The differential-phase method for Jicamarca F region density measurements has been modified to fit the real and imaginary components of the cross-correlation of orthogonally polarized radar returns. The original method <Kudeki et al., 2003; Feng et al., 2003> based on fitting the cross-correlation phase could only make use of correlation data from lower F region heights since the phase noise in low-SNR upper F region returns is typically non-Gaussian. However, upper F region correlation data become useful in the modified method since the fluctuations in real and imaginary parts of cross-correlation remain Gaussian even under low-SNR conditions.