Exciting Traveling Waves in High Q Structures Using Microstrip

A C Fowler, M E Tobar, CR Locke, E N Ivanov, JG Hartnett, J Anstie, D Cros

Abstract:	Exciting traveling waves in high-Q resonant structures can simplify low noise oscillator designs [1], [2], [3] and also as applications for newly proposed Lorentz Invariance tests [4]. In this work we use microstrip probes to excite traveling waves in a sapphire dielectric resonator. Previous work has indicated that matching microstrip probes to a sapphire resonator can be a difficult requirement [5]. A model has been developed, which takes into account leakage of the microstrip line in the reverse direction to which we excite the traveling wave. From such a model we can define the Standing Wave Ratio (SWR) from the amount of forward and reverse traveling wave in the resonator. Ideally for a perfect traveling wave the SWR = 0, and for a standing wave the SWR = 1. By comparing the model with experiment we find that we can excite a traveling wave with an SWR of 0.35 and an unloaded Q-factor of 150,000 in a WGH12,0,2 mode at 9.997 GHz, in a sapphire of 5 cm diameter and 3 cm height. From the model, we also propose new oscillator designs for low noise applications.
Published in:	Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting August 29 - 31, 2005 Vancouver, Canada
Pages:	512 - 516
Cite this article:	Fowler, A C, Tobar, M E, Locke, CR, Ivanov, E N, Hartnett, JG, Anstie, J, Cros, D, "Exciting Traveling Waves in High Q Structures Using Microstrip," Proceedings of the 37th Annual Precise Time and Time Interval Systems and Applications Meeting, Vancouver, Canada, August 2005, pp. 512-516.
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