Allowed "multiple regions modes" for the ALMA bilateral correlator

  • Multiple region mode allows one to define multiple windows of equal bandwidth that can be placed anywhere in the 2 GHz baseband. See ALMA Memo 556. These are the ten supported combinations:

Total BW Number of regions * Bandwidth of region
2 GHz not supported
1 GHz 16*62.5 MHz 8*125 4*250 2*500
500 MHz 8*62.5 4*125 2*250  
250 MHz 4*62.5 2*125    
125 MHz 2*62.5      
<125 MHz not supported      

  • The corresponding velocity widths in the different bands are given below. This takes into account the 6.25% overlap required (which reduces the total velocity width) when multiple 62.5 MHz windows are combined to produce a broader window.
  • All the filters are individually tunable, so you could play "mix-and-match". For instance, in the 1-GHz bandwidth modes, you could use one quadrant to observe 8 * 62.5 MHz regions and 1 * 500 MHz.

Number of windows per baseband: 2 4 8 16
Number of windows in 4 basebands: 8 16 32 64
Band Frequency (GHz) 500 MHz 250 MHz 125 MHz 62.5 MHz
3 100 1406 km/s 703 351 187
4 150 938 468 234 125
5 183 769 384 192 102
6 230 611 306 153 82
7 345 408 204 102 54
8 460 306 153 76 41
9 690 204 102 51 27
10 810 173 87 43 23
-- ToddHunter - 2010-12-09
Topic revision: r3 - 2011-06-10, ToddHunter
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