Design of a K-band push-push VCO using GaAs MESFET varactor

The K-band oscillator is useful for point-to-point communication, narrow band microwave wireless LAN (Local Area Network), and wireless CATV. It is very hard to obtain this range of signal by single oscillator due to its limitation of fabrication for hybrid microwave integration circuit. To overcome this problem, the push-push structure which is one of many techniques is used. To improve the output power of an oscillator, the push-push oscillator is implemented on the harmonic oscillator type transforming conventional oscillator. Since each oscillator is designed as a second harmonic oscillator, the output power and the suppression of the fundamental frequency component are improved. An active resonator (AR) using FETs has also been proposed for high performance microwave oscillators. In this paper, an AR is used by the combination of a three-terminal GaAs MESFET varactor and a microstrip hairpin resonator. A MESFET varactor has high tuning speed and low tuning power. It is applied to the design of a K-band push-push VCO (voltage controlled oscillator).