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RE: [linrad] RE: Linrad

Hi, Leif.

On Sat, 28 Jun 2003, Leif Asbrink wrote:

> Not when it arrives at the A/D converter, because then it has passed through
> our analog hardware, but when the pulse is a free wave and arrives at
> the antenna, then it has to be a "dirac pulse" as understood within the 
> bandwidth we are going to process. The analog filters will lengthen the pulse
> and distort the phase and amplitude functions. The calibration procedure
> will result in a digital filter that removes the distortion.
> The final consequence is that a dirac pulse in free space will become a
> symmetric pulse within Linrad.

OK. It bacame symmetrical after frequency and phase correction.

> In my experience it is not white noise. It is most probably another
> pulse. Therefore "Certanly all of this should be done in small time 
> window to avoid effect of another pulse. One should limit the time 
> interval in correlator by this window." leads to the use of three
> data points only.
> I have found that a simple parabolic fit to the three data
> points will give the same result as sliding the interpolated
> pulse shape along the three data points looking for maximum
> correlation. 

Though this procedure is different but mathematicaly equvivalent to
correlator maximization. If one use three data points time window of cose.
Also You precalculate as much as posible (pulse table). CPU will be
overloaded othervice. Nice done...

73 de RA9MB/Alex