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Receivers

All antennas are equipped with dual polarization receivers for the 3 mm, 2 mm, 1.3 mm, and 0.8 mm atmospheric windows. The frequency ranges are 80 GHz to 116 GHz for the 3 mm band, 129 GHz to 177 GHz for the 2 mm band, 201 to 267 GHz for the 1.3 mm band, and 277 to 371 GHz for the 0.8 mm band.

Each receiver band has dual-polarization capabilities with the two RF channels, one per polarization, observing at the same frequency. The four different bands are not co-aligned in the focal plane (and therefore on the sky). Due to the pointing offsets between the different frequency bands, only one band can be observed at any time. One of the three 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 RF bands (e.g., band 1 and band 3) are possible in well justified cases, they are however not very efficient.

The mixers for bands 1, 2, and 3 are single-sideband, backshort-tuned; they will usually be tuned LSB, except for the upper part of the frequency range in all three bands where the mixers will be tuned USB. The band 4 mixers are 2SB receivers, operated in single-sideband mode (SSB). They can be tuned LSB or USB throughout most of the accessible frequency range. The typical image rejection is 10 dB (20 dB for band 4). Each IF channel is 3.6 GHz wide (4.2-7.8 GHz).

The two IF-channels (one per polarization), each 3.6 GHz wide, are transmitted by optical fibers to the central building.

The wide-band correlator WideX is able to process both 3.6 GHz wide IFs simultaneously with a fixed resolution of about 1.95 MHz. The narrow-band correlator can process the two 3.6 GHz wide IF-channels (one per polarization) only partially. A dedicated IF processor converts selected 1 GHz wide slices of the 4.2-7.8 GHz first IFs down to 0.1-1.1 GHz, the input range of the narrow-band correlator. Further details are given in Sect.[*] describing the correlator setup and the IF processor.


Table: Receiver specifications. The tuning ranges refer to a centering of the respective sky frequency at the center of the IF band at 6 GHz
  Band 1 Band 2 Band 3 Band 4
RF range/[GHz] 80-116 129-177 201-267 277-371
T$_{\rm rec}$/[K] LSB 40-55 30-50 40-60 30-50
T$_{\rm rec}$/[K] USB 40-55 40-80 50-70 30-50
G$_{\rm im}$/[dB] -10 -12 ... -10 -12 ... -8 -20
RF LSB/[GHz] 80-104 129-165 201-264 277-359
RF USB/[GHz] 104-116 164-177 264-267 289-371


next up previous contents index
Next: Correlators Up: Capabilities Previous: Spatial Resolution   Contents   Index
Gildas manager 2015-03-19