Abstract
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.
Highlights
T HE Doherty power amplifier (DPA) is widely adopted in mobile base-stations for its ability in amplifying modulated signals with high peak-to-average power ratio (PAPR) while maintaining high efficiency [1], [2]
Several licensed bands are assigned to 4G systems, especially in the 1.6–3.5 GHz range, making the design of DPAs able to operate on different bands of great interest for the provision of a single hardware configurable to the specific frequency adopted in the small cell
The gain compression/expansion can be estimated as the difference between input power back-off (IBO) and output power back-off (OBO), where the back-off is the power range between the Doherty breakpoint and maximum power
Summary
T HE Doherty power amplifier (DPA) is widely adopted in mobile base-stations for its ability in amplifying modulated signals with high peak-to-average power ratio (PAPR) while maintaining high efficiency [1], [2].
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