Abstract: The design and experiment of a simple microwave VCO with high performance is presented in this paper. This VCO which has the characteristic of high price/ performance ratio was designed based on the principle of negative resistance, utilizing microwave FET and varactor diodes in the circuit. In the design process, ADS was used for circuit matching and optimization. A proper external circuit was designed to improve tuning linearity, at the same time, the phase noise was reduced. The measured result shows that, the central frequency of the VCO is 4. 3GHz, the tuning range is more than 200MHz, the output power is higher then 5. 2 dBm. And phase noise of -112 dBc/ Hz at 1 MHz offset, -83 dBc/ Hz at 100kHz offset are achieved.