Plasma lamps have a high luminous efficiency. The plasma is microwave-induced. As an advantageous result, the bulb has no electrode, thus a quasi infinite life time. A second consequence is that half of the consumed energy is dissipated upstream the bulb by the ballast, mainly by the source of microwave (magnetron). By placing this part behind a false ceiling, we will thus cut down by half the cooling load due to lighting. But to reach this goal, the bulb has to be split off the ballast. In this purpose, a coaxial cable is used to transfer the microwave energy. This introduces however a dissipation that makes difficult the ignition of the lamp because the gas discharge breakdown in the bulb results from electromagnetic resonance. Even though the cable and the bulb coupling have been tuned to the magnetron frequency, no discharge appeared in continuous supply mode. But the ignition is obtained thanks to our new modulator, which is based on a solid-state switch of large bandwidth, by pulsing the magnetron. At a frequency of a few hectohertz with a duty cycle of 10% the lamp is ignited in less than a decasecond.