Low-Power Frequency-to-Digital-Converter for a 6-Axis MEMS Frequency-Modulated Inertial Measurement Unit

The work presents and characterizes a frequency digitization circuit used in a multi-parameter, multi-axis inertial measurement unit wholly based on frequency modulated (FM) sensors. With a low quantization noise of 35μHZms at 100-Hz output data rate, and a linear full-scale of 1 kHz, the proposed frequency to digital converter (FDC) achieves 149 dB of dynamic range, referred to a 50 Hz sensing bandwidth. The circuit operation is successfully demonstrated on both Lissajous FM gyroscopes and time-switched FM accelerometers, on both in-plane and out-of-plane sensing axes.