English title

In a dense modern electronic warfare environment, there are a lot of radar signals. Pulse repetition intervals of signals received from radars can have various modulations and levels. It is very important to recognize these modulations and to determine their levels in electronic warfare support systems. In this paper, a method of estimating PRI levels is proposed. The extensions of the biased autocorrelation functions of the PRI sequences are derived and a new method of recognizing PRI modulation type and its levels is proposed which is based on the properties of the biased autocorrelation function of the PRI sequences and their hierarchical clustering. The performance of the proposed method has also been evaluated in a simulation scenario.