Medicina_Correlator - david-macmahon/wiki_convert_test GitHub Wiki
Summary
The Medicina correlator is a CASPER packetised correlator operating on 8 cylinders of the Northern Cross's NS arm.
It has 32 single polarisation inputs and processes 40MHz bandwidth (usable 16MHz) centered at sky frequency 408MHz at an IF of 40MHz, oversampled at 160MHz. As at 01 October 2008 it was using X_rev309c and F_rev303.
This page details installation and configuration procedures.
Array Details
Numbering convention
The following table details numbering convention and current interconnect.
Correlator internal - external mapping showing physical connections
phy DP SP PHY location relative to ref pos.
ADC IBOB BEE_fpga XAUI ANT ANT INPUT in wavelengths at 408MHz
===============================================================================================
bottom I 0 0 0 0x 0 1N-1-3 6.804708,-18.8875321,0
bottom Q 0 0 0 0y 1 1N-1-4 6.804708,-10.8875321,0
top I 0 0 0 1x 2 1N-1-1 6.804708,-34.8875321,0
top Q 0 0 0 1y 3 1N-1-2 6.804708,-26.8875321,0
------------------------------------------------------------------------------------------------
bottom I 1 1 0 2x 4 1N-2-3 20.414123,-18.8875321,0
bottom Q 1 1 0 2y 5 1N-2-4 20.414123,-10.8875321,0
top I 1 1 0 3x 6 1N-2-1 20.414123,-34.8875321,0
top Q 1 1 0 3y 7 1N-2-2 20.414123,-26.8875321,0
------------------------------------------------------------------------------------------------
bottom I 2 2 0 4x 8 1N-3-3 34.023538,-18.8875321,0
bottom Q 2 2 0 4y 9 1N-3-4 34.023538,-10.8875321,0
top I 2 2 0 5x 10 1N-3-1 34.023538,-34.8875321,0
top Q 2 2 0 5y 11 1N-3-2 34.023538,-26.8875321,0
------------------------------------------------------------------------------------------------
bottom I 3 3 0 6x 12 1N-4-3 47.632953,-18.8875321,0
bottom Q 3 3 0 6y 13 1N-4-4 47.632953,-10.8875321,0
top I 3 3 0 7x 14 1N-4-1 47.632953,-34.8875321,0
top Q 3 3 0 7y 15 1N-4-2 47.632953,-26.8875321,0
------------------------------------------------------------------------------------------------
bottom I 4 0 1 8x 16 1N-5-3 61.242368,-18.8875321,0
bottom Q 4 0 1 8y 17 1N-5-4 61.242368,-10.8875321,0
top I 4 0 1 9x 18 1N-5-1 61.242368,-34.8875321,0
top Q 4 0 1 9y 19 1N-5-2 61.242368,-26.8875321,0
-----------------------------------------------------------------------------------------------
bottom I 5 1 1 10x 20 1N-6-3 74.851783,-18.8875321,0
bottom Q 5 1 1 11y 21 1N-6-4 74.851783,-10.8875321,0
top I 5 1 1 12x 22 1N-6-1 74.851783,-34.8875321,0
top Q 5 1 1 13y 23 1N-6-2 74.851783,-26.8875321,0
-----------------------------------------------------------------------------------------------
bottom I 6 2 1 14x 24 1N-7-3 88.461198,-18.8875321,0
bottom Q 6 2 1 14y 25 1N-7-4 88.461198,-10.8875321,0
top I 6 2 1 15x 26 1N-7-1 88.461198,-34.8875321,0
top Q 6 2 1 15y 27 1N-7-2 88.461198,-26.8875321,0
------------------------------------------------------------------------------------------------
bottom I 7 3 1 16x 28 1N-8-3 102.070613,-18.8875321,0
bottom Q 7 3 1 16y 29 1N-8-4 102.070613,-10.8875321,0
top I 7 3 1 17x 30 1N-8-1 102.070613,-34.8875321,0
top Q 7 3 1 17y 31 1N-8-2 102.070613,-26.8875321,0
================================================================================================
On each IBOB, the bottom ADC corresponds to ADC0. The top ADC is ADC1.
Each ADC has two inputs, labelled I and Q on the PCB. 'I' is on top, 'Q' is on the bottom. I corresponds to 'X' or North-South polarisation and Q 'Y' or East-West polarisation on a dual-pol design.
All of Medicina's NS arm has east-west, or 'Y' polarisation.
The meeting of the EW and NS arms is at location = 44:31:24.88, 11:38:45.56. Height above sea level ±50m. This is the reference point for all antenna locations. It is in the center of the EW-arm, and in between two NS-arm cylinders.
Each cylinder in the N-S arm is located 10m apart (13.609415 wavelengths at 408MHz).
Cylinders are numbered in groups of 8. Group 1 (the only one in use by the correlator at the moment) has its southern most cylinder just north of the reference point.
Each cylinder in the group is numbered South to North starting at 1.
Each cylinder is equipped with four receivers located 8.0 wavelengths apart (at 408MHz) (±5m) E-W.
Recievers on the cylinders are numbered 1 through 4, with one being on the west and four being at the east.
Receivers are numbered AB-C-D, where A is the group B is the arm (in this case always 'N' for NS arm) C is the cylinder number within the group (1 through 8) D is the receiver on the cylinder (1 through 4)
Hardware
The hardware consists of 8 IBOBs, 16 2GSs/s ADCs and one BEE2.
Results
We were able to design, configure and install the system and obtain our first image of Cassiopeia within 10 days. The following pictures show the image formed from 1 hour of captured data.
Notice the strong RFI in this waterfall plot of baseline 1-2.
This plot shows the phase of baseline 1-2 after RFI has been excised.
This is the deconvolved image. AIPY's CLEAN algorithm was used.
Zooming-in on the cleaned image shows that most of the source was
correctly resolved to the center pixel. The images are mostly due to the
poor resolution (only four receivers in the E-W direction, with equal
spacing). Making use of the E-W arm of the Northern Cross will solve
this.
