Fully digital polar transmitter for IoT applications

08 February 2016

Imec and Holst Centre present Wi-Fi HaLow low-power fully digital polar transmitter for IoT applications.

At the IEEE International Solid-State Circuits Conference (ISSCC 2016), Imec and Holst Centre presented a 1.3nJ/b fully digital polar transmitter optimised for IoT applications and the novel IEEE 802.11ah Wi-Fi protocol, with a ten-fold power reduction as compared to OFDM transmitters. 

At the Consumer Electronics Show (CES 2016) in January 2016, the Wi-Fi Alliance introduced the HaLow (TM) designation for the new low power, long range Wi-Fi protocol IEEE802.11ah, developed by the IEEE standardisation committee. This new protocol is especially optimised for Internet-of-Things applications. Compared to other IoT standards, its sub-GHz carrier frequency and mandatory modes with 1MHz/2MHz channel bandwidths allow devices to operate in a longer range with scalable data rates from 150kb/s to 2.1Mb/s. The standard uses OFDM to improve the link robustness against fading, which is important in urban environments, and to achieve a high spectral efficiency (data rate over a given bandwidth).

Imec and Holst Centre’s fully-digital polar transmitter meets the tight spectral mask and error-vector-magnitude (EVM) requirements of conventional Wi-Fi standards. The measured phase noise at 1.5MHz offset is -115dBc/Hz which is 15dB lower than the spectral mask requirement for the IEEE 802.11ah standard. At 1MHz/2MHz with 64-QAM OFDM data packets, both the far-out and close-in spectrum pass the mask with at least 4.8dB margin. The EVM is below 4.4%. The power consumption of the transmitter is as low as 7.1mW, when delivering 0dBm output power and operating from a 1V supply. This represents a 10x power reduction compared to OFDM transceivers, and consequently, the prototype transmitter chip meets the stringent requirements for IoT applications. 

Imec’s internet-of-things R&D program aims at developing the building blocks for the future internet-of-things, an intuitive IoT, with sensor systems that are aware of us, our perspective and our environment and react exactly as we need or want, assisting us in an unobtrusive way. Imec’s research activities focus on the development of ultra-small, low-cost, intelligent, and ultra–low power sensors, radio chips and heterogeneous sensor networks. Interested companies are invited to join the research efforts as research partner or they can have access to the technology for further development through licensing programs.

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