Two helicopter classification methods with a high pulse repetition frequency radar

In this study, two helicopter classification methods with a high pulse repetition frequency radar are proposed. By analysing the returned signal from a main rotor, the authors find that the essential difference between rotors appears when none of blades is orthogonal to the incident waves. Based on this difference, the authors propose two methods to classify the helicopter. The first one is based on the matched filters (MFs), including the time MF and the time-frequency MF. The second one derives from time-frequency masks. Experimental results demonstrate that both methods have the ability to classify helicopters with the same micro-Doppler parameters at a low signal-to-noise ratio. And they are robust against errors of the estimated parameters and the gesture of the helicopter.