polarization rotation - Page 1
Forum section: electronics / rf-microwave

author: aholtzma
author_rank: Contributor
timestamp: June 15, 2023, 06:42:35 pm
content: I came across a mention of a broadband polarization rotation material in the marketing materials for the AU600 antenna from R&S:https://cdn.rohde-schwarz.com/magazine/pdfs_1/article/213/english_11/NEWS_213_AU600_english.pdfIn the attached photo, the polarization rotation material is the thing that looks like a HEPA filter.Does anyone have any references or wild ideas on how this works? The Faraday Effect is used in optics for polarization rotation but needs a strong magnetic field.

author: radiolistener
author_rank: Super Contributor
timestamp: June 15, 2023, 10:46:53 pm
content: this is not HEPA filter, here is a quote:QuoteSo, this is some kind of polarization filter. Probably made frommetamaterialswith specific electromagnetic properties which allows to rotate wave polarization.It's properties defined not by material properties, but by complex 3D mesh structure of many oscillators, so they all together produce desired effect on electromagnetic wave. It's principle in some kind similar toPESA/AESAantennas.

author: switchabl
author_rank: Frequent Contributor
timestamp: June 17, 2023, 10:23:18 am
content: It's basically just a series of concentric wire grid polarizers (I guess you could technically call those a metamaterial but I think most people wouldn't). The wires are horizontal on the outermost layer, vertical on the innermost layer and are oriented at varying angles inbetween. It is similar to what is sometimes called the three polarizer "paradox".It is simple to make and inherently broadband which (resonant) chiral metamaterials aren't. The main disadvantage is that it is lossy.Patent:https://worldwide.espacenet.com/patent/search?q=pn%3DEP2493019B1

author: aholtzma
author_rank: Contributor
timestamp: June 18, 2023, 03:30:04 am
content: Thanks! This application really makes it clear how the three polarizer paradox works. I'm surprised the patent is so recent, they must have been making these well before then.

author: profdc9
author_rank: Frequent Contributor
timestamp: June 18, 2023, 05:32:19 am
content: A helical wire produces more retardance for the circular polarization that twists in same rotation as the wire, and less retardance for the circular polarization that twists in the opposite rotation. This effect at optical frequencies is called "optical activity" and occurs with chiral molecules (the example often being used is a solution of dextro-glucose, or dextrose, which is preferentially synthesized by plants). However, the same thing can occur for dielectrics or conductors that are chiral in the RF. For example a helical antenna preferentially transmits and receives left or right circular polarization, but not both.The chirality effect (due to a helical dielectric) and the Faraday effect (a magnetic effect due to electric currents moving in circles) are different, in that the chirality effect has time-reversal symmetry and the magnetic effect does not have time-reversal symmetry. This is because the Faraday effect requires a permanent magnetic field which is created by magnetic dipoles which can be modeled by current loops. The movement of the current in the loop breaks time-reversal symmetry, as viewed backwards in time, the current in the loop travels in the opposite direction. This is why the Faraday effect can be used for optical isolators.

author: coppercone2
author_rank: Super Contributor
timestamp: June 18, 2023, 06:08:30 pm
content: i strongly recommend looking at animations for the time stuff because it really clears it up when you see things rotate. I was rotating my fingers for a while and got it but a video is far easier. (when I was trying to understand someones explanation about circulators).ever wish your hand or head could be detachable? If you can leave your head whereever you want, all the things with relativity might be alot easier, if you can observe yourself doing things.Whats the last thing the french politician understood? The theory of relativity.