A Large Dynamic Range Reconfigurable Interpolation Digital Transmitter for NB-IoT Applications

In this paper, we present a digital transmitter for dual-band NB-IoT applications achieving a large dynamic range with high speed Cartesian RF-DACs requiring less area and consuming low power consumption. The proposed transmitter incorporates integrated output baluns, a reconfigurable digital interpolater based oversampling for DAC image suppression or avoidance of coexistence channel. A true SAW-less design is realized by external low-cost low-pass filtering of the spurious emission satisfying NB-IoT requirements. Implemented in standard 40nm CMOS technology with a core area of 1.15x1.3 mm2 and packaged with QFN-68, the transmitter achieves a dynamic range of -47.5 to 24.8 dBm with EVM < -25 dB. The peak efficiency is 44.1% at 28.7 dBm output power, with a 2.4 V power supply.