This letter presents a simple approach to design ultrabroadband power amplifiers (PAs). The theories of the hybrid modes class-EFJ PAs are applied. The relationship between the operating frequency and load impedance is analyzed for class-EFJ PAs. By appropriately selecting load impedances at different frequencies, a PA can work well in 1.0-4.0 GHz with high efficiency. In addition, the second harmonic impedance is obtained by combining the selected fundamental impedance and load-pull simulation. For validation, an ultra-broadband high efficiency PA is implemented. Experiments show that output power is from 40.1 dBm to 42.6 dBm and drain efficiency is between 60.6% and 72.7% at the saturation level in 1.0-4.0 GHz. The ACLR is smaller than -27.2 dBc in the same frequency band with an average output power of 35.2 dBm.
A novel 7.2 dB output power back off Doherty power amplifier (DPA) based on asymmetrical load is proposed using two same transistors in this paper. To get maximum efficiency at back-off output power and the largest saturate output power level simultaneously, the carrier power amplifier (PA) is matched to the maximum efficiency region when peaking PA is almost off, and both of the two PAs are matched to maximum power region to get largest output power. According to the proposed design methodology, high efficiency at back-off power and high peak power DPA is designed and fabricated with two Cree's GaN HEMT CGH40010F devices. Measurements results show that the saturated output power of the DPA is over 44.5 dBm, the drain efficiency when 7.2 dB output power back off and saturate power are above 42% and 53%, respectively, in the range of 3.4-3.8 GHz. Meanwhile, better than −47.8 dBc adjacent channel leak power ratio can be achieved with digital predistortion under 20 MHz LTE signal testing at 3.4 GHz, the final design size is only 14 × 12 cm 2 .
K E Y W O R D Sdigital predistortion, Doherty power amplifier, GaN HEMT, peak-to-average power ratio
This paper presents impact of layout sizes of Al0.27Ga0.73N/AlN/Al0.04Ga0.96N/GaN HEMT heterostructure high-mobility transistors (HEMTs) on SiC substrate on its characteristics that include the threshold voltage, the maximum transconductance, characteristic frequency, and the maximum oscillation frequency. The changing parameters include the gate finger number, the gate width per finger. The measurement results based on common-source devices demonstrate that the above parameters have different effects on the threshold voltage, maximum transconductance, and frequency characteristics.
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