An Ultra-Low Loss Radio Frequency Beamforming Technique for Power-Constrainted Phased Array Applications

Matthew Anderson

EECS Department
University of California, Berkeley
Technical Report No. UCB/EECS-2024-194
December 1, 2024

http://www2.eecs.berkeley.edu/Pubs/TechRpts/2024/EECS-2024-194.pdf

Phased arrays have become increasingly important as wireless networks and sensors move to higher frequencies in an effort to alleviate overcrowding, increase bandwidth and improve spatial resolution. These arrays provide significant benefits by allowing the nodes within a wireless network to quickly steer their high-gain beams, i.e. beamforming, to maximize signal strength and reduce overall interference.

However, current methods of beamforming require significant power, making them impractical for power-constrained applications. This is, in part, because the passive radio frequency (RF) structures used for phased shifting and summation in these beamformers are quite lossy and require compensation with power-hungry amplifiers. The additional power-intensive RF amplification, along with the large number of antenna elements, means modern phased arrays often consume significant amounts of power and produce large amounts of heat. Both the power consumption and thermal load create challenges for mobile and low-power applications.

To address these challenges, this work presents a fully-passive method of beamforming with better than state-of-the-art passive loss. This technique utilizes: (1) balanced impedance phase shifters, which take advantage of array symmetry to reduce the number of lossy passive components, and (2) transmission-line transformers built into the high-Q PCB antenna feed traces to enable low-loss combining and impedance transformation. The theoretical operation of the proposed fully-passive beamformer is detailed in this dissertation, with special emphasis on estimation of key performance metrics using circuit theory. To validate the theory, we present the design and test results from a prototype 4-channel, 12~GHz, RF beamforming integrated circuit (IC) utilizing the proposed technique.

Advisor: Jan M. Rabaey and Ali Niknejad

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BibTeX citation:

@phdthesis{Anderson:EECS-2024-194,
    Author = {Anderson, Matthew},
    Title = {An Ultra-Low Loss Radio Frequency Beamforming Technique for Power-Constrainted Phased Array Applications},
    School = {EECS Department, University of California, Berkeley},
    Year = {2024},
    Month = {Dec},
    URL = {http://www2.eecs.berkeley.edu/Pubs/TechRpts/2024/EECS-2024-194.html},
    Number = {UCB/EECS-2024-194},
    Abstract = {Phased arrays have become increasingly important as wireless networks and sensors move to higher frequencies in an effort to alleviate overcrowding, increase bandwidth and improve spatial resolution. These arrays provide significant benefits by allowing the nodes within a wireless network to quickly steer their high-gain beams, i.e. beamforming, to maximize signal strength and reduce overall interference. 

However, current methods of beamforming require significant power, making them impractical for power-constrained applications. This is, in part, because the passive radio frequency (RF) structures used for phased shifting and summation in these beamformers are quite lossy and require compensation with power-hungry amplifiers. The additional power-intensive RF amplification, along with the large number of antenna elements, means modern phased arrays often consume significant amounts of power and produce large amounts of heat. Both the power consumption and thermal load create challenges for mobile and low-power applications.

To address these challenges, this work presents a fully-passive method of beamforming with better than state-of-the-art passive loss. This technique utilizes: (1) balanced impedance phase shifters, which take advantage of array symmetry to reduce the number of lossy passive components, and (2) transmission-line transformers built into the high-Q PCB antenna feed traces to enable low-loss combining and impedance transformation. The theoretical operation of the proposed fully-passive beamformer is detailed in this dissertation, with special emphasis on estimation of key performance metrics using circuit theory. To validate the theory, we present the design and test results from a prototype 4-channel, 12~GHz, RF beamforming integrated circuit (IC) utilizing the proposed technique.}
}

EndNote citation:

%0 Thesis
%A Anderson, Matthew
%T An Ultra-Low Loss Radio Frequency Beamforming Technique for Power-Constrainted Phased Array Applications
%I EECS Department, University of California, Berkeley
%D 2024
%8 December 1
%@ UCB/EECS-2024-194
%U http://www2.eecs.berkeley.edu/Pubs/TechRpts/2024/EECS-2024-194.html
%F Anderson:EECS-2024-194