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Digital Signal Processing Basics and AO Back-Ends

Digital Signal Processing Basics and AO Back-Ends

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Digital Signal Processing Basics and AO Back-Ends

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  1. Digital Signal Processing Basics and AO Back-Ends Luis A. Quintero Digital Section Head Electronics Department Arecibo Observatory SDSS7 - DSP and Backends Intro, 12 Jul 2013

  2. Introduction to Digital Signal Processing SDSS7 - DSP and Backends Intro, 12 Jul 2013

  3. ELECTRICAL VARIABLE Resistance, Capacitance, Voltage, etc System - World Quantity Voltage Signal Conditioning Transducer time time Continuous Signal Acquisition - Transducers SDSS7 - DSP and Backends Intro, 12 Jul 2013

  4. Discrete-time Signal Amplitude time Sampling Continuous-time Signal (real signal) Amplitude time SDSS7 - DSP and Backends Intro, 12 Jul 2013

  5. 1V -1V - 0.45 + 0.70 - 0.47 - 0.82 + 0.30 http://www.iusb.edu/ + 0.40 - 0.90 … Signal Storage in Computers time SDSS7 - DSP and Backends Intro, 12 Jul 2013

  6. 7 6 5 4 3 2 1 0 - 0.45 2 + 0.70 5 - 0.47 2 - 0.82 1 A/D + 0.30 … 4 + 0.40 4 - 0.90 6 … … Analog to Digital Converter – Quantization time SDSS7 - DSP and Backends Intro, 12 Jul 2013

  7. D/A … Digital-to-Analog Converter Analog to Digital Converter – Quantization time 2 5 2 1 4 4 6 http://www.iusb.edu/ … SDSS7 - DSP and Backends Intro, 12 Jul 2013

  8. Digital Signal Processing System Computer A/D D/A … … Analog-to-Digital Converter Digital-to-Analog Converter Computer (Digital System) - Micro Processor - DSP (MAC) - Logic Circuit - ASIC - PAL/CPLD - FPGA Data Storage Data Processing - Math Operations - Filters - Fourier Transform - Data Format SDSS7 - DSP and Backends Intro, 12 Jul 2013

  9. time 1 Second time Sampling Rate – Analog to Digital Fs = 9 samples/second = 9Hz Fs = 19 samples/second = 19Hz Better signal reconstruction More computer memory / BW and $$ SDSS7 - DSP and Backends Intro, 12 Jul 2013

  10. clk Analog to Digital Converter - Clock Input ANALOG DIGITAL A/D … Clock for digital circuit Stable – jitter SDSS7 - DSP and Backends Intro, 12 Jul 2013

  11. time Resolution Resolution: 3bits, 23 = 8 combinations 7 Values from 0 to 7 0 Resolution: 4bits, 24 = 16 combinations 15 Values from 0 to 15 time 0 Better signal quantization More computer memory and $$ SDSS7 - DSP and Backends Intro, 12 Jul 2013

  12. 7 time 0 Saturation • Resolution: 3bits, 23 = 8 combinations • Too much power to the ADC • Saturation caused by interference (RFI) SDSS7 - DSP and Backends Intro, 12 Jul 2013

  13. Sampling – FT, Nyquist and Aliasing SDSS7 - DSP and Backends Intro, 12 Jul 2013

  14. Sampling – FT, Nyquist and Aliasing Fs = 200Hz, Ts = 5ms, Fs/2 = 100Hz SDSS7 - DSP and Backends Intro, 12 Jul 2013

  15. Signal Processing – Adder 4bit adder 4 5 = 4 1bit adder SDSS7 - DSP and Backends Intro, 12 Jul 2013

  16. Signal Processing – Multiplier 4 8 4 • Multiplication by a Constant – Gain • Multiplication by -1, Sign change • Multiplication by a function – e.g. sin/cos - up/down conv. • Things to consider • Bit growing • Precision – Approximation Errors SDSS7 - DSP and Backends Intro, 12 Jul 2013

  17. DATA ADDR n Phase Increment Mem - LUT Signal Processing – Functions, e.g. sin/cos x[n] x[n] * sin[n] sin[n] DDS SDSS7 - DSP and Backends Intro, 12 Jul 2013

  18. clk latency Signal Processing – Synchronization SDSS7 - DSP and Backends Intro, 12 Jul 2013

  19. Filtering – e.g. Finite Impulse Response (FIR) SDSS7 - DSP and Backends Intro, 12 Jul 2013

  20. Auto Correlation SDSS7 - DSP and Backends Intro, 12 Jul 2013

  21. Discrete Fourier Transform - DFT X[k] =FNx[n] FFT – Fast Fourier Transform, optimized DFT (butterflies) SDSS7 - DSP and Backends Intro, 12 Jul 2013

  22. Examples with Signals • Fourier Transform • Saturation • Averaging • Clock Jitter SDSS7 - DSP and Backends Intro, 12 Jul 2013

