A further analysis of decorrelation performance of spatial smoothing technique for real multipath sources

The authors analyze and discuss the decorrelation performance of the spatial smoothing technique based on a first-order prediction approximation applied to time-delay narrowband signals. The analysis reveals that the decorrelation effect varies with the frequency bandwidth, arrival angles, and the time delay of the multipath sources. The study of the decorrelation performance with the frequency bandwidth provides more detail about the spatial smoothing than previous studies. When the bandwidth of the signal is zero, the proposed analysis is identical to that in the aforementioned studies. If it is not zero, the upper bound on the effective number of subarrays is about K≈0.77/FBW. The decorrelation performance is degraded when the number of subarrays added is greater than 0.77/FBW or the distance between the farthest and the reference subarrays is more than 0.385 λ/FBW, where FBW and λ denote fractional bandwidth and wavelength, respectively