Research On High Performance Multimode Load Modulated Power Amplifier

In order to cope with multiple detection service standards and the demand for high integration and low power consumption,radar communication systems are rapidly developing towards multifunctionality and miniaturization,which makes it necessary for power amplifier(PA)to operate in multiple modes and frequency bands;on the other hand,in order to improve spectrum utilization and solve problems such as fast data transmission and other problems,the use of more complex modulation techniques to promote the development of wireless communication systems towards the trend of having high peak-to-average ratio signal,which requires power amplifiers with high efficiency under power fallback.Conventional amplifiers can not guarantee the efficiency of multi-mode work and the performance efficiency will deteriorate when the power is reduced.Load modulated power amplifier has the ability to support multiple operating modes and high efficiency when power is withdrawn,which makes the design more flexible and scalable,but at the same time more complicated to design and difficult to tune than conventional amplifiers.Therefore,this thesis aims to propose a multimode load modulated amplifier architecture to meet the above demand for high performance multimode PA,and to propose a powerful intelligent algorithm to assist in the design of complex PA and shorten the PA design cycle.The main work of this thesis is as follows:1.Firstly,from the demand of RF power amplifier in radar communication system,the potential of realizing high performance multimode load modulated amplifier based on outphasing architecture is analyzed;then the feasibility and necessity of using artificial intelligence algorithm to assist PA design is discussed.This is followed by an overview of the current research status of outphasing,multimode PA and intelligent algorithm-assisted amplifier design.The load modulation theory and the representative combiner theory of outphasing are also introduced through mathematical derivation to set the stage for the following design.2.In the context of modern radar applications,a new multimode outphasing architecture is proposed and a multimode outphasing amplifier MMIC chip operating at 16 GHz is designed and implemented using the Ga As p HEMT process.By implanting a digitally controlled phase shifter into the outphasing,the switching state of the phase shifter is changed to control the change of the specific phase discrepancy between the upper and lower circuits,enabling the switching of the outphasing operating modes.Finally,it achieves flexible the switching of two operating modes,high power mode(saturation state)and low power mode(6d B power fallback state),and has 51.6%and 46.2% efficiency respectively.3.To reduce the PA design cycle and tedious tuning work,a genetic Bayesian multi-objective optimization algorithm is proposed.The algorithm is firstly applied to the automated design of a broadband PA,and the measured results show an average efficiency of 63.1% and an output power between 41 d Bm and 41.9d Bm,verifying the feasibility of the algorithm.Then apply it to the optimized design scenario for load modulated outphasing PA,and a new hybrid objective function is used to optimize the design of the output power combiner matching network for outphasing.A broadband outphasing operating at 2.4-2.7GHz is designed and the measured results show that the minimum efficiency within the operating band is over 53.5% within the 6d B fallback range.The measured results reflect that the optimization algorithm has strong robustness and generalizability,it is also applicable in the optimization design of complex PA.