Microwave Definition and 349 Threads

Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency ranges as microwaves; the above broad definition includes both UHF and EHF (millimeter wave) bands. A more common definition in radio-frequency engineering is the range between 1 and 100 GHz (wavelengths between 0.3 m and 3 mm). In all cases, microwaves include the entire SHF band (3 to 30 GHz, or 10 to 1 cm) at minimum. Frequencies in the microwave range are often referred to by their IEEE radar band designations: S, C, X, Ku, K, or Ka band, or by similar NATO or EU designations.
The prefix micro- in microwave is not meant to suggest a wavelength in the micrometer range. Rather, it indicates that microwaves are "small" (having shorter wavelengths), compared to the radio waves used prior to microwave technology. The boundaries between far infrared, terahertz radiation, microwaves, and ultra-high-frequency radio waves are fairly arbitrary and are used variously between different fields of study.
Microwaves travel by line-of-sight; unlike lower frequency radio waves they do not diffract around hills, follow the earth's surface as ground waves, or reflect from the ionosphere, so terrestrial microwave communication links are limited by the visual horizon to about 40 miles (64 km). At the high end of the band, they are absorbed by gases in the atmosphere, limiting practical communication distances to around a kilometer. Microwaves are widely used in modern technology, for example in point-to-point communication links, wireless networks, microwave radio relay networks, radar, satellite and spacecraft communication, medical diathermy and cancer treatment, remote sensing, radio astronomy, particle accelerators, spectroscopy, industrial heating, collision avoidance systems, garage door openers and keyless entry systems, and for cooking food in microwave ovens.

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  1. J

    How to calculate color temperature?

    I am looking for calculating color temperature in the IR/Microwave scale frequencies, for room temperature, 273K, 263K, 253K, all google is showing is about visible light and about display systems.
  2. J

    Materials that allow IR or UV light to pass through?

    Glass allows visible light to pass through I would like to find a list of materials that allows lights of different EM spectrum to pass through, not just the above, Searched throughout google, couldn't find any!.
  3. T

    Electronics 3D Printed 2.25 Ghz Microwave RADAR horn antenna

    So I printed this antenna with some conductive filament , however the microwaves seems to be going between the layers of the plastic. I surrounded it with Aluminum and still leaking, what can I do to fix it? Can conductive silver paint work?
  4. E

    RF and MW receivers' sensitivity

    I'm currently working on a novel RF and MW sensor and I wanted to know whether there is a paper that shows the current very best receiver sensitivity for a range of wavelengths in the RF-MW range in dBm preferably so I can directly compare to my device.
  5. T

    How many energy requires to increase 1℃ of 1 liter of water using MICROWAVE?

    we planning to heat water directly using microwave for industrial purpose. we need only 33deg Celsius for that I need this.
  6. R

    How ants can survive in a microwave

    Hello, This is a question that is haunting me when I saw small red ants go in and come out alive of microwave oven that was. Long story short, I was warming some food item in the microwave oven. When I put the container in the microwave oven, I missed to notice that there were few live...
  7. G

    Microwave oven transformer - safe use and setup questions

    Before we start, this transformer will be used in a closed shop, on a clear bench and via a remote switch. I will be in full view of the setup. I hope to try some Lichtenberg patterns. I see that the secondary, c. 2000V winding is referenced to the transformer core. What is the purpose of...
  8. T

    Microwave Oven: Why Are Grid Holes So Small?

    Since the wavelength microwaves used in microwave ovens have a wavelength of 12cm, why are the holes in the grid behind the glass so small? If they were 12cm would the microwaves still stay confined? If the small holes are only to "play it safe" that seems irrelevant since microwave has a...
  9. I like Serena

    How can we melt ice in a microwave efficiently?

    I've noticed that when I put a prefab meal in the microwave, the parts that are frozen over just don't defrost any time soon, even though the rest of the meal gets really hot. The reason is that the ice structure doesn't allow the polar water molecules to vibrate. My question: what can we do so...
  10. Cocoleia

    How does reflection affect the intensity of the microwave?

