MULTIFREQUENCY DOPPLER - IMPROVING THE QUALITY OF SPECTRAL ESTIMATIONBY MAKING FULL USE OF THE INFORMATION PRESENT IN THE BACKSCATTERED RFECHOES

This paper investigates the application of the two-dimensional Fourier transform in the context of pulsed wave Doppler. It is shown that two -dimensional spectral analysis of the backscattered RF echoes provides individual Doppler spectra corresponding to the whole range of transm itted frequencies which can be combined, after proper scaling, to form a ''multifrequency'' spectral estimate. Theoretical expressions are d erived for the signal-to-noise ratio of the multifrequency sonogram wh ich predict substantial gains over the conventional (one-dimensional) approach for Doppler processing. These predictions are verified by mea ns of extensive simulations, which also provide an insight into the ef fect of electronic noise.