Back-end overview (both analog and digital) for VLBI2010 East Coast Geodetic VLBI Meeting Feb, 2011, Haystack Observatory Bill Petrachenko

Goals for the VLBI2010 back-end system Handle VLBI2010 mode of observation 4 bands each using both linear polarizations 1-GHz bandwidth per band 2-14 GHz input frequency range Achieve Optimum use of on-source time and record capability Burst mode Switch for routing to recorders Handle multiple inputs, e.g. More than one VLBI antenna on-site Holography antenna Reference antenna for antenna deformations and site ties

H-switch 4321 V-switch 4321 UV_512 UH_512 LV_512 LH_512 RDBE V H UDC (2-14 GHz) UV_512 UH_512 LV_512 LH_512 RDBE V H UDC (2-14 GHz) UV_512 UH_512 LV_512 LH_512 RDBE V H UDC (2-14 GHz) UV_512 UH_512 LV_512 LH_512 RDBE V H UDC (2-14 GHz) Burst Mode & Switch Recorder To external processing e.g. GPS Ant1Ant2HolographyReference Ant1Ant2HolographyReference VLBI2010 Back-end signal path block diagram Antenna inputs

Notes on back-end features (1 of 2) 4-to-1 switches on H- and V-inputs to allow automatic switching between, for example: Two antennas (Ant1 and ant2) of a 2-antenna site where the antennas are never scheduled to observe simultaneously. Reference antenna for determining antenna deformations and site ties Holography antenna for measuring antenna surface. Extra splitter outputs For external processing, e.g. GPS. Enhancements to UDC 2-14 GHz frequency range 2x anti-alias filtered 512-MHz 2x anti-alias filtered 512-MHz

Notes on back-end features (2 of 2) Enhancements to RDBE 2x 512-MHz 2x 512-MHz No gain-control? (already in UDC) Burst mode processor and switch (needed to avoid inefficient use of media (see attached plot) Max 32-Gbps input bandwidth, 8-Gbps from each RDBE Max 16(32?)-Gbps output bandwidth, 4(8?)-Gbps to each of up to 4 record systems Up to 30(?)-s record capacity at 32-Gbps input rate. Simultaneous read and write capability