Continuous Class F−1 Ku Band GaN MMIC Power Amplifier With an Effect of Nonlinear Output Capacitance

This brief presents the design of a Ku band GaN MMIC power amplifier (PA) using UMS $0.25~\mu \text{m}$ GaN MMIC technology. The Nonlinear output capacitance $(C_{out})$ of the GaN HEMT is used to improve the efficiency of the PA. The design equations of the continuous class F−1 (CCF−1) mode are redefined to present active second harmonic loads. It is noted that the efficiency of PA improves with active second harmonic loads compared to conventional CCF−1 mode, where loads are purely reactive. In CCF−1 mode with active second harmonic load, the peak of the current waveform increases to show half-sinusoidal characteristics and improves the output power and efficiency of the PA. An analysis is presented to investigate the impact of nonlinear $C_{out}$ on the performance of the GaN MMIC PA. The nonlinear $C_{out}$ can present an active second harmonic load at the current source reference plane (CRP), even with a passive matching network at the extrinsic reference plane (ERP). The proposed theory is validated by designing a PA operating from 16.5 to 17.4 GHz. The chip size of the two-stage GaN MMIC PA is 3mm $\times 5$ mm. The Ku band GaN MMIC PA has achieved the power-added efficiency (PAE) of 15.7 to 26% with an output power of 36.7 to 38.9 dBm. The gain at saturation varied from 9.7-14.3 dB. The input and output reflection coefficients of the implemented PA are less than −6.5 dB and −10 dB, respectively.