ALMA-FEIC Study Group. 2008-05-28
(Last revised 2008-07-16 15:30 UTC)
Front end #1 PAI data: FEND-40.00.00.00-116-A-REP.pdf
band 3 PAI (cartridge #3): FEND-40.02.03.00-133-A-REP.pdf
band 6 PAI (cartridge #3): FEND-40.02.06.00-214-B-TDR.pdf
band 7 PAI (cartridge #1): FEND-40.02.07.00-0010-B-REP.pdf
band 9 PAI (cartridge #1): FEND-40.02.09.00-044-B2-REP+cartridge+acceptance+test+report+SN001.doc
Ticra report (we use efficiency equations on page 118 et seq )
secret document _DO NOT distribute further_ chapter 5 attached
other sections at under appendices 1-11
(This is an EDM reference. Available also in the "Optical Analysis Final Report Chapter 5" below.)
Latest beam scans of bands 3 and 6 using the NSI
scanner after alignment: FEND-40.09.07.00-074-A-REP.pdf
NA FEIC Preliminary Beam Measurements: FEND-40.09.03.00-041-A-REP.pdf
How we analyse data: ALMA-40.00.00.00-123-A-PRO.doc
Block diagram: 20080402_Block+Diagram+of+NA+FEIC+system+without+LORTM.pdf
Test set data
Beam scanner doc
FEIC discussion measurements
Band 6 comparison
2007-10-04 Optical Analysis Final Report Chapter 5
Optics section from FE acceptance (24 MB)
Baryshev beam efficiency presentation
- Far field distances (PDF) or (Excel .xls)
from Richard, who says:
I have made the attached table to show the Rayleigh distances for the ALMA bands.
This assumes a Gaussian beam and a 12 dB taper. The Rayleigh distance is defined as pi*w_02/lambda
with w_0 being the beam waist radius.
CSV and other data from Geoff and others
Data files from Geoff
Geoff's Powerpoint presentation from our 2008-05-27 telecon
Plots of Geoff's data, from Todd
Todd's plots of data with model fits
Fred's FFT of NSI NF data
The first pair of plots is a re-display of the near-field amplitude and
phase as measured by the NSI scanner. The x and y axes are labeled
The second pair of plots shows the amplitude and phase patterns of
a straight FFT of the near-field data. The units for the axes here are
degrees (assuming I computed the grid spacing correctly - which I need
to double check).
The final pair of plots show, for comparison, the far-field distribution
computed by the NSI software, over the range -10 deg to 10 deg.
Todd's plots of Geoff's lambda/4 shifted data, 2007 Scan 13
Todd's plots of Geoff's lambda/4-shifted data, 2008 Scan 20
The above plots are from Geoff's data with lambda/4-shifts, currently
entries 26-37 in the list of data files.
Here are two PDFs, each with six panels, illustrating these 12 data files.
The 2D Gaussian fit parameters are listed under the amplitude panels.
Scan 20 with mask before FFT
In today's meeting, you asked that we compare the FFT of the nearfield
data taken above and below the point in elevation where the anomalous
appearance tends to manifest itself (y > 0.21). In the enclosed plot of
2008_Scan_20, we compare the FFT using the whole data vs. using only the
cleaner area below this line. The right column is simply a zoom of the
middle column. Clearly, there is much less large scale structure when the
top part is masked. Also, note the point-like features at (-34,-33deg) and
(-34,+27deg) which appear more prominently in the unmasked data, and are
nearly symmetric with respect to the beam center ~ (0,-2). I wonder if these could be somehow related to the mechanical
corner struts of the xy stage? However, the scale may not be right for this
to be the case: (200mm)(tan34) = 135mm.
We also examined the FFT of just the upper section of data, and this
showed some of the excess in the upper two quadrants, but with lower S/N.
Scan 20 with complementary mask before FFT
Spreadsheet from Richard Richard says:
Here is a cleaned-up version of my spread-sheet, doing just the spill-over calculation on the Far Field data. On the Scan 77 case that we have been taking as a reference I get 2.91% as the minimum spillover - optimizing just for that - and 3.00% with the secondary at (0, -1.0) deg.
Spreadsheet for phase fitting, from Richard (Excel, 27 MB).
Subreflector patterns, Spreadsheet from Sri.
Subreflector spreadsheet for Scan 77 Sri said:
Attached excel file has subrefl. scattered pattern thru different cuts. The taper at 64 deg. varies from -17 dB at -90 deg. to -11 dB at +90 deg. The 90 deg. plane is the plane of offset of the Band 9 cartridge and the cartridge offset is in the -Y direction (-50mm).
Far field fits summary. Richard says:
I have run through the remaining data sets and put the results in the attached. In some places the consistency of the results in encouraging, in others less so.
- 2008 Scan 20, spurious feature identified (Darrel)
Last revised 2008-06-25
The near-field data of Scan 20 have been filtered to enable identification of the origin of the
spurious far-field feature in this scan already identified from Todd and Fred's analyses.
