Receivers

All antennas are equipped with dual polarization receivers for the 3mm, 2mm, and 1.3mm atmospheric windows. The frequency range is 80GHz to 116GHz for the 3mm band, 129GHz to 174GHz for the 2mm band, and 201 to 267GHz for the 1.3mm band.

	Band 1	Band 2	Band 3
RF range$^*$	80-116	129-174	201-267
$\rm T_{rec}$ LSB	40-55	30-50	40-60
$\rm T_{rec}$ USB	40-55	40-80	50-70
$\rm G_{im}$/[dB]	-10	-12 ... -10	-12 ... -8
RF LSB	80-104	129-168	201-267
RF USB	104-116	147-174

$^*$ center of the 4-8GHz IF band

Each band of the new receivers is dual-polarization with the two RF channels of one band observing at the same frequency (common LO). The different bands are not co-aligned in the focal plane (and therefore on the sky). The mixers are single-sideband, backshort-tuned; they can be tuned USB or LSB, both choices being available in the central part of the RF band. The typical image rejection is 10dB. Each IF channel is 4 GHz wide (4-8 GHz). Only one frequency band can be connected to the IF transmission lines at any time. Because of this reason and due to the pointing offsets between different frequency bands, only one band can be observed at any time. One of the two other bands is in stand-by mode (power on and local oscillator phase-locked) and is available, e.g., for pointing. Time-shared observations between different frequency bands can not be offered yet.

The two 4 GHz wide IF-channels (one per polarization) are transmitted by optical fibers to the central building. At present, the 4GHz bandwidth can be processed only partially by the existing correlator, through a dedicated IF processor that converts selected 1 GHz wide slices of the 4-8 GHz first IFs down to 0.1-1.1 GHz, the input range of the existing correlator. Further details are given in the section describing the correlator setup and the IF processor.