Interference Robust RF Beamforming Transceivers for mmWave and Beyond
Thesis event information
Date and time of the thesis defence
Place of the thesis defence
Wetteri auditorium IT 115
Topic of the dissertation
Interference Robust RF Beamforming Transceivers for mmWave and Beyond
Doctoral candidate
Master of Science (Tech) Muhammad Yasir Javed
Faculty and unit
University of Oulu Graduate School, Faculty of Information Technology and Electrical Engineering, Centre for Wireless Communications - Radio Tehnologies
Subject of study
Radio Engineering
Opponent
Assistant Professor Yanki Aslan, Delft University of Technology, The Netherlands
Custos
Professor Aarno Pärssinen, University of Oulu
Interference Robust RF Beamforming Transceivers for mmWave and Beyond
Phased arrays are used in transceivers at millimeter wave (mmW) and higher frequencies to account for path losses and produce extremely directional beamforming gains. Spatial signal leakage, however, may lower the signal-to-interference-plus-noise ratios (SINRs) of other users in different directions, hence reducing their throughputs. The challenge of error-free signal detection in the presence of spatial interference frequently calls for complicated, power-hungry radio frequency (RF) components with a high dynamic range to deliver the required SINRs.
Most interference reduction techniques, both in theory and in practice, require one to control the amplitude of the antenna paths, which results in inefficient use of available power by the power amplifiers, reducing effective isotropic radiated power (EIRP) and, as a result, coverage.
This thesis explores several dynamic beamforming scenarios and strategies for decreasing interference in phased array systems at mmW and higher frequencies. In systems that have multiple beams, it explores the possibility of using crosscoupled signals to eliminate inter-beam interference (IBI) that affects both transmit and receive beamformers. This assumes that a radio system like 5GNR is aware of interferers in both uplink and downlink (i.e., transmit and receive directions). As the relative bandwidth increases, beam squint, or frequency dependent directivity, limits the wideband IBI cancellation by changing the level and direction of the spatial null towards the interferer. To address the wideband issue the crosscoupled signal approach is further refined, and an analysis of wideband IBI cancellation is also provided.
This thesis also provides a method of stacking uniform linear arrays (ULAs) of various sizes to eliminate sidelobes and produce nulls in the radiated beam pattern. The stacking subarrays approach is designed with predetermined performance constraints to guarantee that the implementation is viable and to enhance sidelobe reduction and null out any known interference.
Moreover, this thesis includes a study on improving the quantization of analog beamformers to take advantage of interference cancellation in multibeam phased arrays. In this thesis, the approaches examined for spatial interference reduction are validated through theoretical analysis, simulations, and some practical assessments utilizing over-the-air (OTA) measurements.
Most interference reduction techniques, both in theory and in practice, require one to control the amplitude of the antenna paths, which results in inefficient use of available power by the power amplifiers, reducing effective isotropic radiated power (EIRP) and, as a result, coverage.
This thesis explores several dynamic beamforming scenarios and strategies for decreasing interference in phased array systems at mmW and higher frequencies. In systems that have multiple beams, it explores the possibility of using crosscoupled signals to eliminate inter-beam interference (IBI) that affects both transmit and receive beamformers. This assumes that a radio system like 5GNR is aware of interferers in both uplink and downlink (i.e., transmit and receive directions). As the relative bandwidth increases, beam squint, or frequency dependent directivity, limits the wideband IBI cancellation by changing the level and direction of the spatial null towards the interferer. To address the wideband issue the crosscoupled signal approach is further refined, and an analysis of wideband IBI cancellation is also provided.
This thesis also provides a method of stacking uniform linear arrays (ULAs) of various sizes to eliminate sidelobes and produce nulls in the radiated beam pattern. The stacking subarrays approach is designed with predetermined performance constraints to guarantee that the implementation is viable and to enhance sidelobe reduction and null out any known interference.
Moreover, this thesis includes a study on improving the quantization of analog beamformers to take advantage of interference cancellation in multibeam phased arrays. In this thesis, the approaches examined for spatial interference reduction are validated through theoretical analysis, simulations, and some practical assessments utilizing over-the-air (OTA) measurements.
Last updated: 17.10.2024