LAUSR

Author(s): Biedka, Mathew Michael | Advisor(s): Wang, Yuanxun | Abstract: As more and more people and devices become connected across the globe, the strain on the RF spectrum that they use to communicate increases. Current methods of communication typically separate transmit and receive information into frequency channels or time slots which leads to inefficiency due to the presence of guard bands or guard intervals. Wireless communication systems of the future will need to be able to transmit and receive electrical signals at the same time and over the same frequency. This is known as Full Duplex communication, which is achievable through the use of a circulator. Typical circulators are able to separate transmit and receive paths to achieve Full Duplex communication through the biasing of magnetic materials. They provide low loss from port to port as well as high power handling that is needed for the transmit path. These circulators are cavities that support non-reciprocal resonant modes which lack wideband performance. Also, their physical size is dependent upon the wavelength of operation, which makes them difficult to integrate with modern IC technology. As a solution to these challenges, the Sequentially-Switched Delay Lines (SSDL) Circulator is proposed. The switches are turned on and off sequentially to distribute and route the propagating electromagnetic waves, allowing for simultaneous transmission and reception of signals through the device. There is no theoretical limit to the operating frequency range of the SSDL circulator, as the only requirement for operation is the synchronization of the switch timing and propagation delay. Experimental results for the original SSDL architecture composed of five RF switches and six transmission delay lines (six-line SSDL Circulator), along with a simplified design which preserves the nonreciprocal behavior (two-line SSDL Circulator) are reported. Preliminary results for the six-line SSDL Circulator using commercially available parts demonstrate isolation between the transmit and receive paths greater than 40dB from 200 KHz to 200 MHz. In addition, experimental results of both SSDL Circulator architectures on a GaN MMIC achieve full duplex behavior from DC up to 1 GHz.