Backends for EMIR and HERA

Backend

Type

Channel Width

Bandwidth

Receiver (width mode)

Status

FTS

FFTS

195 kHz

8x4 GHz

EMIR, HERA

haken.gif

FTS

FFTS

50 kHz

EMIR, HERA (narrow)

haken.gif

WILMA

Autocorrelator

2 MHz

16 or 18 x 930 MHz

EMIR, HERA (wide)

haken.gif

VESPA

Autocorrelator

3.3 kHz-1.25 MHz

10-512 MHz

EMIR

haken.gif

XPOL

VESPA

40kHz-2.5MHz

20-640MHz

EMIR

haken.gif

nbc / continuum

continuum

1 GHz

haken.gif

bbc

continuum

8 GHz

EMIR

haken.gif

4 MHz

Filterbanks

4 MHz

8 or 9 x 1GHz

EMIR, either HERA1 or HERA2 (wide)

kreuz.gif

See here, for the present status of the backends. For more information on the capabilities of EMIR, see here. In general, several backends can be attached to one receiver. Exceptions are listed below. The pako manual describes in detail how to configure the backends.

  1. Fast Fourier Transform Spectrometer (FTS): In July 2011, we installed 24 FTS units to cover 32GHz of bandwidth. The resolution is 200 or 50kHz. They are available to all observers since 2-Aug-2011. See the short commissioning report and the document of Gilles Butin on the Spectrum Slicers for FFT Spectrometers. Also see the backend status page. These FTS have been designed by Bernd Klein at the MPIfR/Uni Bonn and manufactured by Radiometer Physics. See Klein et al. 2012, A&A, papers of 2009, 2008, and a presentation of 2011.
    The exact frequency ranges are (GP, 21-Jul-2011):

    • - EMIR wide mode (~200kHz resolution):
        20737 channels (~4050.195MHz) centered at 5975.0MHz.
        First channel at 3950.0MHz, last channel at 8000.0MHz.
        There is an overlap of 320MHz between the inner and outer parts.
        The first 50MHz are "bonus" bandwidth, which will be
        very useful if the outer folding frequency is changed to 15.95GHz.
      
      - EMIR narrow mode (~50kHz resolution):
        37275 channels (~1820.068MHz) centered at 6200.0MHz
        First channel at ~5289.990MHz, last channel at ~7110.010MHz.
      
      - Hera wide mode (~200kHz resolution):
        5377 channels (~1050.195MHz) centered at 609.375MHz.
        First channel at 84.375MHz, last channel at 1134.375MHz.
      
      - Hera narrow mode (~50kHz resolution):
        12814 channels (~625.684MHz) centered at ~397.192MHz.
        First channel at 84.375MHz, last channel at ~710.010MHz.
      
      As long as we keep the current folding frequency for outer bands, 
      outer band are always at 15680-inner in MHz, so in the case of EMIR 
      narrow mode, 15680-6200 = 9480. (GP, 19-Sep-2011)
      
      For Wilma replace 5975 by 5985. (GP, 13-Jan-2012)


  1. WILMA: The Wideband Line Multiple Autocorrelator for EMIR and HERA

  2. VESPA: The Versatile SPectrometer Array. Up to 18000 channels. In connection with HERA (9 pixels) the following combinations of resolution (kHz) and bandwidth (MHz) are possible: (20/40), (40,80), (80, 160), (320,320), (1250, 640); VESPA User Guide (2002), Summary in IRAM Newsletter No. 54 (Dec 2002), local contact: G. Paubert

  3. XPOL: Line and continuum polarimetry is possible at the 30m using a new type of IF polarimeter designated XPOL. The central feature of XPOL is the correlator VESPA where the IF signals from two orthogonally polarized receivers are cross correlated to determine the four Stokes parameters. Further information is provided here.

  4. The old continuum backend, now called narrow band continuum backend nbc with 1GHz width, is still available for HERA, and also for EMIR.

  5. The broad band continuum backend bbc with 8GHz width, fully exploiting the bandwidths of EMIR, is available since 2-Aug-2011. bbc cannot be connected to HERA.

Decommissioned backends:

  1. MAMBO2 has been decommissioned mid 2011. ABBA1 and ABBA2 (Adc Bolometer Backend) were the bolometer backends for the MAMBO 1mm camera, i.e. dedicated PCs connected to the bolometers.

  2. The 1MHz filterbank has been decommissioned in 4/2008: max. 4 parts; series, parallel, or mixed mode possible; using the 1MHz filterbank with 1GHz bandwidth excludes the use of VESPA with the same receiver. The filterbank can be shifted in multiples of 32MHz from the center frequency of the connected receiver.

  3. 4MHz Filterbank: Desactivated on 21-May-2014. Max. 9 parts; use of the 4MHz filterbank excludes the use of VESPA on the same receiver. Frequency switching not available. While the channel spacing is 4MHz, the 3dB width is 5.4MHz and the noise equivalent width is 6.5 MHz

Distribution of intermediate frequencies (IFs) to the backends

Current IF distribution

FE_to_BE_v3.jpg
IF distribution in June 2014

Historic IF distribution <June 2011>

NEWBE_dec10v2.jpg
IF distribution 16-Dec-2010

Backends (last edited 2023-04-02 21:41:14 by damour)