Consult and ask for help

[2017wxyzwxyz]

Hello, jingw2：
I use matlab 2020 official deep learning example code (LSTM) to do time series data prediction, the result is that I have not learned the characteristics of the amplitude change of the original signal, but learned the quasi periodic characteristics, as shown in the figure:
overview picture

Details of the picture

Is this pure signal data time series suitable for deep learning prediction?

     I  want to improve the prediction accuracy，For example, the prediction accuracy is increased from RMSE = 289 to RMSE = 220？Please give me your advice，thank you very much！

best wishes,
Mr.Wang