A 15-W <i>X</i>-Band Inverse Class-F GaN Power Amplifier With Second-Harmonic Input Tuning
Ahmad Ghanaatian, Adib Abrishamifar, Abdolreza Rahmati, Amirreza Alizadeh
Abstract
This letter presents an inverse class-F power amplifier (PA) where the second-harmonic voltage produced by the nonlinear gate–source capacitor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$C_{\text {GS}}$ </tex-math></inline-formula> ) of the gallium nitride (GaN) HEMT transistor improves the PAE and output power. The design is based on multiharmonic recursive source-pull (SP) and load-pull (LP) simulations to determine the optimum design space. With proper impedance terminations at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{{0}}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${2}f_{{0}}$ </tex-math></inline-formula> , the second-harmonic input voltage improves the PAE by about 10%. An <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X}$ </tex-math></inline-formula> -band proof-of-concept PA is implemented in a 250-nm GaN technology with a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\text {max}}$ </tex-math></inline-formula> of 50 GHz. At 9.5-GHz center frequency, 17.8 W peak output power and 43% power added efficiency are achieved for pulsed-mode operation with a pulse repetition frequency of 10 kHz and a duty cycle of 10%. The designed three-stage PA consumes 7.72 mm2 die area and dissipates about 39 W dc power at saturation.