Wideband Auto-Ambiguity Function Nulling Algorithm

Abstract

This report discusses the placement of null regions on the wideband auto-ambiguity function (WBAAF). To date, the majority of papers on this subject apply the null regions to the narrow band, side lobe cancellation of the auto-ambiguity function for a radar echo pulse. By selectively placing a null region in an original waveform's WBAAF, a transmit sequence, especially a white noise radar pulse, can be tailored to lower the energy of peak regions on the WBAAF surface that might be masking desirable portions. The approach discussed in this paper is a unique iterative algorithm which we have termed the Wideband Nulling Algorithm. The Wideband Nulling Algorithm operates on time-scaled data and thus inherently utilizes a wideband approach to placing a null in the ambiguity function surface. Since the algorithm operates on the time domain series, it maps an original waveform to a new time domain waveform such that its second order statistics have a WBAAF surface containing the desired null regions. The goal is to perform this mapping operation with minimal disturbance or impact to the original signal so that the signal content or message is not disturbed. This Wideband Nulling Algorithm is an elegantly simple, mathematical process to reduce interference clutter peaks from a radar, sonar, or an ultrasound ambiguity function surface. This fundamental process has potential applications to many fields including biomedical imaging.