Date of Award
Doctor of Philosophy (PhD)
Dejan S. Filipović
W Neill Kefauver
Most modern wireless communication systems operate either at different times or frequencies to avoid self-interferences. With these duplexing techniques, more resources are required due to the increased demand for higher data rate. Therefore, alternative solutions not involving more use of the time or frequency spectrum are needed. One of the possible solutions that has been recently gaining increased interest is often referred to as co-channel simultaneous transmit and receive (C-STAR). C-STAR is considered by many as a key enabling technology for the next-generation wireless networks operating in spectrum congested environments. C-STAR allows transmitting (TX) and receiving (RX) at the same time and over the same frequency channel which may result in significant improvements in throughput and spectral efficiency. The chief challenge associated with these C-STAR systems is the required very high TX/RX isolation (110-140 dB) to suppress the self-interference. To obtain the necessary isolation over any bandwidth, a C-STAR transceiver is typically divided into several self-interference cancellation stages. Specifically these include antenna, analog, and digital layers. Clearly, the antenna array layer plays an important role in maximizing the overall system isolation since ~30-50% of the required isolation is achieved with a well-designed C-STAR antenna subsystem, then the overall system becomes feasible. In this Ph.D. thesis, several novel wideband co-polarized circulator and circulator-less monostatic antenna and array designs are presented. Developed theoretical concepts are validated with full-wave simulations and measurements. The monostatic C-STAR apertures utilizing multi-arm spiral antennas are first demonstrated where a set of arms is used for transmitting and the other set for receiving. Then, different novel omnidirectional and broadside C-STAR arrays utilizing closely-spaced spiral, monocone, or discone antennas are introduced. Phase mode orthogonality principle, antenna orientation, and beam-former cancellation are all combined to achieve the desired performance. All proposed C-STAR configurations have theoretically infinite isolation between TX and RX ports. Practically, the achieved isolation is limited by the electrical asymmetries of the used components. Overall, consistent wideband operation, high measured isolation, and good far-field performance are achieved for all proposed C-STAR antenna array sub-systems without taking advantages of any time-, frequency-, polarization-, pattern-, antenna-, and spatial-multiplexing.
Etellisi, Ehab Abdalla, "Wideband Monostatic Co-Channel Simultaneous Transmit and Receive (C-STAR) Antenna and Array Systems" (2018). Electrical, Computer & Energy Engineering Graduate Theses & Dissertations. 161.