A Ku-Band CMOS Two-Way In-Phase Power Combining Amplifier with 26.3-dBm P_sat and 1.1° AM-PM Distortion

This letter presents a Ku-band power combining amplifier (PCA) using the 65-nm CMOS process. Because of the large size of the pi-network used in Wilkinson combiners, a transformer (TF)-based series combining method was employed to achieve a more compact design, reducing insertion loss and maximizing the power amplifier (PA)'s performance. A parallel combining topology enables a symmetric TF design, whereas a series combining topology inherently results in an asymmetric structure, leading to unavoidable phase and gain imbalance between two signals. To mitigate this issue, we propose an asymmetric in-phase TF-based power combiner that minimizes phase imbalance between two PAs and to improve output power and efficiency. The designed PA demonstrates a saturation output power (P) of 26.3 dBm, peak power-added efficiency (PAE) of 30.3%, and P_1dB of 25 dBm at 16 GHz. Also, the phase imbalance between the two power stages to the output was improved from 15° to 2°. The proposed PA delivers a linear output power of 19.5 dBm under a 5G NR FR2 100-MHz 64-QAM signal, demonstrating its suitability for high-linearity applications.