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# Swept-Beam Frequency-Multiplier

Sweep an Electron Beam Along a Linear Array of Apertures
 (+1) [vote for, against]

To illustrate the principle, imagine a hollow metal disc suspended in a vacuum. The outer (curved) surface of the disc is perforated in a line extending maybe one third around it's circumference with small holes. These holes are spaced by a distance equal to or less than their diameters.
In the center of the disc, is an electron beam source aimed toward the middle hole. There is a deflector plate on both sides of the beam.
In operation, the beam is repeatedly swept along the line of holes. The pattern of holes cause the portion of the beam escaping the disc to be modulated, generating radio waves at a frequency equal to the sweep frequency times the number of holes.
For low sweep frequencies, designing the devices would be relatively easy. Since this is intended as a way to multiply our highest achievable frequencies even further, there would be major concerns over wave propagation and interference. For example, at very short wavelengths, a wave being generated near one hole could lag too far behind or ahead of that from the next hole.
Also, at our "highest achievable" frequencies, it follows that we would not be able to generate them with the sawtooth waveforms customary for beam deflection, since that would require harmonics (even higher frequencies) to be generated.
If one is limited to sine waves for beam deflection, he would need to continuously vary the size, shape and spacing of the holes, in proportion to the instantaneous amplitudes along a sine curve, to precompensate for the nonlinearity.

One could go a step further and have a two dimensional array of holes, but have some holes missing in each line (except for one), in a pattern corresponding to binary numbers 0 through 255. This could be used as the basis for a binary transmitter. It wouldn't be as efficient for encoding data as the standard QAM (Quadrature Amplitude Modulation), since it would lack bit-stacking and would only modulate a single signal parameter (amplitude).
 — Alvin, Dec 10 2016

wheely slot look thorugh movie thing might be called Zoetrope https://en.wikipedia.org/wiki/Zoetrope
[beanangel, Dec 10 2016]

Somehow, this idea reminded me of this almost-completely-unrelated thing. [Wrongfellow, Dec 13 2016]

2d moire of squares, where the Near field # divides the far field # lines, the frequency is higher than either, I think, possibly http://www.eldo.us/...ain-link-mockup.jpg
[beanangel, Dec 13 2016]

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 um, this might not make sense, but you might like it anyway. consider a ceiling fan reflected in a spoon, at parts of the spoons curvature the fan blades pass slowly, blooop bloooop, then at an area (near the neck) of different curvature perhaps they seem to pass faster than the actual fan blades. so would it be possible to use an optical element (even an EM element like an old CRT EM system or electron microscope focuser) to just magnify or shrinkify an EM beam to have higher sweep frequency? The photons, or EM reflected off the thingy are actually sweeping at different frequencies.

 I used to wonder if it was possibly heighten frequency with a rotator to say turn green light to blue.

also, I am completely confused yet this reminds me of an old movie kind of thing, the "wheely slot look through movie thing" that might be called a Zoetrope If it similar enough, the wikipedia thing on zoetrope mentions that 3D zoetropes are possible, so if it works with EM, then you could make 3D EM blobs
 — beanangel, Dec 10 2016

 Like [beanangel] I'm thinking a small height cylinder with holes, with an outward beam. I maybe wrong.

Is it possible to have a fixed beam through an 'electonic hole' ? If a material could open and close equal or faster than the speed of beam deflection then this setup would be the same. Hole size and speed would be much more flexible than the physical hole, to do the binary modulation.
 — wjt, Dec 10 2016

@beanangel,
It would definitely be preferrable to use electron optics to pre-compensate for a sine wave deflection signal.

"I used to wonder if it was possibly heighten frequency with a rotator to say turn green light to blue."

You'd have to spin the rotator awfully fast for that much of a wavelength reduction.

@wjt,
"Like [beanangel] I'm thinking a small height cylinder with holes, with an outward beam...."

I keep getting the feeling that one or both of you are thinking of using an external signal to modulate the beam. That though, would (at best) only amplify that external signal. The basic idea is to begin with our highest achievable frequency and use it as a deflection signal to achieve an even higher frequency.

Rotating the disc would also modulate the beam, but couldn't produce frequencies as high as with electronic means of deflection.
 — Alvin, Dec 11 2016

 this might possibly work, yet it might not. You have heard of a beat frequency, where layering two ||||||||| over each other causes a periodic nodal area more gradual than either frequency. That is at 1D though, if you overlap a network of squares, then make a moire (# on #) I think I noticed that the spacing of the predictable overlaps is actually smaller than the length of the sides. Layering squares actually produces something faster than either frequency (square side length), and you can draw and angled line through these to create the largest amount of pulsed heightened frequency.

also, another thing to think about when heightening frequency is that if you look at a # (square grid) at an oblique angle the lines look more closely spaced, so changing a viewing angle can change the "functional" frequency
 — beanangel, Dec 13 2016

The link posted by Wrongfellow makes it obvious this is old technology. That's a great website. Thanks for all of the input.
 — Alvin, Dec 14 2016

Electronic equivalent of an acoustic siren [+]
 — notexactly, Apr 19 2018

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