The paper considers the simulation results of an oscillating system with a dielectric resonator at 10 GHz. The model was designed using CAD simulation in HFSS. The oscillating system with a dielectric resonator in a metal cavity is considered. To minimize the phase noise of the oscillator, the resonator must be designed to have a high quality factor. The high quality factor is obtained by using the dielectric resonator in a metal cavity. Three types of metal cavities are analyzed and the parameters affecting their quality factor and losses are identified. The compact design of the resonator excited from the end face for the oscillator in hybrid form and the results of modeling and measuring the characteristics of the oscillating systems are given. Using these results, the phase noise level which can be reached in oscillators was assessed. With the dimensions of the aluminum cavity of the oscillating system of 28×8 mm and the inherent Q-factor of the DDR equal to 10000, using low-noise SiGe bipolar transistors in the self-excited oscillator, it is possible to reach the phase noise level of –130 dB/Hz at the analyzed frequencies of 10 kHz.