Digital spectrometers for the nobeyama 45-m telescope

摘要

New digital spectrometers for the 25-BEam Array Receiver System (BEARS) of the Nobeyama 45-m telescope are described. A commercial digital oscilloscope is used as a digitizer. The digitizer samples analogue data with 2 bits (4 levels). Data of 512 MHz bandwidth are processed for four beams at the same time. The data-formatting unit demultiplexes 2 bits 8 data in parallel to 32 parallels and sends outputs to LSIs. General purpose LSIs for autocorrelation read the digital data with a clock rate of 32 MHz. Thiry-two LSIs of 32 lags connected in cascades calculate 1024-lag autocorrelation, and output a 10240-chammel power spectrum of 512 MHz bandwidth. The bandwidth of 32 MHz is achieved by picking up the data in a 1024-channel power spectrum of 512 MHz bandwidth. The bandwidth of 32 MHz is achieved by picking up the data in a rate of 1/16 in the front part of the autocorrelator module. The total performances have been demonstrated bylong-term integration o f noise signals from receivers and observations of the Galactic star-forming region W51 in CO line.