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An ultra-low-power sensor interface built around a reconfigurable incremental sigma-delta modulator for sensor networks employing electromagnetic backscatter

: Gay, N.; Fu, Q.; Hildebrandt, R.; Bansleben, C.; Heiss, M.; Fischer, W.-J.


Institute of Electrical and Electronics Engineers -IEEE-:
IEEE Asia Pacific Conference on Circuits and Systems, APCCAS 2008. Vol.1 : Macao, China, 30 November - 3 December 2008
New York, NY: IEEE, 2008
ISBN: 978-1-4244-2341-5
ISBN: 978-1-4244-2342-2
Asia Pacific Conference on Circuits and Systems (APCCAS) <9, 2008, Macao>
Fraunhofer IPMS ()

An ultra-low-power four-channel sensor interface for wireless sensor networks employing semi-active RFID transponders as sensor nodes is described in the present paper. Each channel is based on a self-contained switched-capacitor second-order single-bit Sigma Delta-modulator operated in an incremental manner. The power consumption can be regulated through variation of the sampling frequency (max. 1MHz), signal bandwidth (8Hz-16kHz), output resolution (max. 16 bits) and/or output word rate. The input and output stages of the employed amplifiers are both class AB for a high energy efficiency. Moreover, the bias current of every amplifier can be programmed according to the actual power availability, thus dynamically exchanging DC-gain, gain-bandwidth-product and slew-rate against power consumption. In addition, two channels may be cascaded (2-2 MASH configuration), further incrementing the resolution and/or reducing the number of clock cycles to obtain a given resolution. The MASH configuration uses an on-line adaptive noise cancellation scheme to further enhance the noise-shaping characteristic of the converter. The power consumption per channel ranges from 4 to 20 mu W at a supply voltage of 1.4V