Passive Parameter Measurement And Modeling Of Gan Transistor

RF power amplifier is one of the main components of 5G wireless communication base station,the inaccurate performance indicators of power amplifier will affect the circuit system.In order to enhance the accuracy of the system and the predictive power of the simulation circuit,the design of the power amplifier circuit needs to use an accurate model of the power device.This thesis takes packaged GaN transistor as the modeling object and focuses on the test fixture and TRL method for de-embedding,the small signal S parameters of GaN transistor under various bias voltages are measured,and the passive parameters such as parasitic element and nonlinear capacitance of GaN transistor model are extracted by using the small signal S parameters.The main research contents can be summarized as follows:First of all,the research history of GaN transistor measurement and modeling is reviewed which reflects that modeling is of significance.Also,the packaged GaN transistor needs to be tested by using the test fixture.Secondly,the calibration method for test system is proposed.The calibration kits are designed by using the calibration principle of TRL.In the range of 1GHz to 5GHz,the test system is calibrated by using the calibration method to eliminate the i nfluence of the test fixture on the test results.Then,the test scenario of GaN transistor is proposed,and a welding-free test fixture is designed.In this test fixture,the same set of coaxial joints is used to test the calibration kits and the device by means of pressing in order to avoid the random error caused by the inconsistent performance of the joints.The testing range of the test fixture is 40mm-150 mm in length and 10 mm in thickness.A test interface integrated with TRL calibration algorithm is designed to interact with the vector network analyzer.Finally,the small signal equivalent circuit model based on EEHEMT model is proposed.The calibrated test system is used to test the small signal S parameters of GaN transistors with different bias voltages,and the values of passive parameters such as parasitic components and nonlinear capacitors in the model are extracted,and the model simulation S parameters are compared with the test S parameters.A complete model is obtained by combining the passive parameters with the large signal part of the existing EEHEMT model,and a power amplifier operating at 3.3GHz-3.6GHz is designed by using this model.The test results show that the calibration method and test fixture used in this thesis can satisfy the test system calibration within the range of 1GHz-5GHz and the test of GaN transistor small signal S parameters.The measured S parameters are used to obtain the passive parameter value in the model.The model uses the extracted passive parameter value to simulate the S parameters,and the results are in good agreement with the measured S parameters.The above results verify that the test method and modeling method are feasible.