C-Ku band 120% relative bandwidth high efficiency high power amplifier using GaN HEMT

This paper reports on a GaN HEMT (gallium nitride high electron mobility transistor) HIC (hybrid integrated circuit) high power amplifier, which features high efficiency over C-Ku band 120% relative bandwidth. It was found that the output impedance of a transistor under high efficiency operation can be modeled by parallel circuit of R and C. In the circuit design, BPF (band pass filter) configuration is employed, where parasitic capacitance of the transistor is utilized as a part of BPF matching circuit. Hence broadband matching was successfully obtained. A C-Ku band GaN HEMT HIC amplifier was manufactured and measured at 30 V drain voltage. More than 4 W output power and 18% PAE (Power Added Efficiency) were obtained over 120% relative bandwidth. This result is state-of-the-art high efficiency for GaN HEMT HIC amplifier with more than 100% relative bandwidth.

I. Introduction

Recently, many GaN HEMT (Gallium Nitride High Electron Mobility Transistor) broadband amplifiers have been reported [1]–[4], [9]–[12]. GaN HEMT seems to be attractive for high power and high efficiency broadband amplifiers, considering those characteristics of GaN HEMT such as high drain voltage and high power density. High drain voltage results in small impedance transformation ratio. Moreover high power density reduces size of gate periphery. Hence GaN HEMT is suitable for broadband amplifiers.