Документ взят из кэша поисковой машины. Адрес оригинального документа : http://www.naic.edu/~aoftm/specs.ps Дата изменения: Mon Mar 24 18:55:00 1997 Дата индексирования: Mon Oct 1 20:09:11 2012 Кодировка:

24 Mar '97
ARECIBO OBSERVATORY FOURIER TRANSFORM MACHINE
The AOFTM is a fast­dump spectrometer with programmable numbers of channels
and time resolution. It includes all hardware necessary to channelize two IF signals,
mix to baseband, digitize, and Fourier analyze, yielding power spectra into the RAM
of a Sparc station. It uses spectrometer boards built around the Austek A41102 FFT
chip. Microcontrollers on these boards provide direct control of the FFT chip as well
as configuring on­board RAM for integrating spectra. I/O with the Sparcstation
is through a fast parallel Sbus card. The Sparcstation configures the spectrometer
and commands calibration runs for on­the­fly normalization of spectra prior to 2­bit
packing. An optional external time tick can be used to initiate data acquisition.
Telescope monitor data and station time will be accessed through ethernet and a
direct serial line.
Specifications:
Total bandwidth: 10 MHz.
Frequency channels: N љ = 2 \Gamman 1024; n = 0; 1; 2; 3; 4.
Time resolution: \Deltat = m2 \Gamman 102:4 Їs; 1 џ m џ 2 n \Theta 16.
Prompt and delayed FFT computations (50% time overlap).
Bandpass normalization for each of 16 spectrometer boards.
Aggregate 40 Mbyte s \Gamma1 data rate from spectrometer boards.
Hardware summing of polarization and overlap channels.
2 bit sampling ) 2:5 Mbyte s \Gamma1 into Sbus parallel card.
Maximum DM at 430 MHz for no smearing = 50 pc cm \Gamma3 .
Hardware:
AGC at IF.
8 mixer/digitizer boards (2 ch/board) for 2 pol \Theta 4 subbands \Theta 2 overlap factor.
16 spectrum analyzer/accumulator (SPA) boards.
4 data­packer boards (DPB) for bandpass normalization, polarization and overlap
summing.
1 timing board for 2­bit packing, clock transfer, general traffic control.
EDT Sbus parallel card.
Sparc 5 workstation with 0.5 Gbyte internal disk.
External 8 Gbyte disk system for fast data dumps.
Exabyte 8500 & Exabyte Mammoth Tape Drives.
Software:
aoftm = Xwindows GUI & text menu control program for testing and low­level
data runs.
postproc = GUI for quick­look processing.
run aoftm = script to run all programs.
ao unpack = unpacking program ! standard output.
Recording Modes:
Direct to 8 Gbyte disk at up to fastest rate (=2.5 Mbytes s \Gamma1 ).
Direct to slow Exabyte for rates џ 312 kBytes s \Gamma1
Constraints on n; m for slow Exabyte:
m – 8
\Deltat – 102:4 Їs
2 n\Gamma3
=
819:2 Їs
2 n
; n = 0; 1; 2; 3; 4
Direct to Exabyte Mammoth Drive at up to fastest rate.