Doctor of Philosophy (PhD)
Electrical and Computer Engineering
First Advisor's Name
John L. Volakis
First Advisor's Committee Title
Second Advisor's Name
Elias A. Alwan
Second Advisor's Committee Title
Third Advisor's Name
Stavros V. Georgakopoulos
Third Advisor's Committee Title
Fourth Advisor's Name
Fourth Advisor's Committee Title
Fifth Advisor's Name
Fifth Advisor's Committee Title
electromagnetics and photonics
Date of Defense
Radio frequency (RF) spectrum congestion is a major challenge for the growing need of wireless bandwidth. Notably, in 2015, the Federal Communications Commission (FCC) auctioned just 65 MHz (a bandwidth smaller than that used for WiFi) for more than $40 billion, indicating the high value of the microwave spectrum. Current radios use one-half of their bandwidth resource for transmission, and the other half for reception. Therefore, by enabling radios to transmit and receive across their entire bandwidth allocation, spectral efficiency is doubled. Concurrently, data rates for wireless links also double. This technology leads to a new class of radios and RF frontends. Current full-duplex techniques resort to either time- or frequency-division duplexing (TDD and FDD respectively) to partition the transmit and receive functions across time and frequency, respectively, to avoid self-interference. But these approaches do not translate to spectral efficiency.
Simultaneous transmit and receive (STAR) radios must isolate the transmitter from the receiver to avoid self-interference (SI). This SI prevents reception and must therefore be cancelled. Self-interference may be cancelled with one or more stages involving the antenna, RF or analog circuits, or digital filters. With this in mind, the antenna stage is the most critical to reduce the SI level and avoid circuit saturation and total system failure.
This dissertation presents techniques for achieving STAR radios. The initial sections of the dissertation provide the general approach of stage to stage cancellation to achieve as much as 100 dB isolation between the receiver and transmitter. The subsequent chapters focus on different antennas to achieve strong transmit/receive isolation. As much as 35 dB isolation is shown using a new spiral antenna array with operation across a 2:1 bandwidth. Also, a new antenna feed is presented showing 42 dB isolation across a 250 MHz bandwidth. Reflections in the presence of a dynamic environment are also considered.
Hovsepian, Alexander, "Novel High Isolation Antennas for Simultaneous Transmit and Receive (STAR) Applications" (2020). FIU Electronic Theses and Dissertations. 4707.
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