    Homework Statement I am working on a lab report, and I am a bit stumped at these questions: How does reflection affect the intensity of the microwave? Is all the energy of the wave striking the Reflector reflected? Does the intensity of the reflected signal vary with the angle of incidence...
  11. S

    I Where Does the Cosmic Microwave Background Come From and How is it Measured?

    Hello! I am reading some basic stuff in cosmology and I am a bit confused by the microwave background. As far as I understand, it is the radiation produced at the beginning of the universe, when the matter density was not that high so the photon can escape and travel freely. So the microwave...
  12. U

    Microwave Based Photonic Filters

    Hi ! I am actually seeking help regarding working principle of microwave based photonic filters from basics, I have tried a lot I did find allot of material but non of them were describing the basic working principle. Helping in this regard will be highly appreciable. Regards
  13. R

    Modern usage of non-navigational radio beacons

    How useful are non-navigational radio beacons (i.e., for determining current propagation conditions and testing) nowadays, whether microwave X band, HF, ELF, sub-mm wave, etc., considering the advent of computerized propagation modeling? Is the scarcity of non-amateur radio beacons a result of...
  14. T

    I Why hasn't the light from the CMB already passed us?

    If the cosmic microwave background occurred at the moment that electrons and protons joined together and photons were now free to travel across the universe, then why haven't those photons already passed it. I'm having a hard time understanding why we can see the CMB forever if it was simply a...
  15. E

    High end Radar receiver sensitivities

    I am looking for what the high end radar receivers can achieve in terms of sensitivity? I have had trouble finding examples online, I have seen -100 to -103dBm as typical sensitivities, but I'm looking for the cutting edge stuff. I've also seen the GPS satellites also have a sensitivity of...
  16. camerart

    What materials are safe in a microwave?

    Hi, I am carrying out some tests using the laser image transfer method, where the image of a circuit is put on a PCB as an acid resist, so leaving the circuit in copper. My thread PCB by Laser transfer. My method is a 'sandwich' of two stiff plates app 110x160mm bolted at the edges...
  17. C.Braestrup

    Microwave transparent material for ESR/EPR spectrometer

    Hi! Completely forgot about this great forum! I'm designing an electron spin resonance /electron paramagnetic resonance spectrometer, as an easier vacation from my diy NMR - while still utilizing much of the same setup. Issue is; I have an X-band (~12GHz) waveguide cavity in a magnet, and I...
  18. maearnie

    What Equipment is Needed in a Microwave Transmitter Control Room?

    Can someone enumerate the equipment needed in a microwave transmitter control room? i already searched the net and i somehow don’t understand anything haha. also can you please explain what each equipment does? thank you :)
  19. Spinnor

    B Energy in microwave cavity quantized?

    Consider the microwave cavity used in a particle accelerator to accelerate particle bunches. Before a bunch of particles enters the microwave cavity can we, if only in principle, quantum mechanically describe the state of the microwave cavity as a proper sum of microwave photon number states...
  20. C

    Open Circuit Termination for Waveguides in High Frequency Labs

    Hi everyone, I am trying to understand that why do we use open circuit terminator for wave guides or any RF element such as coupler and etc. I know if we just leave it open, it does not work as open circuit. But why?
  21. S

    Lower microwave absorption efficiency to increase penetration (cooking)

    A problem I encounter when microwaving food is that the centre is no penetrated by the microwaves so remains cool and I have to wait for the heat to be conducted through which takes a long time and undermines one of the advantages of microwaving which is the speed of the process. Would it make...
  22. R

    Are microwave susceptors attenuated in viscoelastic mediums?

