1. Atacama Large Millimeter/submillimeter Array Expanded Very Large Array Robert C. Byrd Green Bank Telescope Very Long Baseline Array DBE Implementation for VLBA Keith Morris & Matt Luce CASPER2010 August 18 th, 2010

2. DBE Contributors Haystack: – Alan Hinton, Arthur Niell, Shep Doeleman, Mikael Taveniku, Christopher Beaudoin, Chester Ruszczyk, Russ McWhirter NRAO: – Doug Gerrard, Bob McGoldrick, Hichem Ben Frej, George Peck, Steve Durand, Jon Romney, Craig Walker, Mike Revnell, Walter Brisken, Keith Morris, Jim Jackson, Miguel Guerra, Matt Luce CASPER KAT

3. The Very Long Baseline Array 3

4. VLB A Current IF Processing 4 Four IFs – Eight sidebands – 2 sidebands (upper/lower) per IF – 16MHz per sideband – 128 Mbps peak data rate

5. VLBA Upgraded IF Processing 5 Single sideband Up to Four IFs – 512MHz per IF – 4x128MHz sub-bands per IF – 16 total down-converters per DBE – 4096Mbps peak data rate

6. DBE Hardware: Overview 6

7. DBE Framework/Infrastructure 7

8. Synthesizer/Clock Distribution Board Inputs – 5MHz reference (Maser) – GPS 1 PPS Outputs: – 1024MHz (3 copies) 1.5 o RMS phase noise – 1 PPS (4 copies) Buffers ALC control signals from ROACH

9. Automated Level Control (ALC) Gain: -11dB to +20dB in 1dB steps Optional 20dB fixed attenuator 2 channels

10. ALC-Bandpass variation

11. ALC Delay variation

12. Anti-aliasing filter amplitude

13. Anti-aliasing filter: band edges

14. Anti-aliasing filter: stopband

15. Anti-aliasing filter: phase

16. DBE Framework/Infrastructure 16 Blue boxes are Haystack specific and will be replaced in the DDC personality

17. DDC: Block Diagram 17

18. ALC: Raw sample capture Accepts de-multiplexed samples from both ADC channels Selectable IF0/IF1 capture Output sample stream: – Up to 32768 time continuous samples of the raw ADC data Two access methods: – File – Network socket 18

19. ALC: Raw sample capture examples 19

20. ALC: Power setting loop 20 Relative Power – V rms to dBm – Adjust ALC linearly in dB

21. GUI: Device Browser, Matrix Switch

22. GUI: Device Browser, DBE

23. GUI: Monitor archive query tool 23

24. GUI: Monitor archive data

25. Results 1: Autocorrelation on LA 25

26. Results II: 0 Baseline Cross-correlation 26

27. Questions? 27

28. ALC Adjustment Range Nominal Input power to the DBE: -33dBm. 28 ALC Control Value Sampler Input power level RMS CountsSampler Head Room 0-12.0dBm3220dB 8-20.0dBm2322.5dB 16-28.0dBm1626dB 26-37.0dBm9.530dB 31-42.0dBm3.340dB

29. DDC: Specifications As per the VLBA sensitivity upgrade project book, the filters in the DDC personality must conform to the following: – Quantity:Eight DDCs per 512MHz wide channel – Tunable range:Within the 512MHz wide channel – Minimum tuning step:1 Hz (center frequency specified). – Output truncation: Any number of bits between 1 and 8. – Decimated output rate: 128 kbits/s – 2048 Mbits/s. – Return to previous phase after switching to another frequency/bandwidth and back. 29