SineWave test, telescope test 05,06aug11
Links to sections:
05aug11:sine wave test
06aug11:data on telescope shows overflow wraparound
Links to plots:
wave test (.ps) (.pdf):
06aug11:tx sample voltages are displayed
for the 1st ipp of the file (.ps) (.pdf):
A test was
done with the rdev
spectrometer using a sinewave on 05aug11. On 06aug11 telescope data was
taken with the gregorian dome in dual beam mode.
- 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).
- Telescope setup:
- Cycling thru mracf, power, coded long pulse.
The Sine wave test:
The plots show the
test (.ps) (.pdf):
- 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.
- freq of sine wave correct for first ipp
- Not many birdies seen (although noise would probably be a
- Page 2:Measure phase differences
(Data -Tx) for 6000 ipps.
- Compute the phase of the sine wave for all data and tx samples:
- Top: phDataSmp[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
- 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.
- 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.
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.
- The measured phase difference (.6) equals the expected phase
difference except for 3 jumps.
- 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
- Page 3: Sampled and computed
sine wave for 1 ipp:
- The sampled data (black)
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
- 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
- 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
- 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.
- 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
The data from 06aug11 was taken from the gregorian
dome while the telescope was in dual beam mode.
The data came from:
- file /share/pdata/pdev/sasdr_final.20110806.b0a.00000.pdev
- first ipp of file (which was mracf)
The tx sample voltages are displayed for
the 1st ipp of the file (.ps) (.pdf):
- 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
- 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