Cognitive radar waveforms for frequency dense environments

A wideband cognitive radar operating in spectrally dense environments needs to use special adaptive waveforms, in order to mitigate the effect of the interferences caused by a number of concurrent narrow band communication services. In the literature, the use of adaptive waveforms with spectral nulls has been proposed. This solution, however, presents some drawbacks in case of high level of spectrum congestion. In fact, due to the high number of frequency nulls, the zero Doppler uncertainty function of the received waveform can result to be corrupted by a high number of sidelobes. This paper proposes and evaluates the use of a new family of waveforms, defined as Adaptive Frequency Modulated Waveforms (AFMWs), whose structure is the combination of a Linear Frequency Modulated Waveform with an Adaptive Stepped Frequency Waveform. A practical implementation of a Cognitive Radar tailored to a specific case study of interest is discussed and the relative performance evaluation results are presented, with regard to detection and recognition capabilities. The results demonstrate that the AFMWs are much better suited to the tasks of detection and recognition than other types of waveforms.