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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.

This letter presents the design approach for a compact, single-stage, wideband MMIC power amplifier. A method is proposed to compensate for the output capacitance of the active device over a frequency range as wide as possible, with minimum impact on the achievable output power, which leads to a two-element compensating network. A three-section transformer is then adopted for a real-to-real transformation. The CW characterization shows the output power higher than 32 dBm and the drain efficiency between 35% and 45%, over a fractional bandwidth of 148%, from 3 to 20 GHz.

This paper presents a novel approach to incorporate gate bias voltage variations into the Cardiff behavioural model formulation. In particular, it is observed that the model coefficients can be expressed effectively as a linear function of bias voltage. As a result, the intensity of the load-pull measurement can decrease up to 80 % as the interpolation of the data with respect to the gate bias voltage can be exploited. The experiment was done on a 4 W GaN technology on-wafer device and the result is verified on 0.2 W GaAs technology device.