The Yagi antenna works like this (in the case of a three-unit antenna) : the Redirector is a little less than half the wavelength, the main oscillator is a little more than half the wavelength, and the reflector is a little more than half the wavelength, the two oscillators are separated by a quarter of a wavelength. At this time, the inductor is“Capacitive” to the induction signal, the current is 90 ° ahead of the voltage; the electromagnetic wave induced by the inductor will radiate to the main oscillator, the radiating signal travels a quarter of a wavelength, so that a 90 ° delay cancels out the“Lead” caused by the previous one. The two phases are the same, so the signal is superimposed and strengthened. The reflector is slightly longer than half of the wavelength and is inductive, with a current lag of 90 ° and a delay of 90 ° in the process of radiating to the main oscillator. When one direction is strengthened and the other is weakened, there is a strong directionality. The same is true for the process of emission state interaction.