[EMAIL PROTECTED] wrote: > > In a message dated 3/30/2007 23:47:12 Pacific Daylight Time, > [EMAIL PROTECTED] writes: > > Thermal noise and other noise in each channel are statistically > independent and their product averages to zero. > The actual residual decreases as the number of spectra averaged increases. > > > > Hi Bruce, > > hmmm. Not sure I understand. I thought that if you average Gaussian noise > sources the noise would only be reduced by a factor of root(n), n being the > number of channels; and not totally cancel out? Is the difference caused by > creating a product of the two channels rather than a summation? > > bye, > Said > > > > ************************************** See what's free at http://www.aol.com. > _______________________________________________ > time-nuts mailing list > [email protected] > https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > > Said
Multiplying the 2 signals is essential as the non correlated components of the 2 signals will then average to zero (for infinite measurement time) whilst the correlated components of the 2 signals will not. A cross spectral analysis is somewhat analogous to using an array of single frequency correlators. The residual noise decreases as the integration time increases. When multiple power spectra are averaged the noise floor will decrease as 1/n where n is the number spectra averaged. Bruce _______________________________________________ time-nuts mailing list [email protected] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
