4 ms·

I wonder if there are materials of one-way reflectance so that all of the sphere would be used instead of a particular face. Why would this be used over a phas

by adolph 3y ago

I wonder if there are materials of one-way reflectance so that all of the sphere would be used instead of a particular face. Why would this be used over a phased array where the paraboloid shape is created in software post-processing?

mikewarot 3y ago
It's not the sphere that does the work, it's the parabola inside it, cutting it in half.
ben_w 3y ago
One-way reflectance isn't a really real thing in physics, the closest you get is the illusion from having a bright room and a dark room on opposite sides of a mostly-reflective boundary. https://en.wikipedia.org/wiki/One-way_mirror https://en.wikipedia.org/wiki/One-way_mirror
- nomel 3y ago
  If you give me a polarized wave, I can give you a surface that reflects in one direction, and passes in the other, with awful efficiency. ;)
itishappy 3y ago
It wouldn't help. Focusing requires a concave surface, and the inside of the sphere is the only concave bit. Coating the outside would create an omnidirectional reflector, but it'd be super low-gain. We actually tried exactly this with Project Echo. https://en.wikipedia.org/wiki/Project_Echo https://en.wikipedia.org/wiki/Project_Echo Also, "one-way reflectance" is largely a myth. One-way mirrors in police stations and stores are actually just partially reflective mirrors with a dark room on one side. A true one-way reflector would involve an optical circulator, which tends to be a small, sensitive, expensive component, not something you can coat over a flexible surface. https://en.wikipedia.org/wiki/Optical_circulator https://en.wikipedia.org/wiki/Optical_circulator Lastly, the main advantage is cost and simplicity. Phased arrays use fancy semiconductors. This gives you a lot of features and benefits, but comes at significant cost. This antenna is more or less a Mylar party balloon, it would not surprised me if it's orders of magnitudes cheaper.

by adolph 3y ago

mikewarot 3y ago

It's not the sphere that does the work, it's the parabola inside it, cutting it in half.

ben_w 3y ago

One-way reflectance isn't a really real thing in physics, the closest you get is the illusion from having a bright room and a dark room on opposite sides of a mostly-reflective boundary. https://en.wikipedia.org/wiki/One-way_mirror https://en.wikipedia.org/wiki/One-way_mirror

nomel 3y ago
If you give me a polarized wave, I can give you a surface that reflects in one direction, and passes in the other, with awful efficiency. ;)

itishappy 3y ago

It wouldn't help. Focusing requires a concave surface, and the inside of the sphere is the only concave bit. Coating the outside would create an omnidirectional reflector, but it'd be super low-gain. We actually tried exactly this with Project Echo. https://en.wikipedia.org/wiki/Project_Echo https://en.wikipedia.org/wiki/Project_Echo Also, "one-way reflectance" is largely a myth. One-way mirrors in police stations and stores are actually just partially reflective mirrors with a dark room on one side. A true one-way reflector would involve an optical circulator, which tends to be a small, sensitive, expensive component, not something you can coat over a flexible surface. https://en.wikipedia.org/wiki/Optical_circulator https://en.wikipedia.org/wiki/Optical_circulator Lastly, the main advantage is cost and simplicity. Phased arrays use fancy semiconductors. This gives you a lot of features and benefits, but comes at significant cost. This antenna is more or less a Mylar party balloon, it would not surprised me if it's orders of magnitudes cheaper.