A High-Efficiency E-band Power Amplifier with Optimized Output Matching Network in a 28-nm Bulk CMOS

This paper presents an E-band high-efficiency power amplifier (PA) implemented in a 28-nm bulk CMOS technology. The output matching network (OMN) is optimized for high power and high efficiency through a co-optimization technique where the optimum load admittance (Yopt) is derived by incorporating the loss of the OMN with the active device performance. In the mm-wave band, a transformer with a single turn ratio is widely used for OMN but poses a limitation on the maximum achievable conductance (Gout.max) to be seen by the output transistor. Therefore, a shunt capacitor (CL) is employed in this work to boost Gout.max up to the value required for reaching Yopt. Finally, the transformer dimension and CL are optimized for high efficiency and power through the co-optimization technique. The measurement shows that the PA exhibits more than 13.4 dBm of saturated power from 65 to 80 GHz. A peak power-added efficiency (PAE) of 27 % is achieved at 71 GHz, which is the highest PAE among the reported E-band CMOS PAs to the best of authors' knowledge. The PAE is maintained higher than 20 % from 65 to 75 GHz. The PA exhibits a rms EVM of -25.8 dB, average PAE of 8.7 %, and average output power of 5.8 dBm with a 3-Gbps 64-QAM signal.