With the advent of wearable devices and the internet of things (IoT), capacitive sensors are needed to measure various physical quantities, which include motion proximity, humidity and pressure. One example is a MEMS (Micro-Electro Mechanical System) which can convert speed or angle to capacitance.
To be able to resolve small changes in these physical quantities, Capacitance-to- Digital Converters (CDCs) are required to have a very-high capacitance resolution; which can go down to sub aF range (a millionth of a pF !).
The figure shows a simplifed diagram of a capacitive-sensor system including one of the latest architectures of the CDC. It includes continuous-time capacitance to voltage converter, which converts the capacitance to be measured to a voltage. The output voltage is being processed by a low pass filter; followed by a high-pass sigma-delta ADC; which converts the voltage to digital code-word.
Goals:
- Build Matlab & Simulink model for the CDC, investigate the key parameters, and explore the effects of the non-idealities.
- Build behavioral-model for the CDC using Cadence and VerilogA-based analog hardware description & determine the specification of each sub-block in the system.
- Circuit design & transistor-level implementation of the sub blocks like (C to V converter, low pass filter, sigma delta ADC, circuits for coarse capacitance tun-ing, etc.)
What we expect:
- Good skills in Matlab and Cadence.
- Good knowledge about analog IC design and data converters.
- Organized and well documented research and dedication to successful work.