Hi,
What does the dielectric lens do in dual feed?
73 de Ismo
Hi,
What does the dielectric lens do in dual feed?
73 de Ismo
I assumed everyone knew this but perhaps I am wrong. A lens has a different refractive index to air so it bends electromagnetic radiation, thereby shaping the beam. https://en.wikipedia.org/wiki/Lens_(optics)
In my dual band feed it narrows the beamwidth compared to the open waveguide. It also transforms the impedance to provide a better match - the rear of the lens inside the waveguide is about matching, the bit outside is doing the beam shaping.. The narrower beam is needed to better match an antenna with a longer focal length. The open waveguide would be OK for a F/D of 0.3 - a deep dish, but with a typical satellite dish the F/D is 0.6 so much of the radiation would miss the reflector. This both reduces gain and picks up more ground noise.
Lenses can also be used as antennas, the lens horn for example is acting just like a magnifying glass focusing the sun.
This Twitter post shows it well https://twitter.com/HHolsink/status/1131596061703909376
Mike
Yep, nr2 had equal performance compared to my rocket LNB and gave the highest SNR with my contraption.