Research And Design Of High Power Medium And Long Wave Power Amplifier Based On GaN

Medium and long wave communication is a kind of radio communication which uses medium and long wave band electromagnetic wave as transmission medium in the process of information transmission.it has the characteristics of slow attenuation rate,long communication distance,stable communication,basically unaffected by other landforms and so on.Medium-long wave power amplifier as a key component of medium-long-wave communication system,the design of medium-long-wave power amplifier with high power,high efficiency and high harmonic suppression rate has important theoretical significance and practical value.This paper designs a high-power medium-long-wave power amplifier based on gallium nitride(GaN)devices.After analyzing and studying the characteristics of GaN HEMT and the key technologies of medium-long-wave power amplifier,the whole system is designed.The main contents are as follows:First,the research background and current situation of GaN medium and long wave power amplifier are analyzed,the design requirements and indicators of GaN high power medium and long wave power amplifier are defined,the system workflow analysis and the division of software and hardware modules are completed,and the overall design scheme of the whole system is determined.Second,the switching characteristics and crosstalk characteristics of GaN HEMT are analyzed and studied.The effects of gate resistance,parasitic capacitance and parasitic inductance on the switching characteristics of GaN HEMT are analyzed,and the effects of these parameters on the switching characteristics are analyzed and discussed through the changes of gate-source voltage,drain-source voltage and drain current.At the same time,the principle analysis and derivation modeling of the GaN HEMT bridge arm crosstalk problem are carried out,and some main factors of the bridge arm crosstalk problem are studied and analyzed to provide help for the use of GaN HEMT.Third,the key technologies of medium and long wave power amplifier are analyzed and studied,including GaN drive circuit bridge arm crosstalk suppression method,high power digital power amplifier topology,multi-order filter,coupler and so on.Fourth,the software and hardware system of GaN medium and long wave power amplifier is designed.First of all,the modular hardware circuit is designed.the hardware system module includes: the signal conditioning circuit module to realize the small signal processing and circuit protection function;the power amplification synthesis module to realize the small signal power amplification and superposition function;the power signal processing module to realize the harmonic suppression,power coupling and relay switching function;the control circuit module to realize the whole machine control;the whole machine antiinterference design and so on.Secondly,it completes the software design of power amplifier information collection,communication task realization,running state control and so on.Fifth,after the completion of the whole machine construction,the whole machine is verified and tested.The frequency response range of the GaN medium and long wave power amplifier system is 200k～400kHz,which can reach the output active power 5000 W under 50 ohm load,the machine efficiency 85%,the second harmonic suppression 50 dB,the third harmonic suppression 50 dB,and has the characteristics of high power,high efficiency and high harmonic suppression rate.