    Are microwave susceptors attenuated in viscoelastic mediums ? I am experimenting with some widely known microwave susceptors like iron oxide and silicon carbide (materials that normally convert RF to heat quite effectively). In ceramic formulations they perform great, as expected. When...
  23. R

    Microwave susceptors are suppressed in viscoelastic mediums

    I am experimenting with some widely known microwave susceptors like iron oxide and silicon carbide (materials that normally convert RF to heat quite effectively). In ceramic formulations they perform great, as expected. When formulated in silicone rubber, they do not perform when subjected to...
  24. qnach

    Dielectric Antennae: Energy Feed-In/Take-Out Explained

    There are many webpage about dielectric antenna For instance, https://en.wikipedia.org/wiki/Dielectric_resonator_antenna But I cannot figure out where does the energy feed-in or take-out from the antenna?
  25. P G Krish

    Microwave oven is prevents mobile signal?

    Hi guys, If i put mobile phone into micro oven, Is this prevent mobile signal
  26. T

    B Spotting a Black Hole in the Microwave Background

    If we were to take a microwave picture of a region of space said to have a black hole, would we be able to spot the black hole? Would we see a cold spot surrounded by a more hotter background?
  27. patrykh18

    Calculate the frequency of microwave

    Homework Statement Two single frequency coherent microwave beams are directed from the same point towards a concave mirror. One beam is incident parallel to the principal axis of the mirror, 0.06m from the axis. The other beam passes through the focal point before striking the mirror. The...
  28. S

    How to focus and direct microwaves?

    I am interested in building a microwave powered toy helicopter purely for the fun of it. As we have discovered in our initial research, it isn't possible to direct the microwaves from a microwave oven magnetron too far. I know that those microwaves are of a similar wavelength (or is it?) What...
  29. P

    Drop in power in a directed microwave beam?

    Would it be a drop in power as the square of the distance in a directed microwave beam? Thanks!
  30. P

    Penetration depth of a microwave

    Hi, according to http://www1.lsbu.ac.uk/water/microwave_water.html and other sources the penetration depth of a microwave wave is proportional to the square root of the dielectric constant divided by the dielectric loss. For me it makes sense that as the dielectric loss increases more energy is...
  31. T

    A Is there a polarisation of the microwave background

    and if so what is it's orientation
  32. Geek007

    Infrared rays can't be used outside for communicaiton

    Hi there, We can't use Infrared rays outside for data communication of our home as sun light also contain infrared rays which possible will interfere with it.That's what i read in Data communication book. My Question is , Does sun rays also contain radio wave, microwave ? if yes, then why can't...
  33. Geek007

    Does Microwave support only Line of sight communication LOS?

    Hi there, Wifi uses either 2.5 GHZ band or 5 Ghz band and these bands lie in Microwave in EM spectrum. As i read in books, Microwaves are propagated using line of sight (LOS) technique, so sending and receiving antennas should need to be aligned accordingly. But WiFi signals are broadcasted...
  34. Tazerfish

    Why can't I kill the ice cubes >:o (in a Microwave Oven)

    I recently talked to a friend of mine about microwaves. Specifically that (to my knowlege) the microwave radiation is primarily absorbed by a rotational degree of freedom of water molecules. Which got me thinking. 1.First of all what would happen if you put a extremely cold ice cube ( with no...
  35. S

    B Understanding the Cosmic Microwave Background

    When a "layman" hears of the cosmic microwave background, and this layman also has a passing knowledge of big bang theory, it can be difficult for said layman to wrap his head around what the CMB really is. That layman might ask, wouldn't this primordial radiation have "passed" us by now, and...
  36. jfizzix

    Can fast objects get cooked by Cosmic Microwave background?

    Awhile ago, I was considering what sort of dangers a spacecraft moving at relativistic speeds would face in interstellar space. Aside from the obvious pieces of space dust being relativistic bullets in the ship's frame of reference, the cosmic microwave background (CMB) would become a big...
  37. J

    Difference between electric and microwave circuit?

