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Plans for stochastic hardware injection. Eric Thrane, Mandy Pihlaja and Vuk Mandic. Overview. Motivation Injection flow chart Relationship to reviewed code Testing and validation. Summary of injection. spherical harmonic coefficients and spectrum specified

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plans for stochastic hardware injection

Plans for stochastic hardware injection

Eric Thrane, Mandy Pihlaja and Vuk Mandic

  • Motivation
  • Injection flow chart
  • Relationship to reviewed code
  • Testing and validation
summary of injection
Summary of injection
  • spherical harmonic coefficients and spectrum specified
  • User sets parameters of GPS, random seed, injection duration
  • Parent routine, SphMapToTimeSeries, calls simulateSkyMapTimeDomain, which returns time series [d1, d2] and overlapping time series [Ovrlp1, Ovrlp2] for {LHO,LLO}.
  • simulateSkyMapTimeDomain = reviewed stochastic code
summary cont
Summary cont.
  • Then…
    • FFT both time series
    • Apply frequency pendulum transfer function
    • Window time series using sin function
    • Combine time series and overlapping time series
  • Write combined h(t) to text file
  • sbaniso.c (based on standard injection code, sb.c) reads in text file and converts to binary
  • Sent to psinject
  • Sent to awg
injection flowchart
Injection flowchart


user-specified params: random seeds, seg dur, etc.

SpH map file: l, m, Plm

spectrum file: f, H(f)

gets time series

gets overlapping time series

FFT time series

Apply pendulum T(f)



Combine overlapping series

Write combined h(t) to files.





pg. 6

binary out





pg. 23

simulateskymaptimeseries m
  • Returns [d1(t),d2(t)] for LHO, LLO given user-specified P() and H(f).
  • Written by Stefan Balmer and Joe Romano
  • Reviewed during SpH review.
validation and testing fft
Validation and testing- fft
  • The next four slides show the process of applying FFT, the pendulum transfer function, and the iFFT to the time series.
  • Then there is a consistency check to make sure this process could be reversed
fft of time series
FFT of time series



Next slide is the frequency domain Pendulum transfer function is given by sb.c
  • tfH=ffrequency^2/constants
  • Constants = (2.05e-13)(0.764)(0.764)
fft multiplied by tfh
FFT multiplied by tfH

Time series


ifft back to time series
ifft back to time series

Time series


In order to check that the pendulum transfer function was applied correctly, the transformed time series had the following inverse process applied
    • FFT, inverse pendulum transfer function, iFFT
  • The plot of the ratio of the ‘inverted’ time series to the original time series is on the next slide.
  • Within very small rounding, the original time series is recovered (~1.0)
ratio of two time series
Ratio of two time series





  • Each time series segment is multiplied by the sine function in order for beginning and end to scale to zero.
overlapping and combination
Overlapping and combination
  • The overlapping time series lags the original time series by half of segment duration.
  • The second half of the current overlapping time series and the first half of the previous overlapping time series are concatenated to make the combined overlapping time series
  • The combined series is added to the original time series to form the final time series
final time series
Final time series



No modulation of the envelope
  • Rms value of the pre-windowed time series = 2.2348
  • Rms value of the combined time series = 2.2334
  • The close rms values of the two time series shows apparent agreement
checking code at lho and llo
Checking code at LHO and LLO
  • The code was run at LLO and LHO given the same random seed to check that the time series were the same
  • Data in Xcel sheet (next page)
  • Originally generates time series, applies transfer function, overlaps segments and sends to AWG
  • Modified to read in text files created by SphMapToTimeSeries.m, send to AWG, and delete file after use (sbaniso.c)
  • Already used for S5 (w/o Vuk’s hacks) and reviewed
  • Day long injection generated in one minute segments
  • In order to not create a 1TB injection file, SphMapToTimeSeries.m only generates three files at a time and waits for sbaniso.c to delete a file before continuing.