Aiming at the miniaturization and low phase noise requirements of microwave oscillator to the up and down frequency conversion devices operating at Ka and Ku band,using the single phase locked loop (PLL) frequency synthesizer technology, the microwave oscillator is designed and the PLL phase noise is calculated.The effect of the phase detector frequency,the phase detector sensitivity and the loop bandwidth on the output phase noise of the phase locked loop are analyzed.According to the analysis results,the microwave oscillator circuit parameters have been reasonably chosen and both low phase noise and small size have been taken into account.The test results show that the calculation and measurement of phase noise indexes agreed well and can meet the practical engineering application.