This paper examines system and circuit design techniques for a micro-Watt node operating at a power level low enough to enable the use of an energy scavenging source. Despite several architectures have been investigated in order to reduce the overall system power consumption, none of them is able to guarantee robustness of the link and ultra-low power consumption at the same time. A survey of the most advanced architectures meant for ultra-low power transceivers is described. Advantages and drawbacks of all these systems are discussed and the reasons for an architecture based on Frequency-Hopping (FH) Spread-Spectrum (SS) are discussed. Finally a novel FH synthesizer based on a digital pre-distortion architecture is proposed in order to reduce the power consumption of the hopping synthesizer. The FH architecture together with a frequency offset robust demodulation technique allows a reduction by a factor 8 of the power consumption compared to the state-of-the-art synthesizers. Furthermore, a single RF block front-end is obtained combining the VCO and the PA. The novel RF front-end can be directly coupled to the antenna through a balun and the system is able to deliver -18 dBm output power on a 50 Ω load at 1 mA current consumption (2 V power supply). To prove the new synthesizer principle a communication link in the 902-928 MHz ISM band has been set-up. The receiver, mainly software with a flexible RF frontend, adopted a ST-DFT demodulation algorithm and achieved a BER smaller than 1.1% at -25 dBm output power, with TX and RX antennas placed at 8 meters distance in a NLOS condition and in a common office environment.
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- ULTRA-LOW POWER FREQUENCY-HOPPING SPREAD SPECTRUM TRANSMITTERS AND RECEIVERS
Johan van der Tang
Arthur H.M. Van Roermund
- Springer Netherlands