Introduction to standing wave
A standing wave is a distribution state formed along a transmission line by two waves of the same frequency and opposite directions of transmission (not necessarily electric waves). One of the waves is generally the reflected wave of another wave. An antinode appears at a point where the voltage (or current) is added, and a node is formed at a point where the voltage (or current) is subtracted. On the waveform, the position of the nodes and antinodes is always constant, giving the impression of “standing still”, but its instantaneous value changes with time. If the amplitudes of the two waves are equal, the amplitude of the nodes is zero.