1024-MHz vs 512-MHz Bands for VLBI2010? East Coast VLBI Meeting Feb , 2011, Haystack Observatory Bill Petrachenko

Method for comparing 1024 and 512- MHz BW Systems Compare performance of a variety of and 512-MHz sequences. Figure of merit for comparison is minimum SNR/band for 5-σ broadband delay detection (lower is better) – see next slide. Sequence variations 4 use 512-MHz bands. 5 use 1024-MHz continuous bands. 2 use 1024-MHz bands with possible spaces. Some ensure full overlap with both S and X-band (green shading), which is beneficial for S/X compatibility modes. Some avoid the Direct Broadbast Satellite (DBS) bands (purple shading) to avoid possible RFI problems. Some use high frequencies to access lower source structure. Some assume 50% power at high frequency (darkened bands) to emulate feed/LNA roll-off.

VLBI2010 Frequency Sequences GHz 9.0 (221) – (286) – (284) – (290) – (157) – (168) – (179) – (183) – (190) – (145) – (179) – 1.49 SNR/band for 5-σ detection DBS X-band DBSS-band (Min flux (10-s, 16-Gbps)) Relative data volume 512-MHz bands 1024-MHz bands Split bands

Compatibility Concern: RDBE (2x512-MHz) vs DBBC2010 (1x1024-MHz) Six possible modes were considered 4 of 6 are compatible (See following slides) Some cases assume digital sideband flipping Easy to implement (flipping the sign of alternate samples).

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Nyquist filter Gsps Samplers

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Nyquist filter Gsps Samplers

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Nyquist filter Gsps Samplers

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Gsps Sum Samplers

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Gsps Sum Samplers

Sampling/BW Compatibility 2048-Gsps vs. 2x1024-Gsps Gsps Nyquist filters Gsps Sum Samplers

Extra slides

BWf1f2f3f4snr1snr2Smin ΔτΔτ ΔτΔτ