Phase-noise measurement in dual-mode SC-cut crystal oscillators

This paper reports the phase-noise characteristics and their analysis model of an SC-cut dual-mode oscillator. The C-mode phase-noise sideband levels of -124 dBc at 10 Hz and 154 dBc at 10 kHz have been demonstrated using a dual-mode oscillator with a 10 MHz 3rd overtone SC-cut crystal resonator. These levels are not especially low but they are only 3 to 6 dB higher than the corresponding levels of the signal obtained by the single-C-mode oscillation using one active circuit. It is therefore evident that the proposed dual-mode oscillator can be used as a reference oscillator in communication systems. Moreover, the phase-noise levels of the C-mode in the dual-mode oscillation correspond well to those obtained at stopping the B-mode oscillation. These results demonstrate that the B-mode oscillation does not disturb the phase-noise sideband levels of the C-mode signal.