with an expression for the reflected power of a resonator: $$\left| \Gamma \right|^2 = 1 - \frac{1-\left(\frac{\kappa - 1}{\kappa + 1}\right)^2}{1 + 4 \left( \frac{Q_U}{(\kappa + 1)} \frac{\...
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Dielectric heating - does EM field transfer energy to polar molecules?

In AC field, polar molecule are trying to align with external field. At high freguencies, changes of field are so quict, that molecules cannot align with it. This leads to increasing kinetic energy of ...