A varactor-tuned active-integrated antenna using slot antenna

A varactor-tuned active antenna which consists of a series feedback voltage-controlled oscillator (VCO) and a well matched slot antenna is proposed. The fabricated antenna shows stable oscillation at 5.8 GHz band, and the frequency varied from 5.73 to 5.97 GHz, with less than 1.28 dB of amplitude deviation over the frequency range. Since the fabricated active antenna is a simple structure where the operating frequency can be easily tuned through the varactor diode, it may be used as an element in phase-shifterless beam scanning systems. In addition, a capacitor for dc blocking is not necessary due to isolation between the active and radiating element.