Parameter Estimation of LPI Radar in Noisy Environments using Convolutional Neural Networks

Abstract: Low-probability-of-intercept (LPI) radars are notoriously difficult for electronic support receivers to detect and identify due to their changing radar parameters and low power. Previous work has been done to create autonomous methods that can estimate the parameters of some LPI radar signals, utilizing methods outside of Deep Learning. Designs using the Wigner-Ville Distribution in combination with the Hough and the Radon transform have shown some success. However, these methods lack full autonomous operation, require intermediary steps, and fail to operate in too low Signal-to-Noise ratios (SNR). An alternative method is presented here, utilizing Convolutional Neural Networks, with images created by the Smoothed-Pseudo Wigner-Ville Distribution (SPWVD), to extract parameters. Multiple common LPI modulations are studied, frequency modulated continuous wave (FMWC), Frank code and, Costas sequences. Five Convolutional Neural Networks (CNNs) of different sizes and layouts are implemented to monitor estimation performance, inference time, and their relationship. Depending on how the parameters are represented, either with continuous values or discrete, they are estimated through different methods, either regression or classification. Performance for the networks’ estimations are presented, but also their inference times and potential maximum throughput of images. The results indicate good performance for the largest networks, across most variables estimated and over a wide range of SNR levels, with decaying performance as network size decreases. The largest network achieves a standard deviation for the estimation errors of, at most, 6%, for the regression variables in the FMCW and the Frank modulations. For the parameters estimated through classification, accuracy is at least 56% over all modulations. As network size decreases, so does the inference time. The smallest network achieves a throughput of about 61000 images per second, while the largest achieves 2600.