Nonlinear Characterization of Wideband Microwave Devices and Dispersive Effects in GaN HEMTs
Doctoral thesis, 2018
A measurement setup for wideband, nonlinear characterization of microwave devices has been designed and verified. The setup allows for simultaneous acquisition of low-frequency and radio-frequency signals from DC up to 4~GHz through the use of wideband signal generators and measurement receivers. This enables measurement scenarios such as multi-band load-pull and large-signal characterization of IQ-mixers, which can give useful insight into how to optimize the performance in a RF transmitter.
Electrothermal characterization of GaN devices has been carried out using conventional measurement methods such as pulsed I-V, and it is shown that trapping phenomena and thermal effects due to self-heating or mutual coupling are challenging to separate. Multiple methods must be utilized to fully characterize both the large-signal and small-signal impact on device performance. A new characterization method has been developed, for extraction of thermal transfer functions between mutually coupled devices on e.g. a semiconductor wafer. The method does not require any DC-bias on the measured devices, which can potentially reduce the influence of trapping during characterization of thermal properties in materials.
Chalmers, Microtechnology and Nanoscience (MC2), Microwave Electronics, Microwave Electronics
Vector-corrected Nonlinear Multi-port IQ-mixer Characterization using Modulated Signals
IEEE MTT-S International Microwave Symposium Digest,; (2017)p. 1433-1436
Paper in proceedings
Wideband RF characterization setup with high dynamic range low frequency measurement capabilities
2016 87th ARFTG Microwave Measurement Conference,; (2016)
Paper in proceedings
An Oscilloscope Correction Method for Vector-Corrected RF Measurements
IEEE Transactions on Instrumentation and Measurement,; Vol. 64(2015)p. 2541-2547
Dispersive Effects in Microwave AlGaN/AlN/GaN HEMTs With Carbon-Doped Buffer
IEEE Transactions on Electron Devices,; Vol. 62(2015)p. 2162-2169
A Novel Active Load-pull System with Multi-Band Capabilities
81st ARFTG Microwave Measurement Conference,; (2013)
Paper in proceedings
Gustafsson, S., Bremer, J., Bergsten, J., Buisman, K., Malko, A., Grünenpütt, J., Madel, M., Blanck, H., Rorsman, N.,Thorsell, M. "Methods for Electrothermal Characterization of GaN HEMT Structures"
Nonlinearities in microwave circuits can for example arise through intentional overdrive for high efficiency operation or due to non-idealities in components. Modern cellular standards such as 4G, and the upcoming 5G standard, use communication signals with wide bandwidths to allow for higher data throughput in the cellular networks. Therefore, distortion due to nonlinearities is of increasing importance to study using wideband signals. As such, a wideband nonlinear measurement setup has been designed and verified in this thesis.
Designing high performance circuits for next generation wireless applications also requires the utilization of semiconductors with better material properties compared to silicon, such as gallium nitride (GaN). With GaN, higher output powers at higher frequencies are possible to obtain, allowing for e.g. higher data rates at longer distances between the base station and cell phone. However, GaN suffers from performance-degrading effects such as electron trapping, which is a result of defects in the GaN material. In order to understand these effects, and to be able to optimize the GaN material, there is a need for measurements which can capture trapping phenomena in a methodical way. This thesis also deals with characterization of such phenomena.
The measurement instruments and methods developed in this thesis can aid in the understanding of nonlinear phenomena, enabling the design of high performance circuits for next generation wireless applications.
Areas of Advance
Nanoscience and Nanotechnology (2010-2017)
Other Electrical Engineering, Electronic Engineering, Information Engineering
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 4439
Chalmers University of Technology
Opponent: Prof. Paul J. Tasker