Design of a low phase noise oscillator based on high Q tunable dielectric resonator

In this paper, a 3.9GHz tunable dielectric resonator oscillator (DRO) with low phase noise is presented. To minimize the phase noise of the oscillator, a high Q-factor tunable dielectric cavity resonator operating in the TE011 mode is designed. Analytical equations are derived to determine the resonant frequency of the cavity resonator. The calculated results and simulated ones by HFSS software are in agreement within 2 percent. A tuning metallic lead with threads is used to tune the first TE011 mode resonant frequency of the cavity resonator and move the spurious HE111 mode resonant frequency farther without significantly affecting the Q-factor. 13.5dB gain two stage low noise amplifier which offers a circular power 6dBm is designed to sustain the oscillator closed-loop loss. In order to occur oscillating, a mechanically tunable phase shifter is also applied. Phase noise levels of -112dBc/Hz and -136dBc/Hz are obtained at offset frequencies of 10 and 100 kHz in practical oscillator noise measurement.