Pedram Lajevardi

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BASc, University of British Columbia, 2004
MSEE, Stanford University, 2006
Admitted to Ph.D. Candidacy: 2005-2006

Research: Dynamic Offset Cancellation of Inertial Sensors

Today’s inertial sensors suffer from input offsets that drift over time, and nonlinearly change with temperature. The focus of this research is to cancel sensor offset due to bond-wire capacitance mismatch in a MEMS accelerometer, as a particular case. A new technique has been studied that measures the offset during normal operation by modulating spring-constant of the sensor (K-modulation block). The figure below shows the block diagram of the system that is being developed. There are two feedback loops in this system. The first is a commonly-used sigma-delta loop around the sensor element: from the “C to V” block to DOut through the “Switches” block back to the “C to V” block. This loop cancels the net average force on the sensor element by means of the electrostatic force, and therefore, improves linearity and dynamic range of the sensor. The second loop goes from the “Integrator” block to DOut through the FPGA (“Decimator” and “Correlator” blocks) back to the “Integrator” block. This is a very slow loop that extracts and suppresses out-of-band tones induced by the “K-modulation” block. Since the amplitudes of the out-of-band tones are proportional to the input offset, suppressing these tones also suppresses the sensor offset. A CMOS chip was fabricated in 0.18µm technology and is currently being tested.

Pedram diagram.JPG

Email: pdrm AT stanford DOT edu


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