Architecture for ultra-low power multi-channel transmitters for Body Area Networks using RF resonators

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 99-103).Body Area Networks (BANs) are gaining prominence for their use in medical and sports monitoring. This thesis develops the specifications of a ultra-low power 2.4GHz transmitter for use in a Body Area Networks, taking advantage of the asymmetric energy constraints on the sensor node and the basestation. The specifications include low transmit output powers, around -10dBm, low startup time, simple modulation schemes of OOK, FSK and BPSK and high datarates of 1Mbps. An architecture that is suited for the unique requirements of transmitters in these BANs is developed. RF Resonators, and in particular Film Bulk Acoustic Wave Resonators (FBARs) are explored as carrier frequency generators since they provide stable frequencies without the need for PLLs. The frequency of oscillation is directly modulated to generate FSK. Since these oscillators have low tuning range, the architecture uses multiple resonators to define the center frequencies of the multiple channels. A scalable scheme that uses a resonant buffer is developed to multiplex the oscillators' outputs to the Power Amplifier (PA). The buffer is also capable of generating BPSK signals. Finally a PA optimized for efficiently delivering the low output powers required in BANs is developed. A tunable matching network in the PA also enables pulse-shaping for spectrally efficient modulation. A prototype transmitter supporting 3 FBAR-oscillator channels in the 2.4GHz ISM band was designed in a 65nm CMOS process. It operates from a 0.7V supply for the RF portion and 1V for the digital section. The transmitter achieves 1Mbps FSK, up to 10Mbps for OOK and BPSK without pulse shaping and 1Mbps for OOK and BPSK with pulse shaping. The power amplifier has an efficiency of up to 43% and outputs between -15dBm and -7.5dBm onto a 50Q antenna. Overall, the transmitter achieves an efficiency of upto 26% and energy per bit of 483pJ/bit at 1Mbps.by Arun Paidimarri.S.M

Energy-Efficient Wake-up Receivers for 915-MHz ISM Band Applications

Wake-up receiver (WuRx) is a well-known approach for optimizing the latency and power consumption of ultra-low power transceivers in wireless sensor nodes. Tuned RF (TRF) or Envelope Detection architecture is an appropriate topology for short-range Wireless Body Area Network (WBAN) applications, where achieving a very high sensitivity is not a priority. However, the demand for an improved sensitivity gets emphasized for longer transmission ranges. Regardless of the application, considering the existing trade-off between the power and sensitivity, design techniques and novel architectures are usually employed to optimize the power-sensitivity product. Moreover, considering the negative impact of higher data rate on the sensitivity, the energy-sensitivity product can be a more reasonable figure of merit when comparing WuRx designs. In this thesis, the RF-subsampling architecture has been combined with the TRF receiver architecture as a first approach for improving the power-sensitivity product. The overall power consumption is reduced as a result of employing the subsampling topology with a low-frequency local oscillator (LO). Post layout simulations show that the proposed WuRx draws only 56 μA from a 0.5 V supply and exhibits an input sensitivity of -70 dBm for a data rate of 100 kbps. The chip occupies an area of 0.15 mm2 and is fabricated with TSMC 90nm CMOS technology. Another major contribution of this work is to propose and implement a novel dual-mode ultra-low-power WuRx based on the subsampling topology, which not only reduces the overall power consumption but also optimizes the energy-sensitivity product of the receiver. During the typical mode of operation known as the Monitoring (MO) mode, the start frame bits are received at a rate of as low as 10 kbps. Having received the true preamble bits in the MO mode, the remaining wake-up pattern bits are received at a higher rate of 200 kbps during the Identifier (ID) mode. By lowering the gain of the front-end amplifier in the MO mode, the power dissipation is reduced, which in turn causes an increase in the overall noise figure of the receiver. However, adequate sensitivity and hence an optimized energy-sensitivity product is maintained by intentionally lowering the data rate as well as the detection bandwidth of the receiver in the MO mode. The proposed wake-up receiver has been designed and fabricated in IBM 130 nm technology with a core size of about 0.2 mm2 for the target frequency range of 902-928 MHz. The measured results show that the proposed dual-mode receiver achieves a sensitivity of -78.5 dBm and -75 dBm while dissipating an average power of 16.4 µW and 22.9 µW during MO and ID modes, respectively

A low power, reconfigurable fabric body area network for healthcare applications

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 105-110).Body Area Networks (BANs) are gaining prominence for their capability to revolutionize medical monitoring, diagnosis and treatment. This thesis describes a BAN that uses conductive fabrics (e-textiles) worn by the user to act as a power distribution and data communication network to sensors on the user's body. The network is controlled by a central hub in the form of a Base Station, which can either be a standalone device or can be embedded inside one of the user's portable electronic devices like a cellphone. Specifications for a Physical (PHY) layer and a Medium Access Control (MAC) layer have been developed that make use of the asymmetric energy budgets between the base station and sensor nodes in the network. The PHY layer has been designed to be suitable for the unique needs of such a BAN, namely easy reconfigurability, fault-tolerance and efficient energy and data transfer at low power levels. This is achieved by a mechanism for dividing the network into groups of sensors. The co-designed MAC layer is capable of supporting a wide variety of sensors with different data rate and network access requirements, ranging from EEG monitors to temperature sensors. Circuits have been designed at both ends of the network to transmit, receive and store power and data in appropriate frequency bands. Digital circuits have been designed to implement the MAC protocols. The base station and sensor nodes have been implemented in standard 180nm 1P6M CMOS process, and occupy an area 4.8mm2 and 3.6mm2 respectively. The base station has a minimum power consumption of 2.86mW, which includes the power transmitter, modulation and demodulation circuitry. The sensor nodes can recover up to 33.6paW power to supply to the biomedical signal acquisition circuitry with peak transfer efficiency of 1.2%.by Nachiket Venkappayya Desai.S.M

SiGe-based broadband and high suppression frequency doubler ICs for wireless communications

制度:新 ; 報告番号:甲3419号 ; 学位の種類:博士(工学) ; 授与年月日:2011/9/15 ; 早大学位記番号:新574