On Tue, 24 Mar 2009 23:00:14 -0700 (PDT), JIMMIE
wrote:

On Mar 24, 9:45*pm, Richard Clark wrote:
On Tue, 24 Mar 2009 23:47:52 GMT, "Harold E. Johnson"

wrote:
Deep space communications proceeds many dB below the noise floor
enabled through technology that has become ubiquitous in cell phones -
Spread Spectrum. *I have developed pulsed measurement applications for
which any single pulse has a poor S+N/N, but through repetition
improves S+N/N response with the square root increase of samples
taken.

73's
Richard Clark, KB7QHC

And others call it autocorrelation?

Which?

73's
Richard Clark, KB7QHC

Radar people for one, also known as pulse-pair radar where data from
multiple returns are compared. The data can be from multiple hits on a
target using the same radar or the data can come from multiple radars.
MDS level improvement below the noise level can be achieved. Its also
used for transmitting data.One other specific use I am familiar with
involves transmition of radar data via radio. So the radar uses it as
well as the mode of transmission of the radar data from the radar to
the user.




Jimmie

My question of Which? was directed to Harold's broad brush painting
two different illustrations. Spread spectrum incorporates cross
correlation through slipping the gold code to find a flash. My design
performed a form of forced auto correlation (much like your radar
example, perhaps) but reduced noise as a function of that noise being
uncorrelated to the pulse.

Perhaps this is all saying the same thing at a very fundamental level.
However, I would guess this all hinges on the reduction of noise
following the square root of the ratio of the sample counts.
Conceptually, the distinction between auto or cross correlation is
really of minor consequence.

73's
Richard Clark, KB7QHC