    I understand in an electric circuit electrons in metallic materials move around by being directed by potential differences (fields!) I guess in a microwave circuit photons propagate as waves and are directed around and manipulated throughout the circuit by its geometry? Or have I got this...
  38. resurgance2001

    I Cosmic Microwave Background Radiation Anisotropies

    Hi This question may have already been answered elsewhere. If so please accept my apologies in advance. I am confused! The textbok(s) I am reading describe a whole bunch of different causes for there being temperature fluctuations in the CBM, so I am confused about which one(s) of these...
  39. P

    Microwave on capacitors battery power

    I live in an rv. My power comes from solar and ocassional boost from my generator. I have 3600wh in battery power. But i know its really bad for my batteries to draw lot of power fast. So i would like to create a capacitor bank that would stay charged. Ive done some calculations but not...
  40. C

    Energy from cosmic microwave background

    Hello everyone I've a question about the cosmic microwave background which my nephew asked me a couple of days ago. How much energy hits the Earth each year from the CMB? I'm assuming here that it is measurable in this way, but apologies if not. Thanks in advance for your help. Chris
  41. Anand Sivaram

    Microwave Heating -- 2.4GHz in, IR radiation out....

    Microwave oven operates at 2.4 GHz. Consider the situation of making tea or coffee in Microwave where water is heated to 100C to boil. Looking at Planck's law / Wien's law, 100C (373K) corresponds to a peak wavelength of 7.8nm or 38.6THz which is in Mid Infrared. Effectively materials...
  42. B

    Transmission line and infinite reflection coefficient

    Hello, I am taking some microwave engineering courses and was trying to explain the concept of reflection coefficients to my friend, but he asked me a question I am unable to answer... So we know that given a transmission line with characteristic impedance Z_0 terminated with a load impedance...
  43. J

    Does Microwave Mesh Effectively Block Radiation Due to Wavelength or Amplitude?

    Hi pf, Please could someone provide an explanation of why the relationship between the wavelength and size of the gap is the significant factor for determining whether or not it blocks radiation in particular reference to the mesh on the door of a microwave oven. It seems very simple when a...
  44. T

    Physics of a microwave - why does the turntable spin?

    Homework Statement A microwave oven operates by injecting electromagnetic waves with a frequency of 2.45 GHz into the cavity formed by the conducting metal shields on each face of the oven box. Explain, with the aid of sketches and simple calculations, why it is generally necessary to rotate...
  45. V

    Microwave tube mechanism of heating

    Hello, first of all, I understand, how microwave tube works but I'm interesting in how exactly the microwave heat up a things? What's the matter inside. I have heard about increasing energy of molecules of water by polarization them by micro-wave. But I have got a plate which is not from...
  46. S

    AC Mains frequency and microwave oven

    Does the frequency of the main affect the performance of a microwave oven? Having moved from Europe 50 Hz to the Philippines 60 Hz I can not operate my microwave oven! Is that the reason? How to remediate? Best regards.
  47. Z

    Why does my food go boom in the microwave?

    Popcorn aside, whenever I put something in the microwave for only a few seconds longer than I probably should have, it pops. I just watched a rib-bone go flying out of its slab, meat spewing everywhere. Is heat responsible for this action?
  48. V

    Microwave's vent close to refrigerator

    < Mentor Note -- Post edited > 1. Homework Statement So do you know how a microwave has air vents on the side? How much of a distance must be allowed between the vent and the side of refrigerator in order for the Microwave not to overheat? Is 10 cm enough? Would putting an aluminum foil on...
  49. P

    Homemade Cosmic Microwave Background detector

    Hi Guys, I studied physics for my bachelor but still I am not a super expert, although I am still working closely to physics (but not so much astronomy). I was wondering if it would be possible to build a radio, or some other devise (any ideas?) that could be tuned at the frequency where the...
  50. G

    What Forces Cause Rotational Emissions?

    I was curious about what forces can be applied to a molecule to cause a rotational emission.
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