An Optimal Dual-Band Output Matching Method for a Power Amplifier

Abstract

This article presents an optimal dual-band output matching method for a power amplifier (PA). The proposed matching method utilizes series and parallel resonance to transform a frequency-dependent optimum load impedance of a transistor to 50 Ω at target frequencies. The selectable range of a low-frequency is analyzed when a high-frequency is selected. A 2.45-/5.8-GHz PA was designed and fabricated on the Rogers 5880 substrate, utilizing the Wolfspeed gallium nitride (GaN) high electron mobility transistor (HEMT) of CGH40006s. The PA achieves a small signal gain ( S21) of 13.9 dB at 2.45 GHz and 10.5 dB at 5.8 GHz. At the 3-dB compression point, the output power (OP 3dB) is measured at 38.4 dBm for 2.45 GHz and 38.6 dBm for 5.8 GHz, while the corresponding drain efficiency (DE 3dB) is 71% at 2.45 GHz and 59.7% at 5.8 GHz. Furthermore, to verify the effectiveness of the matching method in the millimeter-wave region, a 28-/48-GHz PA was implemented using a 0.15- μ m gallium arsenide (GaAs) pseudomorphic HEMT (pHEMT). The PA has S21 of 22.6 dB at 28 GHz and 15.5 dB at 48 GHz. The OP 3dB was 19.1 dBm at 28 GHz and 18.6 dBm at 48 GHz, with the power-added efficiency (PAE 3dB) corresponding to 37.3% and 28.5%.