Sequential Power Amplifier Research Articles

Development Review of Highly Efficient Sequential Power Amplifier with Extended Back-Off Range for Broadband Application

Similar to a Doherty power amplifier (DPA), a sequential power amplifier (SPA) is mainly composed of a main amplifier, an auxiliary amplifier and a combiner. However, SPA breaks the bandwidth limitation of the impedance inverter in the DPA, and also simplifies the design procedure. Since the main amplifier has no load modulation, it is easy for the SPA to realize broadband operation and improve the output back-off (OBO) power range. Therefore, SPA has great advantages and potential in expanding bandwidth, improving drain efficiency and expanding the back-off range of a power amplifier simultaneously. This paper describes the evolution and classification of the SPA. First, the basic theory of the SPA is reviewed. Then, some two-way SPAs using coupler and circulator as a power combiner are discussed. Thirdly, the latest popular sequential load modulated balanced amplifier is overviewed.

Design of a Dual-Band Load-Modulated Sequential Amplifier with Extended Back-off

This letter presents a dual-band load-modulated sequential amplifier (LMSA). The proposed amplifier changed the attenuator terminated at the isolation port of the four-port combiner of the traditional sequential power amplifier (SPA) architecture into a reactance modulation network (RMN) for load modulation. The impedance can be maintained pure resistance by designing RMN, thus realizing high efficiency and a good portion of the output power in the multiple bands. Compared to the dual-band Doherty power amplifier with a complex dual-band load modulation network (LMN), the proposed LMSA has advantages as maintaining high output power back-off (OBO) efficiency, wide bandwidth and simple construction. A 10-watt dual-band LMSA is simulated and measured in 1.7-1.9 GHz and 2.4-2.6 GHz with saturated efficiencies 61.2-69.9% and 54.4-70.8%, respectively. The corresponding 9 dB OBO efficiency is 46.5-57.1% and 46.4-54.4%, respectively.

Look‐up table method for optimising coupling ratio in broadband sequential power amplifiers

This study reappraises the optimum design parameters for the sequential power amplifier (SPA) when taking relative phase difference into account. By including the phase relationship between the main and peaking amplifiers, a modified efficiency formulation is derived that reveals the impacts of the key design parameters on the SPA efficiency at output power back-off. To optimise a wideband high-efficiency SPA design, a look-up table method is used to predict the required coupling ratio for a wideband directional coupler. To validate the design approach, a 1.5–2.4GHz SPA is designed and measured, showing drain efficiency higher than 40% at 6dB back-off across the band. When characterised using a 20MHz long term evolution (LTE) signal and digital predistortion, the SPA shows good linearity with error vector magnitude <1.3%, and adjacent channel leakage ratio levels better than −45 dBc across the band.

Design of a dual-band sequential power amplifier

In this article, we present a dual-band sequential power amplifier (SPA) to provide high efficiency at power back-offs and maximum output power at two separate working frequencies. The proposed SPA, including a carrier amplifier, a peaking amplifier, a power divider, and a combing coupler, is fabricated on Isola I-TeraMTRF boards with 3.45 dielectric constant, 0.0028 loss tangent, and 0.508 mm substrate thickness. The SPA provides 48 and 62% drain efficiency (DE) at 6 dB output back- off (OBO) and maximum output power at 1.1 GHz (first design frequency), and it also provides 52 and 65% DE at 6 dB OBO and maximum output power at 1.5 GHz (second design frequency). The designed SPA achieves above 39 dBm output powers at two working frequencies with about 10 dB gain and ±1.3 dB gain flatness. To the best of the authors’ knowledge, it is the first time that a dual-band SPA is reported and demonstrated experimentally. © 2016 Wiley Periodicals, Inc. Microwave Opt Technol Lett 58:99–102, 2016

Design of a tunable sequential power amplifier

ABSTRACTA tunable sequential power amplifier (SPA) is presented in this article. The proposed SPA, including a tunable coupler, a carrier amplifier, a peaking amplifier, and a combining coupler is fabricated on Isola I‐TeraMTRF boards with 3.45 dielectric constant and 0.508 mm substrate thickness. A conventional SPA (nontunable) is also designed for reference and performance comparison. Measurement results show that the tunable SPA provides about 2 dB higher gain and 1 dB higher power output comparing with the reference design. The measurement results match well with the analysis. © 2015 Wiley Periodicals, Inc. Microwave Opt Technol Lett 57:2899–2901, 2015

Broadband Sequential Power Amplifier With Doherty-Type Active Load Modulation

This paper presents the concept and the detailed analysis of a sequential power amplifier with Doherty-type active load modulation (SPA-D). By introducing a Doherty-type output combiner into the conventional sequential power amplifier (PA), highly efficient amplification over broadband and wide dynamic range for the reconfigurable output power back-off can be achieved. The proposed amplifier mimics both the sequential and the Doherty PAs by exploiting the active load modulation region that has not been considered in the design of Doherty amplifiers. A broadband SPA-D prototype having 8-dB output back-off power (OBO) is designed and implemented. The experimental results exhibit drain efficiencies of 50%-75% at 7-10-dB OBO and 57%-70% at peak power with Doherty-like behavior over 700-MHz bandwidth centered at 2.35 GHz. The ability to easily reconfigure the breakpoint is experimentally verified, providing a convenient means for optimizing the amplifier efficiency according to various wireless standards. In addition, by using a memoryless digital predistortion, the spectrum emission mask required for long-term evolution down link can be fulfilled, making it well suited for applications in modern wireless transmitters.