Compare QPSK, 16QAM and 64QAM constellations, and explain why the anti-jamming ability becomes worse with the increase of constellation points in each quadrant.

Answer: The constellation diagrams of QPSK, 16QAM and 64QAM are shown in Figure 7.3. 1 1. As can be seen from the figure, each quadrant of QPSK modulation has only one constellation point, while each quadrant of 16QAM and 64QAM constellation has four and 16 constellation points respectively. With the increase of constellation points, the interval between constellation points becomes denser and denser, and the amplitude and angle difference between them becomes smaller and smaller after signal modulation, which makes it more and more difficult for the receiver to judge and the possibility of error becomes greater and greater.