Active antenna using a parasitic element

Recently, various methods of using millimeter wave communication systems ha ve attracted attention. Of these, the active antennas consisting of active circuits and antenna elements integrated together have been studied widely. In particular, the active antenna combining an oscillator using FETs has a high degree of importance due to its advantage of low loss in the feed lin e. However, the Q of the active antenna combining an oscillator is degraded for the oscillator since the Q of the planar antenna connected to the FET is low. In this paper, an active antenna is proposed in which a half-wave d ipole parasitic element is placed between the gate and the drain of the osc illator made of an FET and a coplanar waveguide. An experimental investigat ion is carried out for enhancement of the stability of the oscillation freq uency and improvement of the radiation pattern by means of the parasitic el ement. (C) 2001 Scripta Technica.