FTP link to Fred's FFT files. NB, 70+ MB .
or Much smaller version here: jpeg files zipped.
I fft'd the near-field patterns
for Beam 1 and Beam 2 separately, and found that the spurious feature
is much more compact and well-defined in the plots of those data than
in the plots with both beams combined, where it appears more diffuse.
I also noted that for Scan 20 there is a feature at the top and very center
of the the fft plot (actually in these cases, two small blobs slightly
separated), and that in fact there are similar features - at the top for
the 2008 data, and at the bottom for the 2007 data - in every scan.
I think these features are spurious and likely arise from the putative
backlash. I've done the fft for every one of the data sets.
(If you use ghostview to view these, you'll likely see some artifacts
which disappear if you turn OFF ghostview's Antialiasing option.
They may show up with other viewers also, but they don't show
up if you send the file to a printer.)
Scan 4 from 2008 in the near-field phase plot shows very strong
horizontal striations. In my FFT amplitude plot, note the intensity
of the pink blob at the very top.
I should mention that in the fft plots the coordinates on the
plots now are u and v. (Richard had questioned me and Geoff on
Calculation of efficiencies revised 2008-06-22 from Richard Hills (PDF) or Word .doc format.
Beam efficiency Spreadsheet 2007 7.xls Modified spreadsheet from Richard Hills
fit-all-2007_small_A.xls Richard's spreadsheet on the same data
Richard describes the above two spreadsheets:
I put in the 0.1-degree resolution data that you [Josh] sent and got the
sheet working. There were still some discrepancies with my numbers so I
had a poke around and found a few problems. I have marked them and made
modifications. This now agrees with my sheet for the particular set of
numbers that have been assumed for the phase centre. (I haven't tried
to figure out how the macros work.)
If you fit for the best phase centre the phase efficiency increases from
0.9920 to 0.9953. More importantly the phase centre shifts by a further
(0.38,1.69,-24.22). To me this says that we do need to do a proper
fit if we are to use these values to anything secure about beam squint, etc.
Patterns and efficiencies at 94 GHz from Sri. Sri said:
Josh gave me data on Band 3 Scan 17. I used Polarization 1 data to calculate the subreflector scattered pattern and the telescope beam. Since, setting up the geometry for Band 3 is complex, I first did my calculations with the Band 3 window on axis of the telescope. So for this case the subreflc. is not tilted. Then I did the Band 3 actual case where the window is off set by 18.1 cms and the subreflector is tilted by 0.881 deg.
Summary, Band 3 Scan 17 (Word)
There are 4 exl files.
In 94P1efm.xl the patterns for on axis and off axis are overlaid on a single graph. The Off case beam looks good and there is only 1.1% loss for this case.
- 94P1abs.xls Subrefl pattern for window on axis
- 94P1abm.xls Telescope beam for window on axis
- 94P1efs.xls Subrefl pattern for window off axis
- 94P1efm.xls Telescope beam for window off axis.
Josh compilation of
data in accordance with the list Geoff gave.
The list is included.
Comments from Darrel on the necessary sampling interval
for near-field beam scanner. 0.4*lambda is a good value.
Beam Efficiency Spreadsheet Revised 2007 17.xls Richard commented:
edited the scan 17 version to have names consistent with the TICRA
report and the revised version of my note.
Josh has put the current band 3 scan results
here as a spreadsheet. Josh will update this sheet as more data become available.
Geoff supplied 4 new data files:
[I attach] the files for the scans 100 and 109 (each was at two z's so I
send both scans separately - not combined)
100 is WITH the warm optics
109 is WITHOUT warm optics - I scanned the same area so I missed the peak.
The values are normalized to the peak value seen in the scan area. For
109 the peak in area is -60.2 dBm. When I went to the signal maximum it
has -28.2 dBm ( so everything is 32 dB down or more)
(The peak in scan 100 is -26.49 dBm)
Geoff added plots of the above scans:
Geoff said of the above files:
- NF scans 100 & 109 (.xls) . NB large, ~11 MB file .
- Darrel created a smaller, PDF version of the large xls file:
NF scans 100 & 109 (.PDF file)
Geoff also gives details of the feed horns used as sources:
Source feed horns (.doc file) .
I attach plots of the 4 scans I sent earlier.
The values are normalized to the peak value seen in the scan area
(thanks to the NSI software). For 109 the peak in area is -60.2 dBm.
When I went to the signal maximum it has -28.2 dBm ( so everything is 32
dB down or more -the light red being another 10-12 dB down = -42dB)
(The peak in scan 100 is -26.49 dBm)
There is some change with z distance.
I also attach details on the feed horns used on the sources for the
Comments and questions from Richard, July 4th
Source feed horns comments
Item list plus interchanges
Some earlier correspondence from Bernard Lazareff
- another 2008-02-21
Notes from 2008-07-11 telecon
First version of Baryshev report from Geoff - still missing quite a few sections and any useful numbers.