Electronics > RF, Microwave, Ham Radio

Laser-like narrow cone of Mhz/Ghz waves?

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cape zoloh:
Compare a flash light and a laser pointer aimed at a wall 10meters/30 feet away. We would see a small diameter dot from the laser and from the flash light, a very large diameter circle illuminating the wall.

How laser-like could you make a microwave or millimetre-wave in the sense that it would only hit a very small area, concentrated into a small dot on the sensor or whatever device the measuring uses.

I've heard the word "maser" but I don't know if that has any relevance here.

I hope I gave sufficient description of what my question is. (-How small diameter can you make a EM "beam" OR -Is transmitting a "beam" of electromagnetism with a very small cross section area, like a laser, possible?)

first guess would be, that it depends from the aperture of the antenna; if we talk about 10-100GHz, the aperture on such frequencies is quite small already due to the used high gain antennas (horn antennas or parabolic dishes for example); in the practical world, as hamradio operator you have to align your GHz-setup quite accurately, within an angle of 2-3° or less to hit the beam of your counterpart
but after all, I don't see real ways to focus a GHz-beam in the manner you can do it in the spectrum of light with a laser.

The only difference between ligyt and radio waves is wavelength. The physics of Gaussian Beams are the same: https://en.wikipedia.org/wiki/Gaussian_beam

Depends on the ratio of the beam aperture to the wavelength in question among other things.

This is why free space laser doings over significant distances (Like say hitting that reflector on the moon) generally start off with a reverse telescope because the beam starting out say a meter in diameter will diverge much less then one starting out 1mm in diameter all things being equal. 

Figure high microwave as a few mm wavelength, and visible light as a few hundred nm wavelength, so the aperture for the microwave emitter needs to be about 10,000 times the aperture of the optical emitter to obtain the same far field divergence.

End of the day they are both EM waves, so the same optical principles apply to both.

This should answer your question:

The wave nature of light, radio waves or sound waves are pretty similar in that respect for a single source.
With microwaves you can also use a phased array and have a larger virtual source aperture to play with.


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