Improved SZ Phase Coding Weak Trip Velocity Recovery Using Regression Filter.

SZ phase coding is a signal processing technique used by the National Weather Service for separating multiple trip echoes thereby increasing the unambiguous velocity and range for pulse transmission radars. Typically, there is strong trip echo overlaid by weak trip echos. In order to estimate the weak trip velocity, the strong trip echo must be eliminated. To do this, a frequency domain 3/4 spectral notched is typically used. The SZ phase coding technique also requires a time domain window function such as the von Hann. The application of this window function effectively reduces the number of independent samples available for radar variable computation which intern increases the standard measurement error of the retrieved radar variable. In addition, if there is also ground clutter signal present, that too must be filtered. In this paper we show how the regression filter can be used to eliminate both ground clutter and the strong trip echo. The resulting weak trip velocity estimates show a significant improvement over the currently used NEXRAD SZ processing algorithm. Experimental NEXRAD data are given that demonstrate the improved weak trip velocity recovery.