Enhanced detection of orthogonal radar waveforms using time-frequency and bi-frequency signal processing techniques

Abstract

This thesis investigates the periodic autocorrelation function (PACF) and periodic ambiguity function (PAF) for orthogonal continuous waveform (CW) modulations used in netted low probability of intercept (LPI) radar. Three orthogonal polyphase sequences and one frequency coding sequence are examined and their PACF and PAF characteristics are quantified. The Wigner-Ville distribution (WVD) and quadrature mirror filter bank (QMFB) timefrequency signal processing techniques and the cyclostationary bi-frequency technique (often used in non-cooperative intercept receivers) are used to detect the orthogonal CW signals and extract their parameters. The results shows that a combination of the techniques used were able to extract the basic signal parameters of bandwidth and code period from the polyphase waveforms and also the frequency hop slots and code length from the frequency coding sequence. The concept of using a swarm of unmanned aerial vehicles (UAV) is examined from the viewpoint of a coordinated group of netted intercept receivers in search of an LPI radar network.