Very-low phase noise RF-MEMS reference oscillator using AlN-on-Si resonators achieved by accurate co-simulation

Reference oscillators are crucial hardware components of radio-frequency receiver circuits, as their performance directly affects the system performance. Especially in GHz applications, such as 4G/5G mobile communications, a low error-vector magnitude is required, which is strongly influenced by the phase noise of the reference oscillator. This paper reports the results of the design, simulation, and measurement of a MEMS oscillator with very low phase noise. Therefore, it is suitable for use as reference oscillator operating at high frequencies in RF receiver systems. While the MEMS device is a plate-shaped contour-mode resonator in an aluminium-nitride-on-silicon technology, the active part of the oscillator is designed and fabricated in a 180 nm CMOS technology. By adding the parasitic effects of the assembly, taken from measurements of the submodules, the results from system simulation and measurement show good agreement, i.e. only 3 dB deviation in the noise floor of −142 dBc/Hz. The phase-noise level of the oscillator at an offset of 1kHz from the operating frequency of 256 MHz is −112 dBc/Hz, among the lowest values reported for MEMS-based oscillators at this high frequency.