Analysis and Design of a Multi-Mode Wake-Up Receiver Based on Direct Envelope Detection in Wireless Sensor Networks

In this paper, a multi-mode ultra-low power wake-up receiver based on direct envelope detection in HF/UHF band is analyzed and presented. Narrow-band LC matching network with passive voltage gain, active common source envelope detector with high conversion gain and baseband modules with signal amplification are clarified, separately. In order to balance the power consumption and sensitivity, multi-mode with power detection (PD), signal detection (SD), and high sensitivity signal detection (HSSD) are adopted. The PD mode is used to monitor the incident radio power, while in SD/HSSD modes, the wakeup sequences of 100/10 kb/s are detected with different power consumption and sensitivity. The presented wake-up receiver prototype is fabricated in a 95-nm CMOS process with an area of 0.6*0.3 mm2. Measurement results show that the wake-up receiver achieves a sensitivity of -45/-42 dBm, -43/-40 dBm and -58/-55 dBm while dissipating 120 nW, 600 nW, and 1 μW in PD mode, SD mode, and HSSD mode, respectively, while working in the HF/UHF band, separately.

I. Introduction

With the emerging development of the Internet of Things (IoT), smart sensors and wireless sensor networks (WSN) are widely used, such as the human health monitoring system with wearable sensors [1] and the complex environment monitoring system with fixed or mobile sensors [2]. Sensing, data processing, and communication are three essential domains in WSN, where data communication occupies the majority power consumption [3]. Due to the market requirement and potential applications of internet-connected things [4], a lot of modern low power communication protocols, devices and components have been occurred and promote the development of smart wireless sensor networks [5], [6]. In each intelligent wireless sensor, communication distance, operation frequency and power consumption are significant specifications. In traditional wireless sensors, long communication distance can be achieved by adopting high-performance transceiver but with several milli-watt power consumption [7], which shortens the sensors lifetime because of the limited power capacity and volume of the battery. To solve the power consumption issue, the duty-cycled transceiver is a direct technique, but it suffers from the long communication latency, it cannot be used in the inactive nodes. Event-driven wake-up receiver (Wu-Rx) is a viable technique to scale down the standby current [8], [9] and further the average current to meet the system power requirement. Accordingly, the wake-up receiver based sensor node is shown in Fig.1. The always-on wake-up receiver monitors the ambient event with low power consumption and enables the main transceiver with partly enabled power supply, digital signal processing, memory, and sensors with small latency to be waken-up if active communication is required. Fig. 1.

Wake-up receiver based on sensor node in WSN application.