Now You See It, Now You Don´t

The signal enhancement properties of a single-loop delayline integrator (DLI) are derived for operation in the presence of correlated noise. The signal is assumed periodic with a period equal to the delay of the DLI and present only for a finite time interval. The noise is assumed additive, zero mean, statistically independent from the signal, and present for an infinite time. The noise also is assumed covariance stationary with a specified auto correlation function. Enhancement is defined as the ratio of the increase in average signal power to the increase in average noise power due to integration. The results are general in that the enhancement is derived in terms of the autocorrelation coefficients of the input noise. Plots of enhancement versus number of signal observations and feedback gain are shown for uncorrelated and exponentially correlated noise. The plots show graphically the optimum choices of feedback gain and number of signal observations for a specified auto correlation function and signal observation time. When strongly correlated noise, characteristic of 10-GHz backscatter from salt flats at low incidence angles, rather than uncorrelated noise is assumed present at the input of the DLI, an example, using DLI parameters typical of modern airborne radars, shows a degradation in the maximum achievable enhancement of 9 dB.