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The aim of this paper is to improve the linearity of an envelope tracking (ET) power amplifier (PA) using a simple baseband linearisation approach (BLA), which releases the requirement for the ET-customised digital predistortion (DPD) techniques. The proposed BLA is verified through the comparative study on a Gallium Nitride (GaN) PA with ET and a 28V supply voltage. A two-tone signal and a 20MHz modulated signal are used in the measurement, which demonstrates that in contrast to the 28 V case, the ET PA using BLA can simultaneously achieve higher efficiency and better linearity. To investigate the linearity improvement of using BLA, the constellation diagrams, AM/AM and AM/PM characteristics with and without generalized memory polynomial (GMP)-based DPD are measured and analysed.

This paper presents a novel technique for the design of broadband Doherty power amplifiers (DPAs), supported by a simplified approach for the initial bandwidth estimation that requires linear simulations only. The equivalent impedance of the Doherty inverter is determined by the value of the output capacitance of the power device, and the Doherty combiner is designed following this initial choice and using a microstrip network. A GaN-based single-input DPA designed adopting this method exhibits, on a state-of-the-art bandwidth of 87% (1.5–3.8 GHz), a measured output power of around 20 W with 6 dB back-off efficiency between 33% and 55%, with a gain higher than 10 dB. System-level measurements prove the linearizability of the designed Doherty amplifier when a modulated signal is applied.

This letter presents an integrated Doherty power amplifier (PA) in 0.25- $\mu \text{m}$ GaN on SiC process. Designed for 15-GHz point-to-point radios, the PA exhibits an output power of 36 ± 0.5 dBm between 13.7 and 15.3 GHz, while at 14.6 GHz, it shows a 6-dB output back-off efficiency higher than 28%. Modulated signal measurements applying digital predistortion demonstrate the compatibility of the amplifier with point-to-point radio requirements. To the best of our knowledge, this PA has the highest back-off efficiency for the 15-GHz band, and is the first GaN Doherty in the Ku-band.

This letter presents the design strategy for an ultra-wideband, high-efficiency hybrid power amplifier based on a commercial GaN-HEMT. The measurement results demonstrate a state-of-the-art fractional bandwidth of 145.5%, with saturated output power higher than 10 W from 0.6 to 3.8 GHz and power added efficiency exceeding 46% in the whole band, thus covering most of the mobile frequencies and making this device suitable for small-base station applications. The simple design approach exploits a $N$ -section transformer, and allows for a priori estimation of the bandwidth: in the proposed case, a good agreement between estimated and measured bandwidth is obtained.

This paper presents the design of two combined linear power amplifiers for 7-GHz microwave backhaul, realized in 0.25- μm GaN on SiC monolithic technology. Both modules are based on a combined class-AB structure conceived for maximum back-off efficiency and reduced phase distortion, which are important requirements in backhaul systems. Different second harmonic loads are exploited in the two power amplifiers, leading to different performance in terms of output power, bandwidth and efficiency. The two stages exhibit a saturated output power in excess of 35 and 36 dBm on 16% and 26% of fractional bandwidth, respectively; moreover, the measured average efficiency in the presence of modulated signals with 7.4-dB peak-to-average power ratio is 18% and 25%. Simulations and experimental results demonstrate that the second-harmonic load has little influence on the linearity of the proposed amplifiers. Compliance with the spectrum emission mask defined for the targeted application has been achieved through low-order polynomial digital predistortion, thus demonstrating the high linearity of the stages. A comparison with a Doherty amplifier realized in the same technology and for the same application shows that the two proposed stages need a simpler predistorter to achieve the linearity required by standard specifications.

Este artículo presenta una discusión sobre las estrategias de diseño de diferentes tipos de amplificadores de potencia para aplicaciones RF/Microondas, tales como el amplificador de carga sintonizada, Clase F, F inverso y Doherty. Además, se muestra la caracterización en onda continua de los amplificadores arriba mencionados, y una comparación de los resultados obtenidos, en términos de ganancia, eficiencia y potencia de salida.

Este artículo presenta el concepto general del amplificador de potencia Doherty, resaltando su superioridad, en términos de eficiencia promedio, con respecto a amplificadores de una etapa. Además, se presenta la posibilidad de incluir etapas de pre-amplificación en las ramas del amplificador Doherty, con el objetivo de incrementar su ganancia.