A 107 pJ/b TX 260 pJ/b RX Ultralow-Power MEMS-Based Transceiver With Wake-Up in ISM-Bands for IoT Applications

This article presents an ultralow-power (ULP) microelectromechanical system (MEMS)-based phase-tracking frequency shift keying (FSK) transceiver (TRX) with an embedded envelop detector-based on-off keying (OOK) wake-up receiver (WuRX). The system supports a shared antenna interface of FSK-matched filter for TRX and a matching network for the FSK receiver (RX) and OOK WuRX. To consume less power, the transmitter employs an adaptive fast switching (AFS) technique for FSK/OOK modulator and uses a high-Q MEMS resonator to get frequency stability. In addition, for better interference filtering, the MEMS-based modulator is shared to provide LO in FSK RX as it owns inherent sidelobe suppression. To support higher blocker/interference rejection with relatively low power, MEMS-based FSK-matched filter plus matching network with current-reuse LNA is co-designed to provide additional passive gain. Fabricated in 65-nm CMOS process, the transmitter (TX) generates FSK signals of -11.2 dBm output power at ISM-915 MHz and the data rate is up to 6 Mb/s. At 1 MHz offset, the measured phase noise (PN) is -140.2 and -139.3 dBc/Hz at 926.3 and 932.4 MHz, respectively. By sharing the modulator, the RX exhibits -36.2 dB in-band signal-to-interference ratio (SIR), -77.5 dBm sensitivity at bit error rate (BER) of 10(-3) working under 2 Mb/s data rate. The TX, FSK RX, and WuRX consume 642 mu W@6 Mb/s, 520 mu W@2 Mb/s, and 86 mu W@200 kb/s, leading to the energy efficiency of 107, 260, and 430 pJ/b, respectively. The proposed TX achieves over 1.5x better energy efficiency than state-of-the-art results and the FSK RX attains the best FoM with the sensitivity of -77.5 dBm, which are well suited for energy-efficient pico-IoT applications.