A 7–13-GHz Broadband High-Efficiency MMIC Power Amplifier Using Second Harmonic Inductively Tuning Network

This letter presents a three-stage 7–13-GHz broadband high-efficiency monolithic microwave integrated circuit (MMIC) power amplifier (PA) implemented in a commercial 0.25-<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m GaAs pHEMT process. A novel second harmonic tuning method based on the RC model of the transistor is proposed for the efficiency maximization in a broadband range. In the output matching network (MNO), an inductive tuning network (ITN) is adopted to resonate with the parasitic capacitance seen from the intrinsic drain plane. With this method, the second harmonic is effectively tuned to an open-circuit state, which minimizes the overlaps of the drain current and voltage waveforms, thus greatly improving the efficiency. To achieve a broadband performance, a low-pass matching structure (LPMS) is employed to shift the matching trajectory of the fundamental impedance to nearby <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$50~\Omega $ </tex-math></inline-formula> by compensating the reactance of the fundamental impedance with negligible effect on the tuning of the second harmonic. Over the frequency range of 7–13 GHz, the MMIC PA delivers a saturated output power (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$P_{\text {SAT}}$ </tex-math></inline-formula>) of 35.0–36.5 dBm with a power-added efficiency (PAE) of 42%–47.4% in the continuous wave (CW) mode and a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {SAT}}$ </tex-math></inline-formula> of 35.5–36.9 dBm with a PAE of 43.8%–49.6% in the pulse mode.