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In this work, we analyze the sea clutter data collected simultaneously by the bistatic and monostatic nodes of a S-band netted radar system. The analyzed radar system is the NetRad, developed by the University College London (UCL) and the datasets were collected with four different out-of-plane geometries. The aim of the analysis is to compare statistically the behavior of the bistatic and monostatic sea clutter for different geometries. In particular, we focus on the sea spikes, whose presence increases the probability of false alarm of the radar detector. The statistical analysis is carried out by comparing the empirical distribution of sea clutter data with some known heavy-tailed distributions and by studying the behavior of three statistical parameters, the kurtosis the Weibull and K+Noise shape parameter. An algorithm that separates the sea spikes from the Bragg background is implemented, in order to study in-depth the sea spikes statistics. To this aim, we examine the empirical distribution of the spike duration and of the interval between two subsequent spikes. The results of our analyses show that spikiness is higher for low values of the bistatic angle and that bistatic data are sometimes less spiky than monostatic ones only for horizontal polarization.

This paper describes some key ideas and applications of cognitive radars, highlighting the limits and the path forward. Cognitive radars are systems based on the perception-action cycle of cognition that sense the environment, learn from it relevant information about the target and the background, then adapt the radar sensor to optimally satisfy the needs of their mission according to a desired goal. The concept of cognitive radar was introduced originally for active radar only. In this paper we describe how this paradigm can be applied also to passive radar. In particular, we describe (i) cognitive active radars that work in a spectrally dense environment and change the transmitted waveform on-the-fly to avoid interference with the primary user of the channel, such as broadcast or communication systems, (ii) cognitive active radars that adjust transmit waveform parameters to achieve a specified level of target tracking performance, and (iii) cognitive passive radars, that contrary to the active radars cannot directly change the transmitted waveforms, but can instead select the best source of opportunity to improve detection and tracking performance.

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In recent times, considerable advances have been made on analysing low grazing angle radar sea clutter in the gigahertz frequency range. In this work, a set of coherent and polarimetric sea clutter data is analysed focusing on the statistical and spectral properties of the spikes, whatever is the physical phenomenon that generates them. Using three sea spike defining parameters, the spike amplitude, the minimum spike width and the minimum interval between spikes, it is possible to identify the spiking events from the background. This work shows a sample of results from a statistical and spectral analysis of a set of sea spikes selected from the radar returns, focusing on their Doppler properties, the spike duration and the temporal interval between spikes