1 MHz Modulation Frequency 28 nm CMOS 1ng Sensitivity Analog Front-End for Nanogravity Accelerometers in Aerospace Applications

Accelerometers in microgravity environments are stimulated by very weak (nm/s2) and very low frequency (< 1 Hz) accelerations, which are therefore very difficult to detect. Thus, the signal processing chain driven by the accelerometer operates at frequencies higher than the band of the 1/f noise as in classical amplification stages. For these reasons the state-of-the-art solutions are often based on analog continuous-time Mixers adopting specific technological choices such as: electrical off-the-shelf transformers directly coupled to the accelerometer and almost flicker-free junction/bipolar Transistors Low Noise Amplifiers. Obviously, this approach severely limits the possibility of miniaturizing analog front-ends disabling the scaling down of the electronic silicon integrated systems. This paper definitively solves the previous problems, proposing a signal processing technique that allows the integration of the front-end in nmrange scaled-down technologies (28 nm CMOS). Specifically, this article focuses on design and development of an analog frontend system composed of an Accelerometer, a (passive) Mixer and a Low Noise Amplifier that allows the reconstruction of signals of the order of 10 nm/s2 on bands of the order of a few Hz. The proposed Nanogravity Accelerometer Analog Front-End (nG-AFE) exhibits 53 dB gain (nm/s2 to V) at 1nm/s2/√Hz Equivalent acceleration noise Power Spectral Density, performing a final (after digital signal processing reconstruction) 23.5 dB Signal-to-Noise Ratio at 10 nm/s2 minimum input acceleration.