Modeling Approaches for Active Antenna Transmitters
MIMO systems exploit active antenna arrays transmitter configurations to obtain higher energy efficiency and beamforming flexibility. The analysis of transmitters in MIMO systems becomes complex due to the close integration of several antennas and power amplifiers (PAs) and the problems associated with heat dissipation. Therefore, the transmitter analysis requires efficient joint EM, circuit, and thermal simulations of its building blocks, i.e., the antenna array and PAs. Due to small physical spacing at mmWave, bulky isolators cannot be used to eliminate unwanted interactions between PA and antenna array. Therefore, the mismatch and mutual coupling in the antenna array directly affect PA output load and PA and transmitter performance. On the other hand, PAs are the primary source of nonlinearity, power consumption, and heat dissipation in transmitters. Therefore, it is crucial to include joint thermal and electrical behavior of PAs in analyzing active antenna transmitters.
In this thesis, efficient techniques for modeling active antenna transmitters are presented. First, we propose a hardware-oriented transmitter model that considers PA load-dependent nonlinearity and the coupling, mismatch, and radiated field of the antenna array. The proposed model is equally accurate for any mismatch level that can happen at the PA output. This model can predict the transmitter radiation pattern and nonlinear signal distortions in the far-field. The model's functionality is verified using a mmWave active subarray antenna module for a beam steering scenario and by performing the over-the-air measurements. The load-pull modeling idea was also applied to investigate the performance of a mmWave spatial power combiner module in the presence of critical coupling effects on combining performance.
The second part of the thesis deals with thermal challenges in active antenna transmitters and PAs as the main source of heat dissipation. An efficient electrothermal modeling approach that considers the thermal behavior of PAs, including self-heating and thermal coupling between the IC hot spots, coupled with the electrical behavior of PA, is proposed. The thermal model has been employed to evaluate a PA DUT's static and dynamic temperature-dependent performance in terms of linearity, gain, and efficiency.
In summary, the proposed modeling approaches presented in this thesis provide efficient yet powerful tools for joint analysis of complex active antenna transmitters in MIMO systems, including sub-systems' behavior and their interactions.
Active antenna transmitter
active subarray antenna
Chalmers, Mikroteknologi och nanovetenskap (MC2), Mikrovågselektronik
A Wideband and Low-Loss Spatial Power Combining Module for mm-Wave High-Power Amplifiers
IEEE Access,; Vol. 8(2020)p. 194858-194867
Artikel i vetenskaplig tidskrift
Hybrid Beamforming Transmitter Modeling for Millimeter-Wave MIMO Applications
IEEE Transactions on Microwave Theory and Techniques,; Vol. 68(2020)p. 4740-4752
Artikel i vetenskaplig tidskrift
P. Taghikhani, K. Buisman, M. Versleijen, J. Ramon Perez-Cisneros and C. Fager, "Temperature-aware Characterization of Power Amplifiers Using an Efficient Electrothermal Analysis Technique''
Modern wireless communications systems use several branches of active antennas, working together, for higher energy efficiency and beamforming flexibility. Putting many branches close together increases heat dissipation challenges. Cooling is not sufficient, and thermal management is a must-have before implementing the system. In transmitters, many subsystems work together, each described by specific physics.
In my thesis, I propose efficient methods for the analysis of complicated transmitter architectures. With the method I have provided, it is possible to predict the signal's quality received by the user accurately, considering the effect of heat dissipation, antenna radiation, and electrical circuit behavior. Therefore, the system designer can use these methods to develop highly energy-efficient and reliable communication for users. Mobile users always will be connected to make a high-quality video call when they are thousands of kilometers away from each other.
Informations- och kommunikationsteknik
Elektroteknik och elektronik
Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5069
Chalmers tekniska högskola
The defence will be held in Kollektorn and online
Opponent: Prof. Aarno Pärssinen, University of Oulu, Faculty of Information Technology and Electrical Engineering