RESUMEN
With the development of signal processing technology and the use of new radar systems, signal aliasing and electronic interference have occurred in space. The electromagnetic signals have become extremely complicated in their current applications in space, causing difficult problems in terms of accurately identifying radar-modulated signals in low signal-to-noise ratio (SNR) environments. To address this problem, in this paper, we propose an intelligent recognition method that combines time-frequency (T-F) analysis and a deep neural network to identify radar modulation signals. The T-F analysis of the complex Morlet wavelet transform (CMWT) method is used to extract the characteristics of signals and obtain the T-F images. Adaptive filtering and morphological processing are used in T-F image enhancement to reduce the interference of noise on signal characteristics. A deep neural network with the channel-separable ResNet (Sep-ResNet) is used to classify enhanced T-F images. The proposed method completes high-accuracy intelligent recognition of radar-modulated signals in a low-SNR environment. When the SNR is -10 dB, the probability of successful recognition (PSR) is 93.44%.