In this paper, the design theory of an 8 GHz oscillator with a new structure of active dielectric resonator (DR) is presented. The new structure emphasizes on phase noise reduction by using only one active device. The proposed structure uses additional feedback from transistor to resonator in order to increase the quality factor. Measurement results report that phase noise is reduced to −145.19 dBc/Hz at 100 kHz offset frequency which represents 12 dB improvement compared with oscillators with passive DR. Also, in comparison with conventional active resonator oscillators, noise source of the second amplifier which makes spurious oscillation is removed. The size and power consumption are reduced due to the use of a single transistor. This structure has the lowest phase noise in comparison with other DR oscillators. In order to implement the proposed oscillator, a circuit including amplifier, resonator, coupler, and phase shifter is designed and realized.
