Fig. 3: Experimental results of PAFE and radar target recognition.

a–d Examples of the extracted feature maps of the target of “I”, “M”, “L”, and “C”. For each target, the first column shows four intermediate feature maps of the first convolutional layer and the second column shows four final feature maps of the second convolutional layer. Markers on the plot are the samples at 2.5 GSa/s and 1.25 GSa/s, respectively. e Loss functions and classification accuracy of transfer learning. f, g The confusion matrices of classification before and after transfer learning. h Result of t-SNE for the final feature maps, non-transferred classifier, and the transferred classifier, respectively