A system for detecting responses of a MEMS resonator device includes first and second signal sources, a signal divider and a frequency mixer. The first signal source provides a first signal and the second signal source provides a second signal that electrostatically drives the MEMS resonator device, causing mechanical vibration. The signal divider divides the first signal into a probe signal and a local oscillator (LO) signal, the probe signal being applied to the MEMS resonator device and reflected by a capacitance of the MEMS resonator device. A reflection coefficient is modulated onto the reflected probe signal at the mechanical resonance frequency by variations in the capacitance induced by the mechanical vibration of the MEMS resonator device. The frequency mixer mixes the reflected probe signal and the LO signal and outputs an intermediate frequency (IF) signal, which represents modulation of the reflection coefficient, providing an image of the mechanical vibration.