Fig. 1. Heatmap of 32APSK signal constellation points in different coordinate systems

Fig. 2. Schematic diagram of the BiGRU algorithm

Fig. 3. System principle diagram of coordinate transformation+BiGRU

Fig. 4. Experimental setup and actual picture

Fig. 5. The relationship between BER and Vpp

Fig. 6. The performance of loss-training epochs

Fig. 7. Confusion matrices of model predictions using IQ coordinate and coordinate transformation training methods

Fig. 8. Comparative classification accuracy of two methods in different regions