Intro:

The setup:

• Rdev setup :
  
• 160 MHz clock, decimate by 5: 32 MHz Bw, 16 bits output, data  rate 32 MHz i,q.
  
•  txSamples: 20000
• HghtDelay: 30000 samples
  
• hghtSamples: 65000 samples starting (30000)/32e6=.9375 milliseconds =140.6 Km range.
• 32 MHz readout upshift was set to 11.
  
• Rdev setup for sine wave.
• 10 millisecond ipp fed into rdev from sps.
  
• sine wave= 30MHz+ 11160 hz, amp=14dbm.
• took 4 files of data (about 60 seconds/file).
  
• SineWave: /share/pdata/pdev/tests_aug5/sine_32M/sasdr.20110805.b0a.01100.pdev  thru .01103.pdev
  
• Telescope setup:
• Cycling thru mracf, power, coded long pulse.
  

The Sine wave test:

• Page 1:Spectra of 1st ipp
• Top: spectra of 20000 tx samples.
• 2nd: spectra of 65000 data samples.
• 3rd: blowup of tx spectra showing sine wave
  
• 4th: blowup of data spectra showing sine wave.
• Conclusions:
• freq of sine wave correct for first ipp
• Not many birdies seen (although noise would probably be a better test)
  
• Page 2:Measure phase differences (Data[0] -Tx[0]) for 6000 ipps.
• Compute the phase of the sine wave for all data and tx samples:
•  phDataSmp[nsmp,nipps],phTxSmp[nsmp,nipps].
  
• Top: phDataSmp[0,ipp] - phTxSmp[0,ipp]. 
  
• For each ipp measure phase difference (modulo 1 cycle) between the first tx sample and the first data sample.
• The expected phase difference is:
  
• Time DataSmp[0,ipp]-TxSmp[0,ipp]=(30000)/32e6= .9375 ms
• Period SineWave=1./11160=89.6057 usecs
• Excess phase= .9375/.0896057 mod 1. = .4625 cycles.
• Measured Phase dif=.4682 cycles and it is unchanging for each ipp of the file.
  
• phase Error=.512 useconds.
• Conclusions:
• There are no jumps txSample to data sample within an ipp for the entire file.
• The measured phase (tx to data)  is off by about .5 usecs from the expected time difference.
  
• 2nd:phTxSmp[0,ipp+1]-phTxSmp[0,ipp]: The change in tx sample 0 from 1 ipp to the next.
  
• The measured phase difference .26equals the expected phase difference except for 3 jumps.
• 3rd:phDataSmp[0,ipp+1]-phDataSmp[0,ipp]:
  
• The measured phase difference (.6) equals the expected phase difference except for 3 jumps.
• Conclusions:
• The tx to data(hght) phase is constant. It is off by .51 usecs from the expected value
• during 60 seconds there are 3 jumps  ippN to ippN+1
• The jumps occur in the tx samples and the data samples.
• This probably means that the ipp trigger to start the ipp was off.
  
• Page 3: Sampled and computed sine wave for 1 ipp:
• The sampled data (black) was plotted for 1100 usecs of the 2rd ipp. The time gap between the tx and data samples was included.
• A 11160 hz sine wave was generated (red):
• The expected frequency (11160hz) was used.
• The amplitude and phase were taken from a fit to the tx samples.
  
• Top: The measured (black) and computed (red) sine wave.
• The green vertical bar is the end of the tx window. the blue vertical bar is the start of the data window.
• 2nd: Blowup start of Tx window.
• The computed and measured sine wave are in agreement.
• 3rd: Blowup end of Tx window. The measured and computed sine waves are still in phase.
• 4th: The start of the Data window
• The sampled data (Black) is .6 usecs behind the txsinewave fit (about 19 samples) (same as the .51 usec delay measured on previous page).
• Conclusion:
• The tx and data samples are taken with different digitizers. This discrepancy is probably a gain variation, dcoffset in the two a/d's
• Page 4: Sample sinewave - fit sine wave for 2nd ipp.
• Data - fit was plotted for the sine wave in the 2nd ipp
• 0-600 Usecs:transmitter samples. These were used for the fit
• 600-900 usecs: no sampled data
• 900-100 usecs sampled data.

Sinewave Summary:

• The frequency of the sine wave is correct.
  
• Within 1 ipp, tx to data window sampling is stable for 60 seconds   . it is off by .5 usecs
• This may be because the noise, datawindows use different digitizers which may have different gains.
• There were 3 jumps in the timing ippN to ippN+1.
  
• The jumps were the same for the tx and the data windows.
• This may be a triggering problem with the  ipp pulse.
  

06aug11: telescope data shows overflow wraparound

• file /share/pdata/pdev/sasdr_final.20110806.b0a.00000.pdev
• first ipp of file (which was mracf)

• Top: tx sample voltages vs time. black is real, red is imaginary.
• middle: blowup of real samples. Green lines are max,min values.
• bottom: blowup of imaginary samples

summary:

• The numbers are wrapping around rather than clipping when they reach the maximum or minimum allowed values (-32768,+32767).
• the readout upshift of 11 is too much.
• The rdev should clip the output values rather then allow them to wrap around.
  

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