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We report on the synthesis and characterization of CsSnI3 perovskite semiconductor thin films deposited on inexpensive substrates such as glass and ceramics. These films contained polycrystalline domains with typical size of 300 nm. It is confirmed experimentally that CsSnI3 compound in its black phase is a direct band-gap semiconductor, consistent with the calculated band structure from the first principles. The band gap is determined to be ∼1.3 eV at Γ point at room temperature.

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).

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This work discusses the efficiency bandwidth constrains in Doherty amplifiers. An analysis of the bandwidth limitations imposed by the impedance inverter and output capacitance of the active devices is given.Alternative wideband matching and output connection schemes for Doherty amplifiers are evaluated for their efficiency performance both at full output power, as well as , in power back-off operation. The presented theory is verified using a Doherty demonstrator amplifier, which allows independent control of the input signals for the main and peak device. The related measurements show the largest high-efficiency bandwidth reported up to date for a Doherty amplifier.