Nathan Pletcher

A 2GHz 52 μW Wake-Up Receiver with -72dBm Sensitivity Using Uncertain-IF Architecture

A wake-up receiver (WuRx) is used in wireless sensor networks (WSN) to detect wireless traffic directed to a nodes receiver and activate it upon detection, improving network latency and energy dissipation by maximizing data transceiver sleep time. The always-on nature of the WuRx sets a power dissipation floor for the entire system. In realistic WSN scenarios, the adoption of a WuRx leads to energy savings only if it can be realized with about 50muW of power dissipation in Lin, E.Y., et al, (2004), testing the limits of low-power receiver design. While diode detectors provide for the simplest detector structure, such receivers are strongly gain-limited due to the thresholding effect of the nonlinear detector in Pletcher, N., et al, (2007) and adding gain at RF to improve sensitivity only increases power consumption. A more attractive approach is to adopt a heterodyne architecture, where the extra gain needed for robust energy detection can be obtained at an intermediate frequency (IF) with a much lower power cost. However, a survey of previous receiver designs for WSN reveals that the power requirements of the required local oscillator (LO) exceed the total power budget of the WuRx in Otis, B., et al, (2005).

A 65 μW, 1.9 GHz RF to digital baseband wakeup receiver for wireless sensor nodes

A complete 1.9 GHz receiver, with BAW resonator-referenced input matching network, is designed as a wakeup receiver for wireless sensor networks. The 90 nm CMOS chip includes RF amplifier, PGA, ADC, and reference generation, while consuming 65 μW from a single 0.5 V supply. The input RF bandwidth of the receiver is 7 MHz, while the maximum data rate is 100 kbps. When detecting a 31-bit sequence, the receiver exhibits -56 dBm sensitivity for 90% probability of detection.

An ultra-low power MEMS-based two-channel transceiver for wireless sensor networks

This paper explores the design and implementation of a low-power two-channel transceiver using micromachined resonators. Wireless sensor networks require transceivers that are small, cheap, and power efficient. RF-MEMS resonators are utilized to accommodate these constraints. The prototype 1.9GHz transceiver, designed in 0.13 /spl mu/m CMOS, operates at 1.2V and consumes 3mA in receive mode and transmits 1.6dBm with 17% efficiency. The two 40kb/s channels achieve a sensitivity of -78dBm with a 10 /spl mu/s receiver start-up time.

Ultra-low-power design

In this article, we describe how such an integrated approach has indeed made it possible to produce a PicoNode that meets the original goals. The resulting node combines innovative technologies, such as radio-frequency microelectromechanical systems (RF-MEMS) with ultra-low-power RF and digital integrated circuit (IC) design, and employs aggressive energy-scavenging and packaging techniques. For these technological advances to come to their full fruition, they must be complemented by novel opportunistic networking and wireless protocol schemes that virtually eliminate standby power while still providing robustness

PicoCube: a 1 cm 3 sensor node powered by harvested energy

The PicoCube is a 1 cm3 sensor node using harvested energy as its source of power. Operating at an average of only 6 uW for a tire-pressure application, the PicoCube represents a modular and integrated approach to the design of nodes for wireless sensor networks. It combines advanced ultra-low power circuit techniques with system-level power management. A simple packaging approach allows the modules comprising the node to fit into 1 cm3 in a reliable fashion.

Circuits and Technologies for Wireless Sensor Networks

Successful deployment of wireless sensor and actuator networks in sufficient numbers to provide true ambient intelligence requires the confluence of several disciplines including networking, low power RF and digital IC design, MEMS techniques, energy scavenging, and packaging. Progress in each of these areas has been documented and proof- of-concept prototypes have been tested. Research in RF transceiver design utilizing bulk acoustic wave resonators has yielded fully integrated, ultralow power transceivers. Novel digital circuit design techniques, including aggressive power management, robust subthres- hold logic operation, and ultralow voltage SRAM with data retention enable efficient computation. These technological advances should be accompanied by novel opportunistic networking and media access techniques to provide robustness and decrease the duty cycle of the node. Future challenges include the integration of a sub-50 mW carrier sense detector for asynchronous and non-beaconed receiver wake-up, efficient hybrid energy scavenging power generation, and cheap, robust three-dimensional packaging techniques.

Short Distance Wireless, Dense Networks, and Their Opportunities

Summary form only given. The availability of wireless transceivers transmitting over ranges from few microns to less than half a meter opens the door for a wide range of exciting new applications, ranging from seamless system assembly, smart surfaces, healthcare monitoring and intelligent machinery and components. However, the implementation challenges in terms of size and power for most of these applications are pushing the limits. Fortunately, by exploring the wide range of options offered to the designer, extremely small and virtually zero-power transceivers are feasible. This paper discusses the opportunities, challenges and options of short distance wireless, and illustrates the proposed techniques with several design examples. In addition, the challenges that emerge when trying to embed these nodes into very dense networks are explored. Special consideration is given to the issues of distributed synchronization, localization and robust communication.

CIRCUITS AND TECHNOLOGIES FOR WIRELESS SENSING

This work describes ongoing research into system architectures, circuit design techniques, and new technologies applicable to low power wireless sensing. We will present completed proof-of-concept research as well as propose ideas for future architectures. It is shown that MEMS-based transceiver blocks in combination with a dedicated carrier sense receiver can substantially reduce the communications energy of a sensor network. Additionally, novel methods for power regulation and modular packaging will be introduced.