Helicopter Classification Using Time-Frequency and Tomographic Imaging Techniques

Helicopter targets, due to its low altitude flying, are mostly detected at short ranges. Radar systems capability to classify them to a particular class or model based on the returned radar signal characteristics of the main rotor blades, enables the operator to take early and confident decisions. This paper presents the L/N quotient method for classification and two different algorithms, joint Time-Frequency analysis and Tomographic imaging techniques, to estimate the required parameters from the return signals. In joint time-frequency analysis for blade flash detections, we used only two filter outputs from STFT of target radar returns and inverse Radon transform for the tomographic imaging algorithm. Both the algorithms are evaluated for different numbers of blades using a lab fan setup.