A MEMS BPSK to ASK converter

The purpose of this paper is to investigate the feasibility of using micro electromechanical systems (MEMS) to convert a binary phase shift keying (BPSK) signal to a simpler amplitude shift keying (ASK) scheme.

The prototype is designed within the SOIMUMPs® fabrication process constraints. The fabrication constraints imposed geometric limitations on what could be tested. These constraints were used to build a mathematical model, which in turn was used to optimize the response using MATLAB®. The optimized design was tested using finite element analysis with CoventorWare®, and finally lab tests on the fabricated device were performed to confirm theoretical predictions.

Theoretical predictions compared well with lab measurements on a prototype device measuring 2.9 mm². The prototype was tested with a carrier frequency of 174 kHz at a BPSK data rate of 3 kHz and carrier amplitude of 6 V. With these parameters, ASK modulation indices of 0.96 and 0.94 were measured at the two output sensors.

This study provides a MEMS solution for BPSK to ASK conversion. The study also identifies what limits betterment of the modulation index and data rate. Such a device has potential application in wireless sensor network (WSN) nodes that have energy harvesters and sensors that are also built in MEMS. Being a MEMS device, it can facilitate integration in such WSN nodes and, hence, potentially reduce size and costs.