A variable phase-shifting system, able to generate phase-shifted replicas of the same reference input signal, has been designed to properly feed the antenna system within a plasma device. The system is based on a phase-locked loop used as a voltage controlled phase shifter and is able to provide four phase-shifted output signals. The phase differences between adjacent outputs can be varied between 0° and 100°, and are maintained equal to each other, with a precision of less than 3° in the range 2.5–10 MHz.