A 2.4-GHz BAW-Based Transceiver for Wireless Body Area Networks

Abstract

This paper presents a BAW-based transceiver targeting wireless networks for biomedical applications. The use of high-Q microelectromechanical-systems resonators brings interesting benefits to the fundamental building blocks of the frequency synthesis, receiver, and transmitter and allows achieving at the same time low-power consumption, improved phase noise, and high selectivity in the receiver and transmitter paths. In the baseband, the power consumption is minimized thanks to the use of a phase analog-to-digital converter (ADC) which directly quantizes the phase of the received signal instead of using two separate amplitude ADCs. A complete wireless node composed of the transceiver integrated circuit (IC) and a microprocessing IC, both integrated in a standard digital 0.18-μm complementary metal-oxide semiconductor technology are described and validated by measurement results. The RF carrier phase noise is -136.2 dBc/Hz at 1-MHz offset. The transmitter demonstrates 1-Mb/s Gaussian frequency-shift keying modulation at an output power of 5.4 dBm with an overall current of 35 mA, in compliance with Bluetooth and Bluetooth low energy output spectrum requirements. At the receiver, further investigations are needed to find the origins of an unexpected sensitivity of -75 dBm at 200 kb/s.

A Comparative Analysis of Phase-Domain ADC and Amplitude-Domain IQ ADC

“…This is one of fundamental benefits of the PhADC over the IQ ADC. This benefit has also been proven by measurement results in [6], [7], [10] and summarized in [10] by the authors.…”

“…As shown by the upper curve in Fig. 3(a), linearly increases with , which can be fitted to a linear function as: (6) The SNR of an amplitude ADC is usually quantified by a more intuitive metric, i.e., effective number of bits (ENOB) according to:…”

“…A rotated projection is related to the fundamental projections and as follows [4], [7]: (11) This linear combination function can be implemented in circuitry either by a resistive bridge that converts input currents to phase-shifted voltages [5], [6], or a weighted current array that converts input voltages to phase-shifted currents [7].…”

“…Manuscript PhADC-based demodulators have proven to have bit-error-rate (BER) characteristics close to an ideal coherent GFSK demodulator [4]. PhADCs based on a zero-crossing conversion algorithm have been realized in silicon by a resistor-bridge-based approach [5], [6] as well as a current-mirror-based approach [7], [8]. The benefits of robustness to circuit nonidealities and noise and large amplitude dynamic range of the resistor-bridge-based zero-crossing (ZC) PhADC has been addressed in [9].…”

Addressing the Need for Context Awareness and Security Requirements in Wireless Body Area Networks

“…Context is defined as any information that can be used to characterize the situation of an entity, where an entity can be a person, place or physical object [14].This kind of technique is used to detect the internal or external state of a user. Context-aware computing describes the situation of a wearable or mobile computer being aware of the user's state and surroundings, and modifying its behavior based on this information [15].Context-awareness plays an important role in body area networks because it interprets various physical and biochemical signals coming from body sensor networks by considering the present state of the user and the state of the environment.…”