BIAS CORRECTION AND FORWARD-BACKWARD AVERAGING IN FREQUENCY DOA TRACKING PROBLEMS/

In this paper, we discuss some issues relevant to frequency and direct ion of arrival (DOA) tracking problems. First, we develop a linear Fre quency Modulated (FM) signal model for accurately describing windowed, slowly time varying narrowband signals that typically occur in tracki ng problems. We then derive first order bias expressions for the peak locations of a Discrete Time Fourier Transform (DTFT) spectrum of a wi ndowed, slowly time varying linear FM signal. We also show that Forwar d-Backward (FB) averaging is generally inappropriate for nonstationary data, but that it is appropriate when applied to tracking the frequen cies of windowed, slowly time varying narrowband signals. A major moti vation for using FB averaging is to increase the efficiency of subspac e based frequency/DOA estimation in tracking problems. Finally, simula tions confirm our first order bias expressions, and show that FB avera ging does not significantly alter (or degrade) the time varying MUSIC based frequency estimation performance over that of Forward only avera ging.