Wapp Capabilities


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I. Single Pixel Spectral Line

  1. 195kHz to 50MHz Bandwidth
    • 1 polarization, 3-level autocorrelation: 16384 spectral channels
    • 2 polarizations, 3-level autocorrelation: 8192 spectral channels
    • 1 polarization, 9-level autocorrelation: 4096 spectral channels
    • 2 polarizations, 9-level autocorrelation: 2048 spectral channels
    • Full Stokes, 3-level autocorrelation: 8192 spectral channels
    • Full Stokes, 9-level autocorrelation: 2048 spectral channels
  2. 100MHz Bandwidth
    • 1 polarization, 3-level autocorrelation: 8192 spectral channels
    • 2 polarizations, 3-level autocorrelation: 4096 spectral channels
    • 1 polarization, 9-level autocorrelation: 2048 spectral channels
    • 2 polarizations, 9-level autocorrelation: 1024 spectral channels
    • Full Stokes, 3-level autocorrelation: 2048 spectral channels

II. ALFA Spectral Line

  1. 195kHz to 50MHz Bandwidth
    • 2 polarizations, 3-level autocorrelation: 8192 spectral channels
    • 2 polarizations, 9-level autocorrelation: 2048 spectral channels
    • Full Stokes, 3-level autocorrelation: 4096 spectral channels
    • Full Stokes, 9-level autocorrelation: 1024 spectral channels
  2. 100MHz Bandwidth
    • 2 polarizations, 3-level autocorrelation: 4096 spectral channels
    • Full Stokes, 3-level autocorrelation: 2048 spectral channels

Note The WAPPs always deliver their maximum number of spectral channels, this cannot be set to a lower number.

Note 9-level autocorrelation achieves 96% of the signal-to-noise of analog correlation; 3-level autocorrelation achieves 81%.

III. Pulsar Modes

  • 50MBytes/s max for correlator board
  • >50MBytes/s max for EDT/computer
  • 38MByte/s max data rate to disk

The best resolution for a 100MHz bandwidth, using 16 bits/lag, and summing the polarizations is given by the formulae:

     #lags = (i - 1)* 6.25,  where i = integration time in usecs
     Data rate to disk = 12MBytes/s;  Resolution = 100MHz/#lags
Integration time Max lags Resolution
100µs 616 162kHz
64µs 392 255kHz
32µs 192 520kHz

Direct Sampling

2 channels,continuous sampling

Bandwidth(MHz)Data Rate (Mb/s)Bit Packing
50 25 1
25 25 2
12.5 25 4
6.25 12.5 4
3.125 6.25 4
1.56 3.12 4
0.78 1.56 4
0.390 0.78 4
0.195 0.39 4