Digital Signal Processing

yakzephyrAI and Robotics

Nov 24, 2013 (3 years and 11 months ago)

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Atacama Large Millimeter/
submillimeter

Array

Expanded Very Large Array

Robert C. Byrd Green Bank Telescope

Very Long Baseline Array

Digital Signal Processing

A Green Bank Perspective

John Ford

Contributions from Scott Ransom, Paul Demorest and
Jason Ray

Outline


Digital Signal Processing Trends


Available Computing Power


Architectures


Recent Developments at Green Bank


The Green Bank Ultimate Pulsar Processing Instrument (GUPPI)


Future Developments


Continuous GUPPI Upgrades


New GBT Spectrometer


New
Backends

for the 20 Meter
SkyNet

Project


Phased Array Feed
beamformers

2

DSP Trends


Computing Power

3

DSP Trends
-

Architecture


Possible Architectures


Multi
-
core conventional CPUs


Graphical Processing Units (GPU)


Reconfigurable Computing Elements (FPGA based Processors)

4

Heterogeneous Computing


A System consisting of two or more disparate types of computing
elements


Typically a mixture of the following


Traditional CPUs


Reconfigurable computing elements (FPGAs)


Graphical Processing Units


Use


Reconfigurable computing elements for the fastest streaming fixed
-
point signal processing and data distribution


GPUs for fast floating
-
point and memory intensive operations


General Purpose CPUs for managing the systems, handling data, and
for non
-
parallelizable parts of the computations


5

Pulsar
Backends


Search mode
backends


Fast
-
dump spectrometer


Time resolution of 50 to 100 microseconds


Frequency resolution of 25 KHs to 1 MHz


Bandwidth more important than data quality


Timing
backends


Known pulsar period allows folding data


Coherent De
-
dispersion required


Very high time resolution, ~ 1 microsecond


Data quality is important

6

GUPPI Specifications


Search Mode


Dual polarization, 8 bit real sampling, 800 MHz bandwidth inputs


Configurable signal processing


64 to 4096 spectral channels


100, 200, 400 and 800 MHz bandwidth


Configurable output rates and dump time


4, 8, or 16 bit outputs at ~50 microsecond dump time


Front end hardware capable of supporting Coherent De
-
dispersion
modes


Timing Mode


800 MHz Coherent De
-
dispersion


1 to 4 MHz channel widths, 8 bit sampling

7

GUPPI Hardware Configuration

8

GUPPI Block Diagram

9

GUPPI Signal Processing with CASPER

10

Complete

GUPPI

11

Interstellar Dispersion

12

GUPPI Coherent De
-
dispersion Mode

13

Profile Comparison

14

Profile Comparison

15

Future Developments


Continuous GUPPI enhancements


More bandwidth


New algorithms


Array receiver/ multi
-
beam support


Multiple IF inputs


Huge data handling requirements


Huge computational load


New GBT Spectrometer


New
Backends

for Radio
SkyNet


Wide
-
band Phased Array Feed
Beamformers


Front
-
end signal processing

16

Development Systems

17

43m GUPPI with RFI package

18