Detection and estimation of non-cooperative uniform pulse position modulated radar signals at low SNR

In electronic warfare (EW) receivers, especially in the electronic intelligence (ELINT) receivers, The conventional and common used way of signal processing in these receivers is to detect and estimate signals pulse by pulse at high or moderate SNR. In this paper, we propose a new method to deal with the non-cooperative radar pulse train, or in another name, the uniform pulse position modulated (PPM) signal, which is a kind of LPI signal that has been used in many radar systems. Different from the conventional pulse-by-pulse method, we deal with the several pulses in the PPM radar signals at the same time. When the signals are intercepted, we firstly use fast Fourier Transform (FFT) to estimate the carrier frequency and possible limits of the pulse widths (PWs) of the PPM signals. Next, we select a group of PWs to construct two groups of matched filters with different initial phase. Then we filter the PPM radar signals using these filters and search the best one to estimate the pulse width and time of arrivals (TOAs). Although the matched filter we get may be suboptimal, the gain we get in the SNR is enough for us to detect the weak pulses and estimate the parameters.