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.