Abstract
This paper presents a new methodology for designing a broadband three-way Doherty power amplifier (DPA), which utilizes a reactance compensation generated by parallel peaking amplifiers to extend the bandwidth and improve the back-off efficiency. By analyzing the load impedance and efficiency of the reactance-compensated DPA, the optimal reactance at the output of the peaking amplifier required for bandwidth extension can be obtained. Then, a structure using two parallel peaking amplifiers is proposed to reduce the output reactance for the desired distribution. Using a $\lambda _{0}$ /4 transmission line, a sufficiently large output reactance of the peaking branch can be realized at the combining point over a wider frequency band, which can compensate the effective load impedance of the carrier amplifier and improve its efficiency and bandwidth. A wideband three-way DPA is designed and fabricated to verify the proposed method. Measurement results indicate that an efficiency of 50–53% at 10 dB output power back-off and a saturated efficiency of 54–68% can be achieved over the frequency range from 1.6 to 2.7 GHz.
Highlights
In order to improve spectrum utilization and data transmission rate, modern communication systems often adopt complex modulation methods, which leads to modulated signals characterized by large peak to average power ratio (PAPR)
Traditional Doherty power amplifiers (DPAs) can only maintain high efficiency at the 6 dB output power back-off (OPBO) [1]–[7], and cannot be applied to modulated signals characterized by large PAPR
The reactance compensation technique proposed in [23] can be used to extend the bandwidth, the excessive output impedance distribution of the peaking amplifier affects further expansion of its bandwidth. To overcome this major limitation, this paper presents a novel methodology for designing a broadband three-way DPA, which employs the reactance compensation of parallel peaking amplifiers
Summary
In order to improve spectrum utilization and data transmission rate, modern communication systems often adopt complex modulation methods, which leads to modulated signals characterized by large peak to average power ratio (PAPR). To meet the requirements of wireless communication systems, it is of great significance to further extend the DPA bandwidth while maintaining high efficiency at large OPBO. The reactance compensation technique proposed in [23] can be used to extend the bandwidth, the excessive output impedance distribution of the peaking amplifier affects further expansion of its bandwidth. To overcome this major limitation, this paper presents a novel methodology for designing a broadband three-way DPA, which employs the reactance compensation of parallel peaking amplifiers.
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