Here we report the feasibility study of the enhanced correlator proposed by Japan for 3-way ALMA. First we briefly review the scientific significance of the enhanced correlator, which does NOT depend on the correlator architecture. Then we describe the proposal of a high-performance FX correlator system for an enhanced correlator of 3-way ALMA. This FX correlator system always realizes both super-high spectral-resolution ( < 0.1km/s at 40GHz ) and wideband ( > 700km/s at 850GHz ) observations simultaneously up to 850GHz for each 2GHz baseband of the ALMA IF system. This FX system consists of 1024 x 1024 - FFT parts, 4-bit cross-correlation parts, and control parts. Re-quantization and flexible frequency-channel smoothing is newly installed. Re-quantization reduces the lines of connection between F and X parts compared with the previous FX system. Flexible frequency-channel smoothing makes the output frequency channels from 524288(=512 x 1024) to 8192 per baseband and eliminates the fear that the large amount of frequency channels might increase the costs of post-detection computing and archiving. Realization of this correlator system will allow us to make breakthrough in both sub-millimeter line and continuum observations with 3-way ALMA. We present the detailed specifications, block diagrams, estimated hardware size and power consumption of the high-performance FX correlator system. Preliminary plan for its implementation to the 3-way ALMA is also commented.
View a pdf version of ALMA Memo #350.
Last modified: March 05, 2001
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