Open Resonators with Conducting Cylindrical Inserts. 1. Two-Dimensional Model

Abstract

We present the results of computer simulation of the properties of modes in a two-dimensional open resonator with a conducting cylindrical insert. An increase in the diffraction Q-factor of the fundamental mode by 2-3 orders of magnitude due to the conducting cylindrical insert is found and studied. The prospects of using this phenomenon for controlling the spectrum, frequencies, and Q-factors of excited modes are discussed. The tunability of the open resonator with a conducting cylindrical insert for one (fundamental) mode in a wide frequency range is shown.

An Open Resonance Cell for Millimeter Wave Dielectrometer Applications

“…Another reason is a structural change of the resonance field that shrinks toward the OR axis (the log Q second maximum at 2aq/L ≈ 1.0 ÷ 1.1) [9]. This effect is responsible for that the dielectric loss measurement of the specimen can run into difficulties consisting in that the Q comparison of the empty and rod-loaded ORC structures can yield a negative-valued dielectric loss, which is physically untrue.…”

Open Resonators with Conducting Cylindrical Inserts. 2. Resonators with Finite-Length Mirrors

“…One of the most efficient methods for controlling the spectrum and Q-factors of modes excited in open resonant structures is to insert a single inhomogeneity or diffraction arrays composed of such inhomogeneities in the open resonators (ORs). In the first part [2] of this work, using the numerical simulation, we studied the effect of a resonant increase in the diffraction Q-factor of TEM 00q modes in a two-dimensional OR with a cylindrical conducting insert. Physically, this effect is caused by a change in the field structure inside the resonator with a conducting insert leading to a decrease in the diffraction losses of TEM 00q modes in ORs with small mirror apertures.…”

“…It is shown in [2] that placing a cylindrical conducting insert with a resonant diameter leads to a decrease in the radiation losses caused by the leakage of the mode energy along the x axis, i.e., to an increase in Q Dx in Eq. (1).…”

“…To reveal an increase in the diffraction Q-factor Q Dx of modes during the experiment in the three-dimensional analog of an OR with a conducting insert, we should choose such geometric parameters of the mirrors that allow us to overcome the masking effect of decreasing the total Q-factor Q Σ of modes when passing from the two-dimensional model of an OR to the resonator with finite-length mirrors. Since the cylindrical-mirror parameters R c and 2ϕ 0 , the intermirror distance 2l, and the resonant diameter 2a of the conducting insert are chosen on the basis of the numerical results of [2], we should properly choose the cylindrical-mirror length 2b along the y axis for the three-dimensional analog of an OR.…”

“…1a) for the experimental verification of an increase in the diffraction Q-factor of modes due to a conducting cylindrical insert in the 10-mm wavelength range. It was shown in [2], that in the chosen wavelength range, the effect of a resonant increase in the diffraction Q-factor due to the conducting cylindrical insert is the most pronounced for the TEM 005 mode for the resonator-mirror parameters R c = 23 mm, l/R c = 0.57, and 2ϕ 0 = 80 • . In this case, the diffraction Q-factors Q Dx of the fundamental TEM 005 mode and the neighboring TEM 104 and TEM 204 modes amount to Q 005 = 3500, Q 104 = 570, and Q 204 = 390, respectively, i.e., the efficient leakage of the higher-order modes from this OR is observed.…”