|
Size: 709
Comment:
|
Size: 1065
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 $ $ \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 ) ) $ |
||<:-3> $ D = \lambda/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 16: | Line 12: |
| We can scale D and k, and also modify amplitudes across the array like a Hamming window, and see how that changes the sidelobes. | 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. |
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 = \lambda/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. 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.
MORE LATER