A biosignal analog front-end leveraging frequency translation

We propose a superheterodyne frequency mixing approach for extending the passband frequency response of existing biosensors such as neural recording devices. In this approach, we use a digital switching mixer to translate the frequency spectrum of a biological signal from its original passband to an intermediate frequency (IF). The IF signal is then amplified and digitized by an existing neural recording device, and the original signal passband is recovered by synchronous demodulation in post processing. We demonstrate this approach by translating a pre-recorded mouse electrocorticogram from a frequency range of 0.5 Hz to 100 Hz up to an IF of 407 Hz, enabling the use of an existing IC having a low frequency cutoff of 12 Hz. With an input impedance of 10 MΩ, the total root mean square error (RMSE) of the reconstructed signal is on the order of 41 μV.