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Access Type
WSU Access
Date of Award
January 2022
Degree Type
Dissertation
Degree Name
Ph.D.
Department
Electrical and Computer Engineering
First Advisor
Mohammad Alhawari
Second Advisor
Dimitrios L. Sounas
Abstract
Circulators are nonreciprocal devices used in RF communication systems. They are typically designed using ferromagnetic material and used in larger systems such as radars and satellites. They allow the use of the full bandwidth for both TX and RX while providing isolation between the two paths. With increasing demand in connectivity, consumer wireless communication systems are scaling at a rapid rate to align with demand. Many wireless systems employ either Frequency-Division Duplexing (FDD) or Time-Division Duplexing (TDD), however, these techniques require double the bandwidth to achieve a given data rate. FDD requires separate frequency bands while TDD only transmits 50\% of the time in each direction. These approaches might not be feasible for larger data rates and different techniques must be investigated. Employing circulators in these wireless systems will allow the networks to increase speeds and not necessarily require using double the bandwidth. However, traditional circulator designs using ferromagnetic material do not scale to incorporate in IC level designs. Recently, magnetless type circulators have quickly gained traction as a feasible solution.
Different type of magnetless circulators have been investigated over the past several years, but all have utilized external modulation sources with complex phase-shifter networks to achieve given phase requirements. Our goal is to introduce a new family of magnetless circulators that utilize localized oscillators at each modulated resonator of the circuit to both eliminate the use of external sources and phase-shifters. This type of ciruclator is designed as an autonomous block that can be incorporated as an independent component in a communication system.
We have validated this approach by designing the autonomous circulator block on a PCB evaluating electrical characteristics for both a newly introduced common/differential topology and a fully differential circulator. Both designs yielded great results affirming the advantages of our approach. Generating the required modulation signals locally, reduces the complexity of the design making it advantageous in efficiency, cost and form factor. Our common/differential topology also provides another advantage of natural isolation reducing the leakage of the modulation signals to the RF ports. This work demonstrated the feasibility of a circulator design as an independent, CMOS compatible, block that can be integrated independently in different communication systems.
Recommended Citation
Kadry, Haysam M., "Autonomous, Cmos-Compatible, Spatiotemporally Modulated Magnetless Circulators For Next Generation Full-Duplex Communication Systems" (2022). Wayne State University Dissertations. 3758.
https://digitalcommons.wayne.edu/oa_dissertations/3758