Abstract A low loss microwave transmission structure composed of a section of waveguide within which is concentrically placed an array (one or more) of cylindrical sections of dielectric material with relative dielectric constant greater than four, spaced away from the walls by a significant fraction of the radius (at least of the order of 10 percent) and possessing appreciable discontinuities. In the dielectric loaded sections electromagnetic radiation is propagated primarily within the dielectric so that the losses observed are mainly a function of the dielectric material and are, to first order, insensitive to the wall composition or condition. In this most general form the structure can by synthesized as a low loss filter or equalizer. When operated at frequencies at which the unloaded waveguide is below cutoff a high-Q cavity can be formed. A single section cavity of this type has been used to measure the Q of the low loss high dielectric constant dielectrics. A particularly simple and easily adjustable coaxial input and output structure is available which couples strongly to the cylindrically symmetric TM01 mode, all other propagating modes being greatly disfavored.
An electromagnetic wave conducting structure comprising: a. a portion of circular electrically conductive waveguide; b. at least two right circular cylindrical sections of a dielectric material, which are not resonant at a frequency of intended use, concentrically disposed therein; and c. means for launching into said portion of circular waveguide an electromagnetic wave of such frequency that said wave decays essentially exponentially in a radial direction in the space between said cylindrical sections and said waveguide, said means terminating at least one end of said portion of circular waveguide characterized in that the said cylinders are spaced away from the wall of the said waveguide by at least of the order of 10 percent of the waveguide radius, that the relative dielectric constants of the said cylinders are at least of the order of four and that the structure contains discontinuities of magnitude such that the product of each dielectric cylinder diameter and the square root of its dielectric constant changes from one section to the next by more than 10 percent within a distance equal to one quarter of the cylinder diameter.
Claim 2
Dependent Claim
183 words
An electromagnetic wave conducting structure comprising: a. a portion of circular electrically conductive waveguide; b. at least two right circular cylindrical sections of a dielectric material, which are not resonant at a frequency of intended use, concentrically disposed therein; and c. means for launching into said portion of circular waveguide an electromagnetic wave of such frequency that said wave decays essentially exponentially in a radial direction in the space between said cylindrical sections and said waveguide, said means terminating at least one end of said portion of circular waveguide characterized in that the said cylinders are spaced away from the wall of the said waveguide by at least of the order of 10 percent of the waveguide radius, that the relative dielectric constants of the said cylinders are at least of the order of four and that the structure contains discontinuities of magnitude such that the product of each dielectric cylinder diameter and the square root of its dielectric constant changes from one section to the next by more than 10 percent within a distance equal to one quarter of the cylinder diameter.
Claim 3
Dependent Claim
38 words
A device of claim 1 in which said means for launching is a structure comprising a coaxial probe jointed to the center conductor of a coaxial transmission line whose outer conductor is electrically joined to the said waveguide.
Claim 4
Dependent Claim
21 words
A device of claim 1 including at least one section cut off in the direction of propagation for the mode employed.
Claim 5
Dependent Claim
24 words
A device of claim 2 wherein the said outer conductor is joined to the said waveguide wall by means of a flexible metallic bellows.
Claim 6
Dependent Claim
32 words
A device of claim 1 wherein at least one of said cylindrical sections is terminated, at least at one end, by a tapered transformer section comprising a tapered section of dielectric material.
Claim 7
Dependent Claim
15 words
A device of claim 1 in which said electromagnetic wave is in the TM01 mode.