4 ms·
It could be a zone plate. They look similar, but focus based on diffraction instead of refraction. https://en.wikipedia.org/wiki/Zone_plate https://en.wikipedi
by tropo 7y ago
It could be a zone plate. They look similar, but focus based on diffraction instead of refraction.
https://en.wikipedia.org/wiki/Zone_plate https://en.wikipedia.org/wiki/Zone_plate
The diagram could be either, but isn't a perfect match for either. Perhaps a hybrid is possible. The 4-level right-angle construction (stair step) is weird.
- new299 7y agoThe Zone plates are very cool. Thanks for the link.
- dreamcompiler 7y agoZone plates work great for radio waves. I don't know why they aren't used more than parabolic dishes, since they're easier to manufacture and mount. Perhaps the gain is smaller for a given diameter?
- burfog 7y agoA third choice is the phased array. There are two dimensions to focus, and they don't have to be done the same way. For example, the trough antenna is parabolic in one direction but uses something else in the other direction. Viewed from along the resulting beam, it is a rectangle. Manufacture the reflector involves a simple 1-dimensional bend of the metal.
- consp 7y agoMy guess would be twofold: adding delay if the source is not straight though enough to screw communication or diffusing the image too much if your focal point is not a point but a sensor.
- dTal 7y agoZone plate focal length is wavelength dependent, unlike parabolic dishes.