Design and Analysis o f a DCO-Based Phase- Tracking RF Receiver for IoT Applications

Abstract

This paper presents an energy-/area-efficient digitally controlled oscillator (DCO)-based phase-tracking Receiver for Internet-of-Things (IoT) applications. The RX leverages the constant-envelope nature of frequency shift keying modulation adopted in many IoT protocols, e.g., IEEE802.15.4 and Bluetooth low energy (BLE), to enhance the energy efficiency and to reduce the chip area. The proposed RX, with the DCO acting as a local oscillator (LO) and binary frequency feedback, promotes low-power and low-voltage circuit design, while a data- aided carrier-frequency tracking ensures the received carrier stability without a power-/area-hungry phase-locked loop (PLL). The RX avoids a compromise between a power-hungry I/Q LO generation and the image rejection in traditional RXs. An equivalent mathematical model is further presented, which helps to analyze and optimize the frequency response of the proposed RX. Fabricated in 40-nm CMOS, the RX consumes 1.55 mW from a 0.85-V supply and has a −87-dBm sensitivity at 2 Mb/s, which leads to a 0.77-nJ/b energy efficiency and 178-dB RX sensitivity FoM.