07sep05 echotek test data show no glitches

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The setup:

• The transmitter was cycled between power profiles (10 seconds) and coded long pulse (10 seconds).
• The receiver was centered close to 430 Mhz.
• The ipp was set to 10 milliseconds.
• A single channel of  complex (16 bit I/Q)  data at 10 Mhz Bandwidth was recorded.
• Data was written in the .shs (simple header system) data format. Each file had:
• An ascii primary header
• multiple records containing an ascii data record header followed by 100 ipps of binary (short) data.
• Each recorded  ipp  included:
• 560 useconds of transmitter samples (5600*2 shorts)
• 4000 usecs of height data (40000*2 shorts)
• 5 usecs of noise data (50*2 shorts)
• 32 2gb files were recorded. Most files contained 117 records (11700 ipps). This was 117 seconds of data (since each record was 1 second). Occasionally there was a shortened file.

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looking at the data:

• Power: 52 usecs (520 samples) of transmitter sample followed by 200 useconds (2000 samples) of no data (since the blanking interval was set to 200 usecs for the clutter).
• Clp:  500 usecs (5000 samples) of transmitter sample followed by 60 usecs (600 samples) of blanking.

The 11aug05 data showed glitches (out of order records)  every 1 second. The 07sep05 data did not show any of these glitches. The differences in the two dates were:

• The 11aug05 data was centered at 434 Mhz. This caused the 430 Mhz code to rotate at 4 Mhz. The rapid rotation allowed the use of the rms to differentiate between code and no code. The 07sep05 data was centered at 430 Mhz so the code ended up at DC. To differentiate between code (clp)  and no code, the power in channels 1000-1500 was used.
• The burst counter for the echotek card was set to 50176 for 11aug05 and 46080 for 07sep05.
• The echotek card was configured for 7.5 Mhz bandwidth for 7sep05. On 11aug05 it only provided 5 Mhz bw.

 

 

The plots show  the ipps for the 32 files (.ps) (.pdf):

• Fig 1 top: This shows the power (black) and clp (red) tx samples for the I sample.  The gap  between 560 and 2600 in the power profile is from the IF blanking.  This starts at sample 5000 for the red (clp) data. The power was computed between sample 1000  and 1500. The clp had the code while the pwr program had no signal. The data comes from file.000 ipps .
• Fig 1 bottom: The spectral density was computed for 8192 samples of the codedlong pulse height data. 100 spectra were averaged. The plots shows that the echotek board was setup to provide 7.5 Mhz  of bandwidth. This differed from the 11aug05 data that only had 5 Mhz of bandwidth.
• Fig 2 top: This shows the pwr computed over samples 1000 to 1500 for each ipp in file.000 . There are 11700 ipps in the file. The file started with power (where the power was small). At ipp 1000  it switched to clp.  The dashed green lines showed where the program transitions occurred.  There were no single ipp glitches found. These were generated automatically using the algorithms described below.
• Fig 2 middle.. the glitches: To find the glitches, a 7 sample median filter was run across the 11700 ipps to create a median filtered array. Since the glitches were less than 4 samples, they where not included in the filtered array. The filtered array was then subtracted from the initial data. This removed the program and left the glitches. The result is plotted here. No glitches were found.
• Fig 2 bottom.. the program transitions: The pwr was median filtered (7 points long). The derivative of the filtered data was then taken (shift by 1 and subtract). The absolute of this is  plotted.  Anything larger than 5e5 a/d counts is considered a program transition.
• Fig3 top.. glitch to next transition: The distance from a glitch to the next program transition was computed for every glitch in the 36 files (445 glitches). This distance was then plotted versus the cumulative ipp (for the 36 files). You can see that the glitches are drifting in time relative to when the program transitions occur. This means that the problem is not related to the program transition itself. The drifting is 200 ipps. This is the length of the two buffers that are used for input.
• Fig 3 .. ipps between program transitions:. This plots the cumulative ipp for program transition modulo 1005.36 ipps. This shows that the programs were switching at ipps of 1005 or 1006. There were no single ipp glitches found.

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