A Digital Predistortion Power Amplifier for the NB-IoT Standard

Purpose and goal

A power-amplifier with digital pre-distortion (DPD) that meets the power, bandwidth, linearity, and efficiency requirements of NB-IoT transmitters, is demonstrated in a 22nm FD-SOI process. Measurements confirm that the PA covers the entire frequency band for NB-IoT and LTE-M standards. The DPD and SRAM, can be operated energy efficiently at an aggressively scaled supply voltage. Several innovative techniques are applied to exceed the RF and digital performance currently offered in state-of-the-art.

Expected results and effects

We will finalize the remaining measurements of the PA in the near future and publish the results at prestigious conferences and journals. The future plan is the integration of the whole transmitter chain including, DPD and memory into a single chip. This single-chip solution will demonstrate that a single-stage PA solution is feasible for two different communication standards, where the different bands can be configurable in the time domain. Xenergic has already promoted the SRAM at technology events, and will consider other CMOS technologies for low-voltage SRAM during 2022.

Planned approach and implementation

The PA and DPD were designed at Lund university (department of EIT), and the SRAM was designed at Xenergic and fabricated though the companies´ own supply channels. EIT had to back-up an initial recruitment with a more experienced researcher, which turned out to be a success. The duties of Xenergic were distributed among the team, and the main focus was the integration of the technology and low-power architecture in Xenergic´s in-house developed compiler (MemoryTailor). Silicon measurements were conducted simultaneously using facilities at EIT and Xenergic.