Drone recognition has become a topic of increasing concern for defense applications. Due to the high speed of rotation of the drone blades, however, accurate drone recognition relies on sufficient time-frequency resolution of the drone radar micro-Doppler signature. Although one of the more commonly used time-frequency transforms is the spectrogram, such classical estimators embody a sub-optimal trade-off in temporal resolution versus frequency resolution. In this work, we evaluate the efficacy of various time-frequency transformations based on the latent space of deep neural networks (DNNs). In particular, we consider alternatives to the short-time Fourier transform, such as the wavelet transform, Wigner-Ville distribution, Choi-Williams distribution, and and super-resolution techniques, which have been recently shown to be effective on non-radar datasets, such as superlets. Transforms are compared for various millimeter wave radar systems for DNN-based classification.
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