Experimental Log: Roger Bland, November 26, 2001
Tests of Matched Filtering for RAFOS Sources )
( logbook | ifremer on RAFOS |Garfield at NPS )

Yesterday I found what seems to be an acceptable form for the replica to use with RAFOS signals from the Webb sources in the Eastern Pacific. I will carry out some tests to show that the correlation process works like I think that it does.

I have set up software to calculate a "replica" for a RAFOS signal and correlate it with the signal received on the PSM VLA. The signal is exactly 80 seconds long, and consists of a sine wave starting at frequency f1 and sweeping up by an amount W over the 80 seconds. [f1 = 259.375 Hz and W =1.54 Hz are probably about right.] This signal is calculated for the series of time values which correspond to the recorded time series from the VLA. The calculated signal is set to zero outside of the 80-second period starting at time t1, a parameter which can be varied from the console as the program runs. t1 is also the starting time for the frequency sweep.

The phase of the signal at time t1 is set to equal

2 p f1 t1 + f1,
where f1 is a parameter which can also be adjusted from the console. (In the later use of this replica the phase at time t1 will probably be set to zero.)

To compare this replica with observation I have proceeded as follows:

If the replica were exactly correct (right frequency, phase and starting time) and the data were without noise, the result would be just the square of the replica, thus a sine-squared function with 41500 peaks. Shifting a little off the correct value of t1 would the result would be