Helicopter Main and Tail Rotor Blade Parameter Extraction Using Micro-Doppler

The rotating structures on an airborne target cause additional Doppler modulation in the return signal which is known as the micro-Doppler effect. Information regarding the rotating structures can be extracted from this effect. A technique based on time-frequency transform and Inverse Radon Transform (IRT) to extract helicopter main and tail rotor blades parameter for the purpose of target recognition is investigated. Inverse Radon transform is performed on the spectrogram of simulated signals for different frequencies. A mathematical model to simulate the micro-Doppler effects from the helicopter considering both main and tail rotor blades was developed. The proposed algorithm shows that transformed images corresponding to the main and tail blade's rotation rates are well focused. The focused image is chosen by calculating the concentration measure of the inverse Radon transformed images. Also blade parameters like the number of rotor blades, the blade length and the rotation rate of the helicopter's main and tail rotor can be obtained from IRT image.