Identification of the unmanned aerial vehicle (UAV) is a challenging problem. For identification, micro-Doppler effects from the rotors of UAVs are widely used to extract the features. Short Time Fourier Transform (STFT), Wigner-Ville distribution (WVD) and s method are the most common methods to obtain micro-Doppler signatures. Rotor blade length, number of blades and rotation rate have significant distinguishable effects on the micro-Doppler signatures. In this paper, effect of blade length, number of blades and rotation rate on micro-Doppler signatures are presented.