Differences between revisions 2 and 13 (spanning 11 versions)
Revision 2 as of 2012-11-30 05:35:43
Size: 714
Comment:
Revision 13 as of 2012-12-06 04:54:27
Size: 1147
Comment:
Deletions are marked like this. Additions are marked like this.
Line 6: Line 6:
A smear function to try: A position dither function to try:
Line 8: Line 8:
$ D = \lambda/2 $
$ k = 2 \pi / N * L $
||<:-3> $ D = L/2 $ ||<:-3> $ k = 2 \pi / N * L $ ||
|| $ \Delta x = D * ( \sin( k z ) + \cos( k y ) ) $ || ||<-2> $ \Delta y = D * ( \sin( k x ) + \cos( k z ) ) $ || || $ \Delta z = D * ( \sin( k y ) + \cos( k x ) ) $ ||
Line 11: Line 11:
$ \delta x = D * ( \sin( k z ) + \cos( k y ) ) $
\
$ \delta y = D * ( \sin( k x ) + \cos( k z ) ) $
... 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.
Line 15: Line 14:
$ \delta z = D * ( \sin( k y ) + \cos( k x ) ) $ 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.
Line 17: Line 17:
... or some variation of that. This assumes the spacing $ L >> \lambda $, a sparse array, so that the antennas do not couple (much).
We can scale D and k, and also modify amplitudes across the array like a Hamming window, and see how that changes the sidelobes.
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 array ==


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 array

MORE LATER

ArrayPhasing (last edited 2022-03-15 01:37:15 by KeithLofstrom)