Amplitude modulation (AM) : The form of modulation.

调幅：调制的一种形式。

Mode of amplitude modulation of one channel by another.

模式的调幅一个由另一通道。

The first radio broadcasts were made using amplitude modulation.

最初的无线电广播设备采用的是波幅调制。

This modulation include either amplitude modulation or frequency(phase) modulation.

包括幅值调制和频率（相位）调制两部分。

The 4D means four data symbols (two bits), the PAM5 is Pulse Amplitude Modulation with five signal levels.

4D指四个数据符（2比特），PAM5表示分5个层级的脉冲幅度调制。