Microwave open resonator techniques—part II: applications

Abstract:

The accurate modelling of dielectric and impedance features [1, 2] is an essential need for the efficient design of microstrip circuits and antennas. The increasing demand for miniaturization and high-frequency operation strongly imposes the accurate characterization of low-loss thin dielectric surfaces [12, 14], both in the form of simple laminated substrates [6, 9, 19, 23], as well as in more complex configurations of microstrip grids to be used for reflectarray/transmitarray structures [3, 21]. Various microwave techniques have been introduced in literature to characterize the electrical properties of materials. They include open-ended waveguide/coaxial probe methods [18], free-space techniques [16], stripline [20], transmission/reflection [4] and resonant [22] procedures, all having specific advantages and constraints. Among them, open resonator methods [10, 11, 13, 15, 17, 25] give the most powerful tool to accurately retrieve the equivalent impedance properties of low-loss thin dielectric surfaces. In the standard resonator approach [25], approximate empirical formulas are adopted to obtain the surface impedance characterization from the knowledge of measured resonance parameters, such as the frequency shift and the cavity quality factor. Information from different sample thicknesses and/or positioning are generally adopted to increase the accuracy in the surface parameters extraction, which is performed in terms of a transcendental equation having multiple roots [11]. All existing papers on open resonator methods inherit the approach proposed in [25], thus assuming an ideal open cavity and neglecting the excitation of higher-order modes, which …

Año de publicación:

2012

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Fuente:

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