APEX facility backends

• XFFTS

  The RPG eXtended bandwidth Fast Fourier Transform Spectrometer (XFFTS) is optimized for a wide range of radio astronomical applications. The new digitizer and analyzer boards make use of the latest versions of GHz analogue- to-digital converters (ADC) and the most complex field programmable gate array (FPGA) chips commercially available today. These state-of-the-art chips made it possible to build a digital spectrometer with instantaneous bandwidth of 2.5 GHz and 32768 (32K) spectral channels. The APEX facility XFFTS consists of two units which have a fixed overlap region of 1.0 GHz, hence covering the entire IF bandwidth of SHeFI. The number of spectral channels is fixed to 32768.

• ABBA

  The ADC Backend for Bolometer Arrays uses commercial DAQ boards to digitize the 320 analog signals from the electronics of LABOCA over 16-bits. The AC bias frequency is provided by the data acquisition system as a submultiple of the sampling frequency (usually set to 1000 Hz) thus synchronising the bias to the data sampling. This electronics scheme is fundamental to the stability of the post-detection signals at low frequencies.

• FFTS

  The facility Fast Fourier Transform Spectrometer - now decommissioned - consists of two units with a bandwidth of 1 GHz each. Both units are configurable to provide up to 8192 spectral channels, thus providing a spectral resolution of up to 122 kHz. The two units can be connected to one receiver each, or the two units can be configured to produce a single backend with almost 2 GHz bandwidth. The placement of each unit is restricted by the IF range of the receiver.