CASPER Development for GAVRT at Caltech

1. CASPER Development for GAVRT at Caltech Glenn Jones Aug. 03, 2008 2008 CASPER Workshop

2. Acknowledgements • Xilinx – Generous FPGA and software donations • Sandy Weinreb & Hamdi Mani – Feed measurement data

3. Useful stuff first!The Simulink scope is terrible!

4. gtkWave from Simulink for CASPER

5. gtkWave from Simulink for CASPER

6. Sick of ‘od -x’ for interpreting snapshot data?

7. gtkWave Snap – View SnapBRAM data

8. gtkWave Snap gtkgen(wave) $ gtkwave temp.vcd

9. Vector accumulator

10. Vector Accumulator

11. Utility blocks

13. 34 m telescope in southern California to be used by K-12 students to take data for astronomers. Currently being equipped with a novel ultra-wide-band radiometer designed at Caltech. Goldstone Apple Valley Radio Telescope

14. 0.5-2 GHz Uncooled feed LNAs cooled to 50K 4-14 GHz Feed and LNAs cooled to 15 K Wide band quad-ridge feeds

15. Receiver Noise Temperature

16. Crossover performance

17. 4 dual polarization pairs of receivers Input from 0.5 to 18 GHz Select bandwidth from 100 MHz / 500 MHz / 1 GHz / 2 GHz Downconvert to baseband. Front end box

18. 1 GHz LPF 1 GHz LPF 2 GHz BPF @ 22 GHz Basic Receiver Architecture 2-14 GHz Feed I I LNA LNA Q 0.5-4 GHz Feed 22 GHz Fixed LO 22-40 GHz Tunable LO The system consists of eight such receivers, arranged as four dual-polarization pairs.

19. Receiver modes • The I and Q outputs can optionally be combined in a hybrid to form upper and lower sidebands. Additional filter options are also available. • Currently only 8 of the 16 possible outputs are routed to the digital back-end. This will be upgraded in the future.

20. The digital backend • 8x ADCs, 8x iBOBs • 16x XAUI links to BEE2 • 2x 10 GbE links to Procurve switch • ~20x 1 GbE to small cluster

21. Basic signal processing infrastructure

22. Thesis goals • Build a unique instrument designed to take advantage of the wide bandwidth provided by the GAVRT telescope to measure the following: • Detailed spectral characteristics of giant pulses from the Crab and other pulsars • Extensive statistics of giant pulses vs. frequency • Nanostructure in giant pulses • Dynamic spectra of pulsars with unprecedented bandwidth • RFI performance in light of modern mitigation techniques • IQ imbalance correction

23. Thesis Goal: Detailed spectra of giant pulses What we want to look at:Crab Giant pulses vs. Frequency “Earlier, we had noted the potential spectral similarity between giant pulses from pulsars and that of the Sparker. It would be useful to determine the road-band spectrum of giant pulses, say from 1-m to 10-cm wavelength. In short, we are advocating the study of giant pulses from pulsars as convenient plasma laboratories that may further our understanding of the fleeting Sparkers.” - Sri Kulkarni “Giant Sparks at Cosmological Distances?” From: Cordes et al. 2004 ApJ 612 375

24. Thesis Goal: Nanostructure in giant pulses What we want to look at:Crab Giant pulses vs. Frequency From: Cordes et al. 2004 ApJ 612 375 Hankins & Eilek, ApJ 670:693-701, Nov 2007

25. What we want to look at:Giant pulses vs. Frequency Hankins & Eilek, “Radio Emission Signatures in the Crab Pulsar.” ApJ 670:693-701, Nov 2007

26. Current limitations to giant pulse observations • Multiple frequency observations have generally required simultaneous observation with many telescopes  little data available • Ultra-high time resolution has been limited by: • Feed/receiver bandwidth • Dispersed pulse is longer than memory buffer • Lack of dedispersed trigger • More susceptible to RFI • SNR of dispersed pulse too low to trigger on

27. GAVRT Transient Capture Mode Raw data input rate: 16 Gbyte/sMax data output rate: 2 Gbyte/s RAM buffers are sufficient to store 1 second of raw voltages from 2 chan * 2 pol * 4 Gsps

28. Thesis Goal: RFI Performance Frequency domain IQ correction specialized for spectroscopy f0 FFT or PFB Filterbank (Real) f1 i(t) Corrected Spectrum fn FFT or PFB Filterbank (Real) Cn= j if i(t) and q(t) were in perfect quadrature Looks like it requires n complex multiplies and adds, but FFTs are pipelined, so only requires 4-8 plus RAM for cn much more efficient than time domain for same level of image rejection c0 c1 q(t) cn

29. Front Back

30. Incoherent Dedispersion

31. Do you see the pulsar? No Dedispersion

32. BEE2 DRAM Circular Buffer • 2^k sub-buffers per DIMM, k = 0…8 •  500ms to ~2ms @ 2 Gsps DRAM0 - 1 GB XAUI0 10GbE XAUI1 Up to 20 Gbps 16 Gbps for 2Gsps@8bits DRAM1 – 1 GB

33. Goals • Spectroscopy/Polarimetry • Currently (iBOB based): • 4096 ch spectrometer single pol • Dual 512 and Single 1024 ch fast dump for pulsar • Goal: spectrometer with “zoom” mode • Need to add enable to PFB-FIR block and VACC block • Hope to do RFI excision

34. iADCStability TestsPreliminary!

35. -6dBm Anritsu, 3dB modulation

36. +0dBm Anritsu, 3dB modulation +0dBm noise, 20dB atten before ADC

37. -6dBm Anritsu, 3dB modulation

38. 9dB modulation, 0dBm Anritsu

39. 6dB modulation, 0dBm, +/-5% scale

40. 6dB modulation -10dBm (10dB below total noise)

41. No Input

42. -6dBm Anritsu, 3dB modulation no noise

43. Goals • Pulsar Observations • Transient (giant pulse) capture • Incoherent trigger