A Compact 24-30GHz Doherty Power Amplifier with a Flexible T-Type L-C-L Series Combiner and New Power Sensing Method for 5G Communications

This paper presents a series Doherty power amplifier (PA) fabricated in 40nm CMOS for fifth-generation (5G) millimeter-wave (mm-Wave) communications. A novel series Doherty combiner is synthesized by lumped T-type L-C-L elements, which models the interconnection more accurately and provides better agreement between behavioral and electromagnetic (EM) simulations. A new power sensing method is proposed by extracting the interstage voltage of the typical adaptive bias circuit (ABC). This PA is implemented in a compact layout with a core size of 0.22mm ² . The measured 3-dB small-signal bandwidth is 23.0-31.1GHz. The PA achieves a peak $\mathbf{P}_{\text{sat}}/\mathbf{P}_{1\mathrm{d}\mathrm{B}}$ of 18.0/17.4dBm, while the peak $\text{PAE}_{1\mathrm{d}\mathrm{w}}$ and $\mathbf{PAE}_{\text{sat}-6\mathrm{d}\mathrm{B}\}}$ are 29.4% and 24.5%, respectively. The PA has been tested with a 64-QAM 100MSym/s modulated signal at 27GHz and achieves $\mathbf{P}_{\text{avg}}, \text{PAE}_{\text{avg}}$ of 9.1dBm/16.9 ^% while $\text{EVM}_{\text{RMS}}$ and ACPR is −24.4/−25.7dBc. The 16-QAM 500MSym/s signal has also been tested at 27GHz and the PA obtains P avg , $\text{PAE}_{\mathrm{a}\mathrm{v}\mathrm{g}}$ of 7.1dBm/13.0% while $\text{EVM}_{\mathrm{R}\mathrm{M}}\mathrm{s}/\text{ACPR}$ is −20.9dB/−21.7dBc.