How to simply judge whether the measured signal of spectrometer is normal without using the function of signal source?

1, IO constellation is a modulation mapping relationship. By using the orthogonal plane, we expand all the possibilities of modulation-the number of modulated symbols (or state space) on the orthogonal plane we construct. In the process of signal modulation, jumping from one point to another (modulation state), the distance between points is called Euclidean distance, which represents energy; When we observe whether the trajectory falls on the corresponding grid points correctly, we can judge whether the amplitude and phase modulation of the signal is completed.

2.IQ eye diagram is a powerful tool to observe the change of signal digital modulation process with time. With the change of time, whether the signal modulation process is "closed" after the I-axis tracks overlap can judge the eye pattern quality of the in-phase channel. There is also a Q-eye diagram called orthogonal channel eye diagram. IQ eye diagram is the basis of error vector time measurement.