A Technique for the Extraction of Ultra-Wideband (UWB) Signals Concealed in Frequency Band Folded Responses

Ultra-wideband (UWB) excitation sources in radar systems have allowed for enhancement in capabilities such as target spectral response, clutter suppression, and range resolution. While generation of generic UWB signals has become easily achievable, direct acquisition, or digitization, of these bandwidths (>= 4 GHz) is not. To account for this, many UWB radar systems implement a single or multi-stage band folding technique in the receiver hardware chain which allows for the direct digitization of the UWB waveform at a smaller bandwidth (e.g., 4 GHz into 1 GHz). While the lower bandwidth allows for larger than narrowband capabilities, it reduces desired features such as range resolution (e.g., 3.75 cm to 15 cm). In an effort to address this problem, and allow for utilization of full bandwidth of an UWB waveform, this paper presents a signal processing technique which utilizes hardware band folding to wrap a spectrally unique UWB multi-tone waveform into a lower frequency, lower bandwidth signal allowing for both direct digitization and conservation of UWB features. The signal processing technique utilizes the multi-tone waveform to generate an UWB signal composed of sections whose separate spectral peaks fold into the inner Delta F regions of the previous band. It will be shown, that through reassignment of these peaks, as well as the phase, to the individual frequencies, the intended UWB capabilities can be restored.