Ultra low power and miniaturized MEMS-based radio for BAN and WSN applications

This paper explores where MEMS devices such as BAW and low frequency silicon resonators can be used to reach further miniaturization and to lower the power dissipation of 2.4GHz transceivers targeting BAN and WSN applications. The system requirements for improving such networks are derived after analyzing appropriate low power communication protocols. A super-heterodyne transceiver architecture taking advantages of the high-Q of BAW resonators to reach lower phase noise and implement highly selective RF filters to reject interferers or unwanted IF harmonics is then presented. The design of related MEMS-based specific circuits is also discussed in details. Experimental results validate the functioning of the complete transceiver in both RX and TX modes. The measurements also demonstrate phase locking of the synthesizer to an electronically temperature-compensated low frequency silicon resonator, which is used to implement a unique ultra-low power oscillator for both RTC and reference frequency functions. Key measured features are a phase noise of -140dBc/Hz at 1MHz offset and the demonstration of 1Mbps GFSK modulation in TX. The receiver sensitivity reaches only -66dBm at 200kbps requiring further investigations to understand the reasons of the current limitation.