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1-V Transceiver SoC Serves Biotelemetry Applications

Wireless technology has enabled biotelemetry applications that monitor vital signs like temperature and heart rate. At the heart of these applications are wireless body sensor networks, which comprise human-body-worn sensor nodes. These networks rely on modules that gather, store, and process the patient's vital data before sending it to a central base station. For miniaturization, increased functionality, and a reduction in power consumption, however, the industry has recently been moving toward a system-on-a-chip (SoC) solution. Unfortunately, such solutions consume excessive active power. At Toumaz Technology Ltd. (Abingdon, Oxfordshire, UK), however, a 1-V RF transceiver for biotelemetry and wireless body sensor network applications has been realized as part of an ultra-low-power SoC. When that SoC is interfaced to appropriate body-worn sensors, it can perform ubiquitous medical monitoring.

This development is credited to Alan Chi Wai Wong, Ganesh Kathiresan, Chung Kei Thomas Chan, Omar Eljamaly, Okundu Omeni, Declan McDonagh, Alison J. Burdett, and Christofer Toumazou. They created a transceiver that relies on Frequency Shift Keying (FSK)/Gaussian FSK modulation at a data rate of 50 kb/s. In doing so, it provides wireless connectivity between target sensor nodes and a central base-station node in a single-hop star-network topology operating in the 862-to-870-MHz European short-range-device (SRD) and the 902-to-928-MHz North American Industrial, Scientific, & Medical (ISM) frequency bands. An on-chip, proprietary media access controller (MAC) controls the transceiver. Operating half-duplex, the transceiver achieves 102 dBm receiver input sensitivity (for a 10-3) raw bit error rate) and up to 7 dBm transmitter output power through a single antenna port.

During receive and transmit operations, the transceiver consumes 2.1 mA and as much as 2.6 mA, respectively, from a 0.9- to 1.5-V supply. This current consumption makes the SoC suitable for operation using thin, flexible printed battery technologies as well as zinc-air coin cells. The RF transceiver is realized with a digital section that consists of a full-custom hardware MAC including a frame-synchronization block (FSB) and error encoding and correction. It occupies 7 mm2 in a 4-x-4-mm2 SoC die. See "A 1 V Wireless Transceiver for an Ultra-Low-Power SoC for Biotelemetry Applications," IEEE Journal of Solid-State Circuits, July 2008, p. 1511.

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