Phased array of dishes

Corey · #1 (**permalink**) 03-22-2007, 07:12 PM

I'm wondering if anyone here has experimented with ganging together two or more small dishes, mounted in the same plane, and then use some sort of device to add their signals together as an input to the receiver. Basically a phased array.

I know it would be a lot of trouble to build, but it would definitely be unique looking, and should give maybe 3db gain plus a narrower main lobe, especially of the dishes were separated in space by any significant distance.

wejones · #2 (**permalink**) 03-22-2007, 07:48 PM

Quote:

Originally Posted by Corey

I'm wondering if anyone here has experimented with ganging together two or more small dishes, mounted in the same plane, and then use some sort of device to add their signals together as an input to the receiver. Basically a phased array.

I know it would be a lot of trouble to build, but it would definitely be unique looking, and should give maybe 3db gain plus a narrower main lobe, especially of the dishes were separated in space by any significant distance.

Interesting topic. At lower frequencies, you can get the phase right by trimming the length of the feed lines, but that would be quite a feat for something with this small of a wavelength. But it would be fun to try.

I'm not so sure about the separation in space affecting the main lobe thing though. That seems intuitive, but the equations I've seen suggest that the resolution is dependent only on the gain, however the equations I had were based on astronomy, which is different from a point source, so you may be right.

Corey · #3 (**permalink**) 03-22-2007, 08:58 PM

I know that radio telescopes use long baseline interferometry, which is a fancy way of saying "phased array" to get the angular resolution effect of a dish as wide as the baseline, but obviously far less gain.

Corey · #4 (**permalink**) 03-28-2007, 08:12 PM

After thinking about this further, I've found that it's not doable with two dishes using LNBF's. This is because the LO's of the two dishes would not be in phase or even at the same exact frequency, so the dishes cannot be phased together with a simple combiner (of some sort).

It would be possible if there were no LO and mixer, but then you'd be working with 12 GHz signals over lossy cables instead of ~2 GHz signals, and you'd still need a block converter.

Anyway, as Emily Latella might have said, "Nevermind!"

siliggy · #5 (**permalink**) 06-13-2008, 06:35 PM

Quote:

Originally Posted by Corey

Anyway, as Emily Latella might have said, "Nevermind!"

You guys up north give up too easy do you?
Has anyone else played with this idea since these posts?
Have a look down south at these interesting failures:
Can multiple dishes be used to increase signal - Page 2 - Free to Air Satellite Forums (Asia Pacific)

and at the bottom of this page:

The Grail - Page 6 - Free to Air Satellite Forums (Asia Pacific)

Corey · #6 (**permalink**) 06-14-2008, 02:12 AM

Quote:

Originally Posted by siliggy

You guys up north give up too easy do you?
Has anyone else played with this idea since these posts?
Have a look down south at these interesting failures:
Can multiple dishes be used to increase signal - Page 2 - Free to Air Satellite Forums (Asia Pacific)

and at the bottom of this page:

The Grail - Page 6 - Free to Air Satellite Forums (Asia Pacific)

Great links! Looks like someone actually tried this

I didn't think of using wave guides to feed a single LNB. Good thinking on that one.. it gets around the problem of the LNBs being out of sync, but does require some "creative plumbing".

Jim-S · #7 (**permalink**) 06-14-2008, 06:38 AM

Too deep for this northern.
Jim

siliggy · #8 (**permalink**) 06-15-2008, 04:48 AM

Quote:

Originally Posted by Corey

Great links! Looks like someone actually tried this

I didn't think of using wave guides to feed a single LNB. Good thinking on that one.. it gets around the problem of the LNBs being out of sync, but does require some "creative plumbing".

I'm thinking of using the dish "with a hole in it" as a combiner by putting another hole in the other side. Then the three dishes in combination would be tinkered with to attempt DX reception of a target transponder. Another bloke on our forum has just found an ideal weak "out of footprint" signal for me to test with. He can just just get the Ku signal with a 2.3M dish. So If I can get it with three 0.65-0.80M dishes that would be a real good test for the w'hole' idea.