Research On High Efficiency Of Short-Wave Power Amplifier

HF communication has been widely used in the fields of voice,telegraph and data transmission because of its advantages such as simple equipment,convenient networking and strong resistance to destruction.Especially,in military remote communication,HF communication occupies an extremely important position.It is worth mentioning that HF communication is being valued increasingly in the defense and military.HF communication is required to have higher transmission speed,higher transmission reliability,higher probability of transmission,stronger ability of anti-interference and business.The output power of transmitter and the other index are required higher and higher.Power amplifier is the key device in communication system.It is located at the end of the transmitter and is the unit which consumes the most energy and produces the highest heat in the whole system.The energy consumption,stability,and the requirements to the power and the heat dissipating device of the whole transmitter system are directly determined by power amplifier.Under the condition of the international green communication,improving the efficiency of power amplifier is a problem to be considered.Doherty power amplifier has the advantages of simple structure,low cost and in the situation of power-retreat efficiency is significantly improved.Meanwhile,combining with the pre-distortion technology,the overall linearity of power amplifier can be improved.So the technology of Doherty is considered as one of the most promising technologies to improve the efficiency of RF power amplifier.The paper has carried out a comprehensive study of the HF power amplifier which has high efficiency.Firstly,this paper starts with the basic knowledge of HF communication and has a conclusion that HF communication is still a kind of important remote communication method which can't be replaced at present,combining with the application and key technology of the short wave communication system.Therefore,HF communication has important research value and application value.Secondly,this paper has carried out a detailed study of the power amplifier and put forward that the design of the amplifier must have a high linearity in order to reduce the spectrum spreading and the envelope distortion.Several measures to improve the linearity of the power amplifier have been given:improving the linearity of the device in terms of technology and material,making the amplifier retreat to the linear area and using the linearization technique for the correction of the working of amplifier in the nonlinear area.By comparing,it concludes that pre-distortion and feed-forward are the most commonly techniques to improve the linearity of the amplifier.With the application of multi-carrier technique and broadband communication in HF communication system,it concludes that the use of pre-distortion is the most effective technology to improve the linearity of HF communication system.The theory of load/source pull is determined to complete the high efficiency design of Doherty power amplifier.Lastly,combining with the characteristics of short-wave signal and the whole requirement to improve the efficiency of power amplifier,the circuit has been designed to realize the high efficiency for power amplifier which is suitable for HF communication.And the simulation experiment has been done by automatic simulation software(ADS)which has powerful functions and wide applications in radio frequency circuit.At the same time,the element parameters have been modified repeatedly.The summary of the full paper and the work that can improve have been given at the end of the paper.