Physical Characteristics of a Plasma Antenna

This experimental and theoretical study examines the excitation of a plasma antenna using an Argon surface wave discharge operating at 500 MHz with RF power levels up to 120 W and pressures between 0.03 and 0.5 mb. The results show that the length of the plasma column increases as the square root of the applied power, that the plasma density decreases linearly from the wave launcher to the end of the column and that these results are consistent with a simple global model of the antenna. Since noise is critical to communication systems, the noise generated by the plasma was measured from 10 MHz to 250 MHz. Between 50 MHz and 250 MHz the excess noise temperature was found to be 17.2±1.0 dB above 290 K. This corresponds to a thermal noise source at 1.4±0.3 eV compared with an electron temperature of 1.65 eV predicted by the model.