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 at 2mm, and 201GHz to 267GHz for the 1.3mm band.
Each frequency band of the receivers is dual-polarization with the two RF channels observing at the same sky frequency. The mixers are single-sideband, with a typical image rejection of 10dB. Only one frequency band (dual polarization) can be connected to the IF transmission lines at any time. Because of this reason and due to pointing offsets between different frequency bands, only one band can be observed at any time. One of the other bands is in stand-by (power on and local oscillator phase-locked) and is available, e.g., for pointing and focusing. Time-shared observations between frequency bands is possible, though not very efficient.
The two IF-channels (one per polarization), each 4GHz wide, are
transmitted by optical fibers to the central building. The new
wide-band correlator WideX is able to process both 4GHz
wide IFs simultaneously with a fixed spectral resolution of about
2MHz. The narrow-band correlator, on the other hand, can process
the 4GHz bandwidth only partially, but with spectral resolution up
to 39kHz. A dedicated IF processor converts selected 1GHz wide
slices of the 4-8GHz first IFs down to 0.1-1.1GHz, the input range
of the narrow-band correlator. Further details are given in
Section .
Band 1 | Band 2 | Band 3 | |
RF coverage | 80-116 | 129-174 | 201-267 |
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40-55 | 30-50 | 40-60 |
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40-55 | 40-80 | 50-70 |
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-10dB | -12 -10dB | -12 -8dB |
RF range LSB | 80-104 | 129-168 | 201-264 |
RF range USB | 104-116 | 147-174 | 264-267 |