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About Basebands, SideBands and
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About Basebands, SideBands and
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The positions of the upper and lower sidebands (USB and LSB) within the ALMA Receiver Bands are determined by the choice of the first Local Oscillator (LO1) setting. The bandwidth of each sidebands is 4 GHz for 2SB receivers (bands 3-8) and 8 GHz for SSB (bands 1 and 2) and DSB (bands 9 and 10) receivers. The central frequencies of the sidebands are separated from the LO1 frequency by this bandwidth. In order to fully use both sidebands, the value of LO1 must be separated from the edge of the ALMA receiver band by this bandwidth
.
For each science or calibration Target, the user can specify up to four basebands. Hence, within the selected ALMA receiver band it is possible to observe in four basebands simultaneously. The central frequency of each of these basebands is determined by LO1 and the frequency setting of a second local oscillator (LO2). All basebands can be placed in either the LSB or the USB or two can be in each sideband. Since the system provides only limited choices for the LO2 frequencies, obtaining the requested central baseband frequency for each baseband requires the right combination of LO1 and LO2.
Next:
Spectral Windows
Up:
About Basebands, SideBands and
Previous:
About Basebands, SideBands and
Contents
Index
The ALMA OT Team, 2011 May 20