  23. Fourier Transform, one tone SDSS7 - DSP and Backends Intro, 12 Jul 2013

  24. Fourier Transform, two tones SDSS7 - DSP and Backends Intro, 12 Jul 2013

  25. Fourier Transform, noise effect SDSS7 - DSP and Backends Intro, 12 Jul 2013

  26. Fourier Transform, averaging SDSS7 - DSP and Backends Intro, 12 Jul 2013

  27. Fourier Transform, longer transf. SDSS7 - DSP and Backends Intro, 12 Jul 2013

  28. Fourier Transform, Saturation SDSS7 - DSP and Backends Intro, 12 Jul 2013

  29. Fourier Transform, Clock Jitter 0% Jitter 40% Jitter SDSS7 - DSP and Backends Intro, 12 Jul 2013

  30. Applications in Radio Astronomy SDSS7 - DSP and Backends Intro, 12 Jul 2013

  31. Gregorian Dome Receivers Ganesan, R. “Telescope Electronics”, May 2006 SDSS7 - DSP and Backends Intro, 12 Jul 2013

  32. Radio Frequency Signal Path SDSS7 - DSP and Backends Intro, 12 Jul 2013

  33. Signal Transport – Intermediate Freq. SDSS7 - DSP and Backends Intro, 12 Jul 2013

  34. Final Stage – Data Acquisition Data Sampling and Storage SDSS7 - DSP and Backends Intro, 12 Jul 2013

  35. Bandpass Signals in IF SDSS7 - DSP and Backends Intro, 12 Jul 2013

  36. Sampling - Nyquist Zones & Analog BW SDSS7 - DSP and Backends Intro, 12 Jul 2013

  37. Wideband Arecibo Pulsar Processor (WAPP) • 4 WAPPs • 1 WAPP = 2 IF Channels • 2 Correlators • 1 Multiplexer • 50/100 MHz BW • auto / crosscorrelations • Step attenuators • Technical issues: • Difficult to troubleshoot • Obsolete parts SDSS7 - DSP and Backends Intro, 12 Jul 2013

  38. Wideband Arecibo Pulsar Processor (WAPP) SDSS7 - DSP and Backends Intro, 12 Jul 2013

  39. WAPP Correlators (~1995) High Performance CMOS Correlator Chip (ASIC) • 16 Chips per board • Autocorrelation / Crosscorrelation • 1024 Lags / chip • 100MSPS each • “Low Power” • TTL compatible http://www.naic.edu/~astro/general_info/correlator/cmos.html SDSS7 - DSP and Backends Intro, 12 Jul 2013

  40. Complex Sampling SDSS7 - DSP and Backends Intro, 12 Jul 2013

  41. Arecibo L-band Feed Array • 7 Receivers • Dual Polarization • 14 analog signals • 1225 – 1525MHz • 300MHz BW • Designed by Germán Cortés Medellín (Cornell) Ganesan, R. “Telescope Electronics”, May 2006 SDSS7 - DSP and Backends Intro, 12 Jul 2013

  42. Complex Sampling Example: ALFA 1225 1525 SDSS7 - DSP and Backends Intro, 12 Jul 2013

  43. Mock Spectrometer / PDEV (~2007) • Designed and developed by Jeff Mock • 8 x AD9430, 12bits ADCs • 2 x Xilinx Virtex II Pro FPGA • 2 QDR Mem, 2M x 36 • 1x PowerPC Processor • Flash & SRAM mems • 2 x GbE, 2 x RS232 • 5 x SMA (clk, PPS, etc) • LCD 128x64 pixels Digitizers Digital Board SDSS7 - DSP and Backends Intro, 12 Jul 2013

  44. PDEV – Architecture QDR 2Mx36 Flash / SRAM PCIe x8 MGT ADC GX 2VP70 ADC ADC ADC 2 x GbE PPC 440GX 2 x RS232 ADC ADC GX 2VP70 ADC ADC 4 x SMA PCIe x8 MGT QDR 2Mx36 SDSS7 - DSP and Backends Intro, 12 Jul 2013

  45. PDEV – Mock Spectrometer TEST SIGNAL CW, Noise, CW + Noise 12 ADC0 12 ADC0 SWITCH PROC. INT. PACKETIZE STOKES ACCUMULATOR GAIN/OFFSET PFB/FFT 16-8k DDC (DDS, LPF) 12 ADC0 12 ADC0 CONFIGURATION REGISTERS SDSS7 - DSP and Backends Intro, 12 Jul 2013

  46. EALFA / PALFA Backend 14 PDEVs* 7 for 7 ALFA pixels (primary) 7 for 7 ALFA pixels (commensal) 14 File servers (4TB) We own in total 24 PDEVs DDC (DDS, Mixer, DLPF) PFB (up to 8192 channels) Stokes parameters Accumulation, Packing * http://www.naic.edu/~phil/talks/vc09/tel_Perf_datatking_09.ppt SDSS7 - DSP and Backends Intro, 12 Jul 2013

  47. GALFA Spectrometer / GALSPECT (~2004) • Backend for the • Arecibo L-band Feed Array (ALFA) multibeam receiver • 7 beams, dual polarization • Outputs*: • Narrowband: 8192channels, • 7MHz BW • Wideband: 512 channels, • 100MHz BW SDSS7 - DSP and Backends Intro, 12 Jul 2013

  48. PR Ultimate Pulsar Processing Instrument ( PUPPI) • 100/200/400/800MHz BW • Polyphase Filter Bank • Dual Pol. 8 bit ADC • Full Stokes • 200MB per second recording (10GbE) • 0-15.5dB Level Control • PSRFITS data format • 1xBee2 + 2xiBOB SDSS7 - DSP and Backends Intro, 12 Jul 2013

  49. Recording Systems – Mark IV / 5A / 5C / RDBE • Mark IV + Mark 5A: 1Gbps (125MB every second) • RDBE + Mark5C: 4Gbps (500MB every second) • eVLBI, AO-UPR-Centenial link: 155Mbps all time512Mbps 24h-6h SDSS7 - DSP and Backends Intro, 12 Jul 2013

  50. Roach Radar Backend – RRB • Complex Baseband - Digital Down Converter (DDC) • 50MHz bandwidth max. • 2 x IF channels (polA/polB) • Bit selection, 8/4bits • 1.6Gbps max. data rate • Doppler correction • Programmable digital filter • Hardware (three systems):ROACH – Signal Proc.katADC – 2x1.5Gsps@8bitRAID Server, dual 10GbE • Fixed parameters: Summer 2012 SDSS7 - DSP and Backends Intro, 12 Jul 2013