| Since the acceleration of the development of 5G technology,the demand of RF power amplifiers with high performance is needed to meet with the technology requirement increasingly higher.The performance of LDMOS power devices,which are widely used in RF power amplifiers,directly affects the performance of RF power amplifiers.If the power additional efficiency of RF power amplifier is higher,which means that the need of the DC power is smaller and produce larger output power for the enlarging the RF signal source.Because the transistor is the core component of the power amplifier,under the condition of the magnitude of input signal is high,the efficiency of the power amplifier is related to the nonlinear effect of the transistor.Therefore,we creatively provide a method to improve the power amplifier's power efficiency by optimizing the structure of power device.Based on the power devices provided by the cooperative unit,a series of related experimental tests have been carried out.The main research of this work includes:First,based on the center of the research,referring to the actual measured data of the device,the model is developed which is simulated in the RF circuit simulation environment by using the equivalent electrical characteristic modeling method.The circuit simulation software ADS is used to build and simulate the RF power amplifier.The simulation results are used to analyze the reason of the decrease in the power added efficiency of the power amplifier.Secondly,combined with the mathematical model of the transistor,using the form of the formula theory,the effects of the DC and AC characteristics of the device on the efficiency of the amplifier is studied.The main research is the changes of the transistor's static bias point on the power amplifier's working state and efficiency-related data,and the effect of the transistor's DC non-linear characteristics on the amplifier's power gain.According to the derived formulation,the transconductance and small signal gain which near the bias point of the transistor have impact on the large signal data of the power amplifier,which providing a basic for the following research.Then,according to the two LDMOS power transistor chips provided by the cooperation unit,DC,AC and RF performance tests of these chips were performed.According to the design method of the RF power amplifier,the small-signal S-parameters at the bias point of the device are first tested,and the construction of the power amplifier is completed according to the measured data obtained from the test.At the same time,the large signal test of the power amplifier is accomplished.By comparing the RF largesignal data of the two devices,it is found that the device,the DC characteristics of which is improved and the output power of the power amplifier is also improved,but the additional power efficiency is reduced.According to the actual situation,a scheme to improve the power added efficiency of the power amplifier through the structure of device optimizing is formulated.Finally,based on the results of formulations,an improvement scheme for the original LDMOS transistor is proposed.The DC and AC measured data of the transistor are obtained through the Sentaurus process and electrical simulation.The equivalent electrical characteristics modeling method is used to finish the construction and simulation of power amplifiers in the ADS RF circuit simulation environment.The improved structure is compared with the original two device structures provided by the cooperative unit.Under the same working conditions and with the same matching circuits,the power added efficiency of the power amplifier built by the improved LDMOS device has increased by about 3%,achieving the goal of optimizing the device structure,the power added efficiency of the power amplifier is improved. |
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