Differences between revisions 14 and 16 (spanning 2 versions)
Revision 14 as of 2012-12-06 05:01:27
Size: 1450
Comment:
Revision 16 as of 2021-06-08 17:57:55
Size: 1373
Comment:
Deletions are marked like this. Additions are marked like this.
Line 21: Line 21:
<<EmbedObject(a4d21.swf,play=true,loop=true,width=1024,height=768)>> {{ a4d21.png | | height=768 }}
Line 28: Line 28:
<<EmbedObject(a4d21-16.swf,play=true,loop=true,width=1024,height=768)>> {{ a4d21-16.png | | height=768 }}
Line 32: Line 32:
MORE LATER MoreLater

Array Phasing

When we randomly dither the position of the emitters in a 3 dimensional phased array, it smears out the grating lobes. I am looking for a better function.

A position dither function to try:

D = L/2

k = 2 \pi / N * L

\Delta x = D * ( \sin( k z ) + \cos( k y ) )

\Delta y = D * ( \sin( k x ) + \cos( k z ) )

\Delta z = D * ( \sin( k y ) + \cos( k x ) )

... or some variation of that ( I originally tried D = \lambda/2 , with little effect). This assumes the spacing L >> \lambda , a sparse array, so that the antennas do not couple (much). Try scaling D and k, and also modifying amplitudes across the array like a Hamming window, and see how that changes the sidelobes.

This happens on top of the array of perhaps hundreds of emitters on the thinsat itself, which beamforms to a few degrees of angle, reducing power splattered far from the target.

The signal is broadband, so there is not a well defined \lambda . We may end up making k a function of x, y, and z as well.

5x5x5 skewed, dithered array

a4d21.png

Annotated version with explanation coming soon.

16x16x16 skewed, dithered array

a4d21-16.png

Annotated version with explanation coming soon.

MoreLater

ArrayPhasing (last edited 2021-06-08 17:57:55 by KeithLofstrom)