Analog front-end circuit for conditioning a sensor signal

A system for conditioning and detecting a sensor signal, comprising:

• a multiplier circuit for performing a multiplication operation on the sensor signal to produce a multiplied sensor signal;
• an analog front-end (AFE) circuit coupled to the multiplier circuit to produce a conditioned sensor signal from the multiplied sensor signal, the AFE comprising:
• a first stage configured to amplify and filter the sensor signal, the first stage comprising a biquadratic filter comprising a first plurality of DC-coupled transconductance amplifiers;
• and
• a second stage configured to further amplify and filter the amplified sensor signal, and to compensate a direct current (DC) offset of the first stage, the second stage comprising a second plurality of AC-coupled transconductance amplifiers, wherein each transconductance amplifier of the first plurality of DC-coupled transconductance amplifiers and of the second plurality of AC-coupled transconductance amplifiers has a programmable transconductance and comprises a plurality of subthreshold-biased transistors;
• and
• a detector circuit coupled to the AFE to determine a presence of the conditioned sensor signal.

A method for conditioning a sensor signal, comprising:

• amplifying and filtering the sensor signal using a first stage of an analog front-end (AFE) circuit, the first stage comprising a biquadratic filter comprising two Gm-C filters connected in series;
• further amplifying and filtering the amplified sensor signal using a second stage of the AFE, the second stage comprising a plurality of AC-coupled transconductance amplifiers;
• compensating a direct current (DC) offset of the first stage using the second stage, wherein the two Gm-C filters and each transconductance amplifier of the plurality of AC-coupled transconductance amplifiers has a programmable transconductance and comprises a plurality of subthreshold-biased transistors;
• and
• converting the biquadratic filter to a single Gm-C filter by turning off a quiescent current of one of the two Gm-C filters.