Research On Millimeter-Wave GaN-Based High Efficiency MMIC Power Amplifier

As a core component in transceiver module,power amplifiers have been widely used in military aerospace and civil communications.Smaller size,higher frequency and larger output power have become important development trends of power amplifiers with the continuous development of communication technology and aerospace technology.The monolithic microwave integrated circuit?MMIC?PA is undoubtedly the best choice due to its miniaturization and high integration.At the same time,as the representative of the third-generation semiconductor materials,gallium nitride material has many advantages,such as strong breakdown field,high electron mobility and wide band gap,etc.,so that GaN semiconductor devices can output a larger power at a higher frequency,which is favored by relevant researchers.In this study,the working mechanism of AlGaN/GaN HEMT devices is introduced firstly.At the second part,the process of the MMIC is described,which mainly proposed a via-hole cyclic etching method and studied the influence of etching conditions on the via-hole morphology.Then,a scalable equivalent circuit model is established for the passive components involved in the MMIC circuit.A method for extracting parasitic model parameters is proposed for active devices.The effects of different structures and temperature on small signal model parameters are studied.Next,this thesis analyzes the method to improve the efficiency of the PA.Based on this scheme,an X-band high efficiency MMIC PA is developed.Finally,two Q-band MMIC power amplifiers were designed for the application requirements in the millimeter wave band.The main research achievements of this thesis are as follows:?1?The via-hole etching process is optimized,and the cycle etching technique is used to solve the problem effectively that the etching temperature is increased due to the introduction of the paraffin wax,thereby ensuring the etching rate and the via-hole morphology.By changing the etching cooling time ratio,etching power and cavity pressure,the effects of various etching conditions on the etching reaction were analyzed,and the temperature during the process was monitored.The research mainly focuses on the etching dip angle,the via-hole diameter and surface roughness,in order to meet the requirements of via-hole accuracy of devices in the millimeter wave band or even the terahertz band.?2?Research on MMIC passive component scalable equivalent circuit model.In this section,MIM capacitors with different areas,spiral inductors with different turns and thin film resistors with different length are fabricated based on the laboratory process.The S-parameters of the three are measured and the lumped models are established,respectively.The model takes into account the physical structure of passive components and the fitting accuracy is less than 3%in a wide frequency range.The scalability of the model has been demonstrated by the MIM capacitor side length,the number of spiral inductor turns and the film resistance length as independent variables.?3?A new method for extracting parasitic model parameters is proposed.The simplified model of the traditional extraction parasitic capacitance is improved and the series parasitic inductances are introduced.The S-parameters under“Cold-FET”condition are transformed into a Z-parameter matrix and the parasitic capacitances and inductances are obtained by linear regression.The obtained parameters are used to establish a 16-element small-signal equivalent circuit model,which proves the validity of the extracted parameter values.Based on this method,the relationship between the model parameters and temperature is studied and the relationship between the frequency characteristics of the device and the temperature is analyzed.?4?The establishment of the AlGaN/GaN Fin-HEMT equivalent circuit model and the influence of Fin structure on model parameters.According to the structural characteristics of the Fin-HEMT devices,the small signal equivalent circuit model of Fin-HEMT is established for the first time and its RF performance and small-signal characteristics are studied.The influence of the device structure on the model parameters is analyzed by measuring S-parameters of different Fin structure devices and extracting the model parameters of the device under multiple offsets.The results show that the linearity of the Fin-HEMT is mainly caused by the sidewall capacitance effect,the intrinsic saturation velocity improvement and the effective channel wide widening.?5?X-band 50%high efficiency MMIC power amplifier implementation.The working principle of the power amplifier is introduced and the main factors affecting the efficiency of the power amplifier are analyzed.Firstly,it is necessary to determine the best matching impedance of the tansistor under the fundamental and the second harmonic frequency,then select the static operating bias of the deep class AB and extract its model parameters.The research shows that the X-band output capacitor C_ds has a great influence on the harmonic impedance.By designing the peripheral compensation structure,the second harmonic impedance value of the intrinsic current source reference plane is close to the open circuit point.The test results show that the MMIC peak efficiency can reach 57.7%in the X-band frequency range,and the chip area is 12mm^2,which has superior performance compared with the MMIC power amplifier reported in this band.?6?Q-band MMIC power amplifier design.37⁴2.5GHz is designated as the 5G communication band by the Ministry of Industry and Information Technology.In the view of the current millimeter wave application requirements,this section designs two Q-band MMIC PA.One is a driver MMIC PA based on GaAs technology,and the other is a high-power MMIC PA based on GaN process.This section describes in detail the design process of MMIC PA,which adopts the circuit matching structure of high-pass filter,suppressing low-frequency,and combines impedance matching and power synthesis to simplify matching structure,ensure bandwidth and reduce matching loss.The results show that in the frequency range of 37⁴3GHz,P_-1dB is 26dBm,the power added efficiency is 31%and the power gain is 29dB for the drive PA;the P_sat for the final PA is 38dBm,the PAE is 22.3%,and the power gain is 16.5dB.Compared with the products near this frequency band,both two Q-band PAs designed have excellent performance.