Joint utilization of incoherently and coherently integrated radar signal in helicopter categorization

Radar signal based helicopter categorization is a challenging task for all types of radars. Airborne pulse Doppler radar with an appropriate digital signal processing unit has a good potential to perform categorization or even classification, providing that radar parameters are carefully selected. This paper presents a helicopter categorization method, which is based on estimation of the main rotor blade tip velocity and the time interval between two successive main rotor blade flashes. Both incoherent integration and conventional coherent integration play an important role in the new method. Joint utilization of both integration types makes the method feasible without using unrealistic radar waveform parameters. Based on the L/N-quotient helicopter classification method, a new categorization procedure was developed. Compared to the original L/N-quotient method, the new method exploits both incoherent and coherent integration. Combined use of both integration types enables it to use effectively potential of dwell time and PRF. In addition, the new method includes a certain kind of moving windows edge detection algorithm that was found to improve the performance of the edge detection compared to the one introduced with the original L/N-quotient method.