Abstract-A three-way Doherty 100-W GaN base-station power amplifier at 2.14 GHz is presented. Simple, but accurate design equations for the output power combiner of the amplifier are introduced. Mixed-signal techniques are utilized for uncompromised control of the amplifier stages to optimize efficiency, as well as linearity. The combination of the above techniques resulted in an unprecedented high efficiency over a 12-dB power backoff range, facilitating a record high power-added efficiency for a wideband code division multiple access test signal with high crest factor, while meeting all the spectral requirements for Universal Mobile Telecommunications System base stations.Index Terms-Base station, Doherty, high efficiency, mixed signal, power amplifier, predistortion, Universal Mobile Telecommunications System (UMTS), wideband code division multiple access (W-CDMA).
Abstract-A 90-W peak-power 2.14-GHz improved GaN outphasing amplifier with 50.5% average efficiency for wideband code division multiple access (W-CDMA) signals is presented. Independent control of the branch amplifiers by two in-phase/quadrature modulators enables optimum outphasing and input power leveling, yielding significant improvements in gain, efficiency, and linearity. In deep-power backoff operation, the outphasing angle of the branch amplifiers is kept constant below a certain power level. This results in class-B operation for the very low output power levels, yielding less reactive loading of the output stages, and therefore, improved efficiency in power backoff operation compared to the classical outphasing amplifiers. Based on these principles, the optimum design parameters and input signal conditioning are discussed. The resulting theoretical maximum achievable average efficiency for W-CDMA signals is presented. Experimental results support the foregoing theory and show high efficiency over a large bandwidth, while meeting the linearity specifications using low-cost low-complexity memoryless pre-distortion. These properties make this amplifier concept an interesting candidate for future multiband base-station implementations.Index Terms-Base station, high-efficiency RF power amplifier, mixed-mode amplifier, outphasing amplifier, wideband code division multiple access (W-CDMA).
In tbis paper the analy& and design of a 2OOW classical Doherty amplifier is described using dlscrete LDMOS devices. The peak (class-C) and main (class-AB) amplifiers are desigbed with two stages to obtain flat AM-AM and AM-PM charPCteristics for the Doherty amplifier. An asymmetrical planar coupler structure is u W e d as an input splitter and microship based elements are used for phase matching and power combloing at the output. Thh Doherty PA has a measured PldB of 53dBm and exhibits an efiiciency of 34% at 6dB backoff (47") for two-carrier WCDMA. The ACPR and IM3 obtained at 47dBm are 37dBc and 33dBc respectively. The gain at 6dB backoff is ZZdB over the frequency range 2.11-2.17GHz Design considerations for a Doherty ampMer based on discrete LDMOS devices are addressed.
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