Abstract
Power amplifiers in modern and future communications should be able to handle different modulation standards at different frequency bands, and in addition, to be compatible with the previous generations. This paper reviews the recent design techniques that have been used to operate dual-band amplifiers and in particular the Doherty amplifiers. Special attention is focused on the design methodologies used for power splitters, phase compensation networks, impedance inverter networks and impedance transformer networks of such power amplifier. The most important materials of the dual-band Doherty amplifier are highlighted and surveyed. The main problems and challenges covering dual-band design concepts are presented and discussed. In addition, improvement techniques to enhance such operations are also exploited. The study shows that the transistor parasitic has a great impact in the design of a dual-band amplifier, and reduction of the transforming ratio of the inverter simplifies the dual-band design. The offset line can be functionally replaced by a Π-network in dual-band design rather than T-network.
Highlights
The demands for increasing the amount of data that can be transmitted within a limited bandwidth is continuing to grow rapidly, especially with developments, where users are being attracted by multimedia data and video streaming, as well as the Internet of Things technology revolution.the 5G mobile generation will include several technologies that can help to achieve its promised goals
Shao et al [19] modified the structure of a Doherty power amplifier (DPA) so that they eliminated the effect of the series and two in shunt), as shown in Figure 10, in order to make the proposed DPA works in dual-band impedance inverter at the output of classical DPA, and in addition used four transmission line according to the equations proposed by Chuang [33]
In [62], a 3-way Doherty power amplifier targeting 1.8–2.2 GHz frequency bands suitable for mobile base-stations was achieved depending on LDMOS RFIC technology, a 47% efficiency accomplished at 12 dB back-off
Summary
The demands for increasing the amount of data that can be transmitted within a limited bandwidth is continuing to grow rapidly, especially with developments, where users are being attracted by multimedia data and video streaming, as well as the Internet of Things technology revolution. Modern power amplifiers should be designed to produce high efficiency at a large output power back-off (OBO); known efficiency enhancements techniques include: Doherty linearity. Modern(DPA), power envelope amplifierselimination should be designed to produce high efficiency at a large output power amplifier and restoration (EER), envelope tracking (ET), and power back-off (OBO); known efficiency enhancements techniques include: Doherty power amplifier linear amplification using nonlinear components (LINC), and Chireix out-phasing. New terms have entered the communications systems the Doherty amplifier, where neither signal processing blocks nor additional controlling circuits are which are multi-band and multi-mode, where the term “multi-band” refers to a transmitter which required. The term “multi-mode” refers to a transmitter can frequency bands simultaneously; in this case, the number of devices, size, and cost will be reduced.
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