System and method for processing capacitive signals
A sensor assembly for sensors such as microfabricated resonant sensors is disclosed. The disclosed assembly provides improved performance of the sensors by providing a thermally insensitive environment and short pathways for signals to travel to processing components. Further, the assembly provide modular construction for the sensors and housing modules, thereby allowing replacement of the sensors at a lower cost. The assembly includes a sensor module including a sensor formed on a conductive substrate with a cavity formed on one surface. The substrate has conductive vias extending from the cavity to a second surface of the substrate. A housing assembly accommodates the sensor and includes a rigid housing, preferably made from a ceramic. An electronic component, such as an amplifier, is mounted on the rigid housing. The electronic component electrically engages the vias substantially at the second surface of the substrate. The electronic component receive signals from the sensor through the vias. The signals are then processed through an amplifier and a digital signal processor using a modified periodogram.
1 . An electronic component for processing a capacitive signal superimposed with a drive signal, comprising:
a phase compensation stage adapted to compensate for phase variation caused by parasitic capacitances, said phase compensation stage being gate-to-source bootstrapped through a low-input-impedance component; and
an impedance matching stage adapted to compensate for amplitude variations caused by said phase compensation stage.
2 . The electronic component according to claim 1 , wherein said low-input-impedance component is a MOSFET
3 . The electronic component according to claim 2 , further comprising:
a Miller capacitance compensation stage adapted to compensate for Miller capacitance caused by the MOSFET, the Miller capacitance compensation stage being double bootstrapped through the MOSFET.
4 . A method of processing a capacitive signal, comprising:
generating a superimposed signal by superimposing a drive signal on said capacitive signal;
directing the drive signal to a modulator for generating a phase-shifted signal, said phase-shifted signal being 180-degree shifted;
directing said phase-shifted signal and the superimposed signal to a MOSFET; and
isolating said capacitive signal through substantial cancellation of drive-signal components of said superimposed signal and said phase-shifted signal.
5 . A high-input-impedance, low-output-impedance electronic circuit for processing a signal from a capacitive sensor, comprising:
an electronic component having a low input capacitance for interfacing with the capacitive sensor; and
a gate-to-source bootstrapping circuit interfacing with said electronic component.
6 . The electronic circuit according to claim 5 , wherein said electronic component is a lateral DMOS device.
7 . The electronic circuit according to claim 5 , wherein said electronic component is a dual-gate CMOS device.
8 . The electronic circuit according to claim 5 , further comprising:
a Miller capacitance compensation stage adapted to compensate for Miller capacitance caused by the electronic component, the Miller capacitance compensation stage being double bootstrapped through the electronic component.
9 . The electronic circuit according to claim 5 , wherein said electronic component is adapted to function as an automatic gain controller (AGC).
10 . The electronic circuit according to claim 5 , wherein said electronic component is adapted to function as a mixer.