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Title: Energy Aware RF Transceiver for Wireless Body Area Networks (WBAN)
Keywords: OOK Transceiver, low power radio, rise time of oscillator, SRR, SRO, quench alignment
Issue Date: 31-Oct-2011
Source: MUTHUSAMY KUMARASAMY RAJA (2011-10-31). Energy Aware RF Transceiver for Wireless Body Area Networks (WBAN). ScholarBank@NUS Repository.
Abstract: Transceivers for wireless body area networks (WBAN) are expected to consume low power for long battery life or to operate from other limited power supplies such as solar cells. Hence, the transceivers are typically bench marked by the energy consumed in transmitting a bit and is measured in nJ/bit. In addition, features which reduces the overhead power consumption and increase the effective throughput per energy consumed, such as duty cycling and variable data rate that adapts to the payload, are employed. A transceiver for WBAN, which makes use of ON-OFF Keying (OOK) modulation scheme, is proposed. The proposed transmitter circuit completely turns off the transmitter during the transmission of ¿0¿ and employs speed up schemes to support larger data rates and faster wake up and sleep times. A closed form equation is derived to find the start up time of a colpitts oscillator, and a speed up circuitry based on the equation is demonstrated. The buffer also employs speed up circuitry for the signal build up and decay. This leads to a data rate increase from 3 Mb/s to 10 Mb/s without any penalty on power consumption. The data rate can also be made adaptable by varying the duration in which the bias current is increased. The proposed OOK transmitter is implemented in a 0.35-µm CMOS technology. The measured results show that the transmitter achieves a maximum data rate of 10-Mb/s with a dc power consumption of 518 µW under a 1-V power supply, yielding an energy efficiency of 52 pJ/bit or 0.97 nJ/[bit×mW], when normalized to the output power. Super regenerative receiver (SRR) architecture is used in the receiver, since the super regenerative oscillator (SRO) provides a large RF gain, while consuming vi least current. The sensitivity of the SRR depends upon the quench frequency and the quench frequency is normally few times the data rate for oversampling purpose. However, the oversampling ratio limits the sensitivity. In order to alleviate this issue the proposed SRR uses the minimum quench frequency which is equal to the data rate and recovers the correct phase of the incoming data by gradually incrementing the quench phase until the recovered data matches a predetermined pattern. Measured Results of the SRR, shows a data rate of 5 Mb/s to 10 Mb/s, with sensitivity from -61 dBm to -53 dBm respectively. The power consumption is only 665 µW, achieving an energy efficiency of 133 pJ/bit. Finally the proposed transceiver shares the same colpitts oscillator for both carrier generation in the transmitter and SRO in the receiver saving the silicon area. Such reduction of area assumes importance in implanted applications. The transmitter and receiver maintain an energy efficiency of 52 pJ/bit and 133 pJ/bit respectively. The performance is favorable when compared with the state of the art, in spite of using a cost effective 0.35-µm CMOS technology.
Appears in Collections:Ph.D Theses (Open)

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