Research On Key Technologies For Millimeter-wave,Broadband And High Effieiency Power Amplifier Chips

With the development of wireless technology,the electronic systems need higher frequency to meet the growing demand.Due to the advantages of spectrum resources,millimeter-wave has gradually attracted lots of research interesting.The ultra-broadband systems have shown applications widely used in communications,radars and electronic warfare.The ultra-broadband power amplifier is one of the key technologies,and the broadband frequency,the efficiency and the output power will promote the development of the systems.For Si and GaAs substrate,the output power and efficiency are limited.The 3^rd generation semiconductor,represented by GaN,due to the advantages of wide band gap and high thermal conductors,can improve the voltage and output power of transistors and become one of the research focuses.Some research on key technologies to improve the self-heating modeling,trapping modeling,and the broadband power amplifier design has been done in this dissertation.The main research are summarized as follow,1.The self-heating modeling.Due to the lack of differentiating the current reduction from self-heating,there are five thermal parameters related to thermal,and their fitting parameters contain tanh function,which is not easy for extraction.Thus,a quasi constant temperature-thermal current reduction method is proposed.Based on the assumption that the thermal effect of short pulse could be neglected and the junction temperature remained the same as the room temperature,the short pulses at different temperature are used to extract the thermal parameters.Meanwhile,long pulses results are used to extract the self-heating subcircuit.Thus,the current reduction is differentiated from the self-heating clearly.The extraction and modeling are simplified.Only two parameters(I_pkth and P₁)are related to current reduction,and their fitting coefficients(K_p1 and K_Ipk)are constant.2.The physical trapping modeling.In this work,the analytical expression of transient pulse response is derived from the current differential equation of the original SRH model.We found that it still can’t model the different time constants corresponding to trapping and de-trapping and can’t model the pulse I-V curves including trapping and de-trapping.In order to solve these difficulties,the semi-SRH method was proposed.The time constant for trapping is considere to be infinitesimal approximately,while the SRH model is still used for de-trapping.This improved method can model the different time constants and pulsed I-V including trapping and de-trapping.3.Parasitic elements influence on harmonic impedance tuned power amplifier.In order to reduce the contradiction between the second harmonic impedance of 18-20GHz and the fundamental impedance of 36-40 GHz,the parasitic elements effects on the impedance coverage mapping method is proposed.From the aspect of impedance mapping between transistor package plane and current generator plane,it is proved that the parasitic parameters reduce the harmonic tuned effect and ease the above contradiction.The reduced and rotated projection of parasitic elements between the two planes becomes clear due to this analysis.The 2^nd harmonic Load-Pull simulation shows that comparing the modeling without parasitic elements and the original modeling,the PAE variation range reduces from 34.1%-62.1%to 40.8%-53%.Thus,the simulation agrees with the theoretical analysis.4.Broadband power amplifiers using STN（Synthesized Transformer Network）.The new TPM（Transmission Poles Method）is introduced to analyze STN,instead of the conventional RFM（Resonant Frequencies Method）.TPM can calculate the character of STN more accurately,and derive the limitation for impedance transformation ratio and power.The first RM（Reactive Matching）power amplifier covering 18-40 GHz have been designed,and the PAE is 17-23.6%.5.N-order STN.From TPM,the impedance transformation ratio of 1-order STN has a maximum value T_MAX1N,which limits the output power.The 2-order STN was proposed to improve the impedance transformation ratio maximum value to T_MAX2N=(T_MAX1N)²,with the same transmission poles.It can be further extended to the N-order STNs,with the impedance transformation ratio maximum value T_MAXnN=(T_MAX1N)ⁿ.A RM power amplifier using 2-order STN and combing 4transistors,can cover 18-40GHz and provide>31.9dBm output power.Compared with the previous power amplifier,this output power increases about 1.9dBm.