The Research On Key Technology Of Load Pull System For GaN Devices

With the development of semiconductor technology,Microwave semiconductor high power devices have been widely used.Accurate measurement of the performance parameters also play a key role in design and use of microwave circuits.Especially,the measurement of various parameters of power devices with high power signal has always been a research hotspot of integrated testing technique.The GaN device is one of the key components of wireless communication because of its high performance and working frequency.The Load Pull measurement system is one of the most advanced methods for measuring large signal parameters to evaluate the GaN power devices.This paper studies the Load Pull system applied to GaN power devices.The work is represented as follows:(1)Through the researchs on basic theory of the Load Pull technique,fully consideration of the power,loss and reflection coefficient was made to meet the characters of the frequency and power of GaN power devices.Finally,the Load Pull measurement system combined with the self-designed dynamic current detection module was established by the electromechanical core for fundamental wave measurement with the frequency ranged from 8 to 28 GHz and the power of 10 W.(2)With the analysis of the working principle of impedance regulator,the control model is fitted by software design,and the measurement and calibration system is set up.Finally the calibration based on vector repeatability and the calibration of the whole system have been completed to meet the test accuracy requirements.(3)To solve the inaccuracy problem of GaN devices in high frequency band,the schemes of multi-frequency band signal drive,Bias Tee network improvement and prematching of devices are designed on the basis of the error analysis,which improve the testing accuracy and the comprehensive coverage of the testing capability of the system.(4)GaN power devices with grid width of 400 um were tested.Under Vds=28V,Idsq=75mA/mm,CW operating condition at 10 GHz,the device exhibits line gain of 14.2dB with power added efficiency of 56.7%,and power density of 8.26W/mm.The changes of output power,gain and power added efficiency of the devices with different frequencies were studied.The results showed that the Load Pull measurement system had good stability,which revealed the efficiency of the test system in actual working monitoring and research assessing of GaN power devices.