Recent Developments of Dual-Band Doherty Power Amplifiers for Upcoming Mobile Communications Systems

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.

Antenna for 5G mobile Communications Systems at 10 GHz

The design of compact dual band grid array antenna (GAA) designed on FR-4 substrate for future Fifth Generation (5G) Mobile Communications at 10 GHz is reported. The proposed antenna uses coaxial technique of feeding and has a dimension of 48 mm × 55 mm × 1.6 mm. Simulation results using CST microwave studio illustrates that the antenna has a band from 10.03 GHz to 10.68 GHz and another band from 10.7 GHz to 12.23 GHz. This excludes the 10.68 – 10.7 GHz band in which emissions were forbidden by the Radio Regulations in the sense that it has been allocated for the Radio Astronomy, Space Research and Earth Exploration Satellite (passive). The antenna has a maximum gain of 8.03 dBi at 10 GHz, thus a good candidate for the future 5G mobile communications.