Glitches in the atm digital receiver: test data 11aug05


The setup:

    The echotek digital receiver was used to take some test data on 11aug05.  The setup was:     The data taking program has two input buffers (100 ipps each). These get transferred to a set of 2 buffers (100 ipps each) which are then written out to disc. The data recording is continuous across files.

looking at the data:

    The data set had some records that were out of order.  This was evident when you looked at the transmitter samples. The power program and clp programs have different transmitter samples: To automatically differentiate between power and clp ipps, the rms was computed (using the I sample) for tx samples 1000 thru 1500. This region was close to zero for the power ipps (because of the blanking) while the clp ipps had the code here (so the rms would be large).

The first plot shows the spectra of the clp height data (.ps)   (.pdf).

The following plots show when the out of order records (glitches) occurred (.ps) (.pdf):     The glitches will only be seen near a program transition. If a power ipp is switched with a power ipp, then the rms's will be the same. It is only near the program transitions where the the difference is obvious. Since it is not locked to the transitions, the glitches are probably occurring at the start of each 100 second record.

    There are some points that don't line up. The clipping levels were picked using the first file. If the levels changed a little, or a different glitch (rfi) occurred, then the algorithm could mess up. Around ipp 180000 it looks like the cycling of the programs (power, clp) was stopped for awhile (no glitches) and then restarted (or maybe the receiver was switched to load for awhile).

processing:  x101/050811/,