Use of dynamic radar signature for multistatic passive localisation of helicopter

The passive radar concept is very attractive with regard to the covertness and detectability of a low-altitude flying target by use of low-frequency opportunistic signals. Detection performances are described in a large number of published papers showing the feasibility of passive detection. Accurate localisation of a target is more problematic, because it requires appropriate opportunistic signals for range compression as well as a large receiving antenna for accurate angular measurement. The introduced concept considers the exploitation of the dynamic signatures returned by helicopters to facilitate their localisation. A multistatic configuration with at least three receivers is considered. Flash echoes observed on each of the bistatic radars are detected and processed in a coherent manner to derive a set of angles used to triangulate the target position. Simulations are described including an approximate modelling of the bistatic radar cross-section. Analysis of different multistatic configurations is carried out. Further possible improvements of the concept are also introduced.