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BaseBand Configurations

In the panel BaseBand Configurations up to four baseband configurations can be defined. An overview of the upper part of this panel is provided in Figure  8.10 . A number of fields for specifying the basebands and their spectral windows are described below. More details can obtained in the OT Reference Manual.

This panel contains a summary table of the baseband configurations; it lists the name, center rest frequency, data products and sideband separation, the LO2 frequency and the data rate for each of the basebands. Just above this is the LO Setup Preferences panel that can be used to calculate the LO frequencies. Depending on how many baseband configurations have been defined, the LO Setup Preferences subpanel can be used for optimising the position of the frequency band by adjusting the LO1 and LO2 settings. In the Sideband(s) to priotise check boxes the user can indicate the priority for the USB and LSB. Below there are check boxes for each of the base bands in which the user can enter a weight between 0 and 100 to priorities these base bands for calculating the LO1 frequency. Pressing the Calculate LOs button will calculate the LO setup according to the entered parameters.

The best setup, in terms of LO1 (and LO2) settings for a single or multiple baseband configuration is determined by calculating the error between the ideal and the adjusted LO2 settings for each of the basebands and minimising the sum of these errors. After clicking on the Calculate LOs button, a summary of the optimisation results can be seen in the pane, using the Information tab. Clicking on the expansion symbol \( >> \) will provide you with the details, including the ideal setting of the LO1 and LO2 frequencies, the frequency offsets given the system limitations in setting the LO2 frequencies and the adjusted LO1 and LO2 frequencies. After the optimisation is done, the results are visible in the LO1 Frequency fields. Also visible is the expectedtotal data rate.

Figure 8.10: The fields for defining the baseband Configurations.
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LO Configuration is also supported by the LO Configuration Tool via Tools $\rightarrow$ ALMA LO Configuration Tool . This is an experimental tool that runs on a separate window and is also intended for expert users. It implements the same algorithm which will be used in the Control subsystem that will set the LO settings during the actual observations. For details see Section  5.3 .

In the BaseBand Configurations panel there is also an advanced Engineering sub panel.The user must click on the Engineering Set-up button to enable this sub panel. After doing so the user can enter values for the FLOOG , enable/disable Tune High and the LO1 Frequency value directly. Enabling the engineering set-up also has the effect of making the Center Freq (Rest) column read-only and the LO2 Frequency writable in the base band table.


next up previous contents index
Next: Baseband Specifications Up: Instrument Setup Previous: Correlator Configuration   Contents   Index
The ALMA OT Team, 2011 May 20