Load Modulated Balanced mm-Wave CMOS PA with Integrated Linearity Enhancement for 5G Applications

The paper presents an mm-Wave load modulated balanced amplifier (LMBA) architecture across 30–40 GHz. The architecture is implemented with a transformer-based hybrid at input and output to allow wideband power combining and achieve high isolation with a control PA for load-modulation and back-off efficiency enhancement across 30–40 GHz. To overcome the compressive behaviour of an LMBA and enhance linearity, an integrated adaptive biasing is integrated on-chip allowing superior ACLR performance across 30–40 GHz. Under CW excitation, the two-stage LMBA demonstrates output power of 18.5–20 dBm, output drain efficiency >30% across 30–40 GHz. The modulation capabilities of LMBA are tested using a 64 QAM signal with a data rate of 6 Gbps wherein PA demonstrates EVM of -26.4 dB and ACLR of -29 dBc at an average output power of 10.6 dBm. To the best of the authors’ knowledge, this is the first load-modulated balanced PA at mmWave in silicon.