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: http://www.naic.edu/~astro/techinfo/iflo/iflo_1500.shtml
Дата изменения: Unknown Дата индексирования: Sat Dec 22 10:37:42 2007 Кодировка: Поисковые слова: arp 220 |
Determining both where to place the local oscillators (LOs) and through which IF filter path to send the signal of interest is not trivial. Below is both a graphical description of the signal conversion which occurs in taking the signal of interest down the 1.5 GHz and a description of the algorithm used by the telescope control gui to choose which IF/LO set-up to use for an observation.
The graphic below shows an example of the down conversion path used in the 1-2GHz IFLO path:
To choose which IF path to take as well as where to place the LO (high or low side), we've developed an algorithm for the telescope control gui to follow.
Definitions:
The Algotrithm:
Check to see if the high option gives an LO frequency which lies within another subcorrelator band above the subcorrelator of interest. If it does not, then use the high option.
If the high option does give an LO frequency which lies within another subcorrelator band above the subcorrelator of interest, then check if the low option gives an LO frequency which lies within another subcorrelator band below the subcorrelator of interest. If it does not, then use the low option.
If neither choice is any good, pick the option which keeps the LO the farthest from the center band of any other subcorrelator.