Swashplate
You can't 'broadcast the signal in antiphase' unless you know the precise phase and amplitude of the signal at the receiver's antenna *and* can calculate the path budget instantaneously to generate the exact opposite at the receiver. Due to little problems like the speed of light, this is unfortunately impossible...
If you want to jam a signal, the only two ways to do it are to generate some sort of false signal that the receiver preferentially receives, or to put so much energy into the appropriate part of the spectrum that the receiver is unable to distinguish the wanted signal. Neither is easy, and in many cases both are effectively impossible or vulnerable to countermeasures.
R