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Tunable matching networks (MNs) are essential components for agile radio frequency systems. To optimally design such networks, the total area they cover on the Smith chart needs to be determined. In this paper, the coverage areas of typical MNs have been determined analytically for the first time. It has been found that the coverage area is encompassed by up to five arcs. Analytical expressions for the centers and radii for these arcs have been derived. The theoretical analysis is provided for four typical MNs and verified by circuit simulation and measured data. Moreover, a dynamically load-modulated power amplifier has been designed using the presented theoretical techniques, which demonstrates a measured improvement in the power added efficiency of up to 5% in the frequency range of (0.8–0.9) GHz. [ABSTRACT FROM AUTHOR]

In this article, Doherty power amplifier (DPA) with dynamic load modulation (DLM) is proposed for wireless communications with high peak-to-average ratio (PAR) signals. The proposed DPA with DLM operates as a conventional DPA from peak to 6-dB back-off powers, and DLM starts to operate at lower power than 6-dB back-off. The DPA with DLM was designed using 6-W GaN high mobility transistors (HEMTs) at 1.85 GHz. The fabricated DPA with DLM shows a power-added efficiency (PAE) of 44.7% at 10-dB back-off power of continuous-wave input signal, which is 5% higher than that without DLM. Dynamic measurement was also carried out using 3.84 MHz W-CDMA signal with 7.4 dB PAR. The measurement of the DPA with DLM exhibits an average PAE of 32.1% at output power of 27.1 dBm, and adjacent channel leakage ratio (ACLR) of −45.1 dBc, which corresponds to 6.1% improvement in PAE compared with the DPA without DLM. [ABSTRACT FROM AUTHOR]

This paper presents a novel adaptive power amplifier (PA) architecture for performing dynamic-load-modulation. For the first time, a dynamically-load-modulated PA design that achieves octave bandwidth, high power and high efficiency simultaneously is experimentally demonstrated. This PA design is based on a commercial GaN HEMT. The output matching scheme incorporates a broadband static matching for high-efficiency at the maximum power level and a wideband dynamic matching for efficiency enhancement at power back-offs. The impedance and frequency tunability is realized using silicon diode varactors with a very high breakdown voltage of 90 V. Experimental results show that a dynamic-load-modulation from maximum power to 10-dB back-off is achieved from 1 to 1.9 GHz, with a measured performance of \approx10-W peak power, \approx10-dB gain, 64%–79% peak-power efficiency, and 30%–45% efficiency at 10-dB power back-off throughout this band. [ABSTRACT FROM PUBLISHER]

In this paper, a novel model is proposed for dual-input high efficiency power amplifier (PA) architectures, such as envelope tracking (ET) and varactor-based dynamic load modulation (DLM). Compared to the traditional single-input modeling approach, the proposed model incorporates the baseband supply voltage/load control as an input. This advantage makes the new approach capable to achieve maximized average power-added efficiency (PAE) and minimized output distortion simultaneously. Furthermore, the new approach has shown to be robust towards time misalignment between the RF input and baseband supply voltage/load control signals, and it can be applied with a reduced-bandwidth baseband supply voltage/load control. Experiments have been performed in a varactor-based DLM PA architecture to evaluate the new modeling approach. The results show that it can achieve 9 and 7 dB better performance than the traditional approaches in terms of adjacent channel leakage ratio and normalized mean square error, respectively. At the same time, the average PAE is maximized. Similar results have been achieved with the proposed model even when reduced-bandwidth baseband load control signal is used or time misalignment between the RF and baseband load control input signals exists. Although the new approach is only tested with DLM architecture in this paper, it is very general and can be applied to ET architectures as well. [ABSTRACT FROM AUTHOR]