Broadband Saturated Power Amplifier With Harmonic Control Circuits

This letter presents a broadband saturated power amplifier (PA) using the harmonic control circuits for base station application. The saturated PA has advantages for broadband operation with high efficiency due to the large tolerance of the second harmonic tuning. However, it is difficult to simultaneously achieve the fundamental and second harmonic impedance matching across a wide bandwidth. To solve the problem, the harmonic control circuits are placed at the input and output of the device's die. These harmonic control circuits play a role of leading the second harmonic impedances to the optimum regions but are specially designed to be insensitive to the following fundamental matching circuit. The saturated PA with the harmonic control circuit is designed using a 120 W GaN device, achieving a high efficiency and wide bandwidth characteristics simultaneously. The measured output power, drain efficiency, and gain are at least 51.0 dBm, 71.0%, and 8.22 dB at the saturation across the 1.75 to 2.17 GHz (21% relative bandwidth) under pulse test (10% duty). This saturated PA also delivers good performances for long term evolution (LTE) and wideband code division multiple access (WCDMA) modulated signals at 1.85 and 2.14 GHz, respectively. These results show that the broadband saturated PA with the harmonic control circuit is suitable to wide bandwidth multimode/multiband applications.