The enhanced Pico Veleta correlator

Marc Torres, Philippe Chavatte , Sept, 2002







A very attractive solution for re-using the 1992-generation Plateau de Bure 6-unit correlator has been proposed by Gabriel Paubert in October,2000.

The concept is described in GP's paper "Multibeam correlator", version October 5th, and has been named "VESPA" , standing for Versatile SPectrometer Array.

The main weakness of  this technological generation is that its frequency agility is limited to 500 MHz, but if offers a great improvement in terms of number of channels, compared with the previous correlator system (18432 instead of 4096).

The 6 PdB machines exactly host all the modules for the system. They have been progressively loaded with the upgraded modules, as soon as they became available. Some of the necessary modules were already part of the operating PV correlator, and have been  locally transformed without service interrupt, thanks to the spares.

The new system has replaced the  current one and has the following aspect :

Vespa during its assembly in Grenoble







Its IF coaxial distribution involves a lot of cables and is described below, for the current 9-beam receiver:

Connexion to the IF distibution system




 
 

4-Receiver auto-correlation operating modes

Bandwidth Sub-band  Time Multiplex Factor Lags number Real channels Channel spacing
24 x 160 MHz LSB + USB 4 24 x 128  24 x 128  1.250 MHz 
24 x 80 MHz LSB + USB 2 24 x 256  24 x 256  320 kHz 
24 x 40 MHz LSB + USB 1 24 x 512  24 x 512  80 kHz 
18 x 40 MHz LSB + USB 1 pass along 18 x 1024  18 x 1024  40 kHz 
18 x 20 MHz LSB or USB 1 pass along 18 x 1024  18 x 1024  20 kHz 
6 x 20 MHz LSB or USB 1 pass along 6 x 2048  6 x 2048  10 kHz 
6 x 20 MHz LSB or USB 1 pass along 6 x 3072  6 x 3072  6.6 kHz 
 6 x 10 MHz
 USB
 1 pass along
 6 x 3072
6 x 3072
3.3 kHz

 
 

4-Receiver cross-polarisation operating modes

Bandwidth Sub-band Time Multiplex Factor Lags number Complex channels Channel spacing
24 x 80 MHz USB 4 12 x 64  12 x 32  2.500 MHz 
12 x 40 MHz USB 2 12 x 128  12 x 64  625 kHz 
12 x 20 MHz USB 1 12 x 256  12 x 128  160 kHz 
12 x 20 MHz LSB or USB 1 pass along 12 x 512  12 x 256  80 kHz 
6 x 20 MHz LSB or USB 1 pass along 6 x 1024  6 x 512  40 kHz 

 
 

Multi-Beam auto-correlation operating modes

Bandwidth Sub-band  Time Multiplex Factor Lags number Real channels Channel spacing
36 x 160 MHz LSB + USB 4 36 x 128  36 x 128  1.250 MHz 
36 x 80 MHz LSB + USB 2 36 x 256  36 x 256  320 kHz 
36 x 40 MHz LSB + USB 1 36 x 512  36 x 512  80 kHz 
18 x 40 MHz LSB + USB 1 pass along 18 x 1024  18 x 1024  40 kHz 
18 x 20 MHz LSB or USB 1 pass along 18 x 1024  18 x 1024  20 kHz