Higher Order Modes in Square Coaxial Lines

Gruner, L.

doi:10.1109/tmtt.1983.1131588

Cited by 24 publications

(14 citation statements)

References 4 publications

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“…When higher modes are present, these lead to a dispersive transmission line, so for most applications it is desired to propagate only a TEM mode. Information to calculate the presence of non-TEM modes in square coaxial lines are given in [6]. The impedance of the square coaxial line in Fig.…”

Section: Design Of Square-cross-section Cablesmentioning

confidence: 99%

Air-filled square coaxial transmission line and its use in microwave filters

Llamas-Garro

Lancaster

Hall

2005

IEE Proc., Microw. Antennas Propag.

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A suspended coaxial transmission line with an air propagation medium is presented. The transmission line is made only of metal, thereby avoiding dielectric and radiation losses. Shortcircuit stubs suspend the centre conductor of the coaxial structure which is used in the design of two dual-mode narrowband microwave filters. Stacked layers of copper sheets are used to form the square coaxial transmission line, which has low loss and low dispersion.

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Section: Design Of Square-cross-section Cablesmentioning

confidence: 99%

Air-filled square coaxial transmission line and its use in microwave filters

Llamas-Garro

Lancaster

Hall

2005

IEE Proc., Microw. Antennas Propag.

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“…Although analytic solutions for the fundamental properties (for example, the characteristic impedance) of rectacoax do exist, they are in the form of infinite-series or integral solutions that are not amenable to simple design rules [5]. Therefore, fast full-wave techniques (such as transmission-line matrix) have been developed, particularly for designing junctions and other discontinuities [6 -8].…”

Section: Introductionmentioning

confidence: 99%

Characteristics of microfabricated rectangular coax in the Ka band

Brown

Cohen²,

Bang³

et al. 2004

Micro & Optical Tech Letters

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Miniature rectangular coaxial transmission line (with a 300 × 300 μm outer conductor) is simulated, fabricated, and tested up to the Ka band. It is made by the electrochemical fabrication (EFAB™) of nickel such that the center conductor is supported primarily by ≈λ/4 stubs that also establish a resonant passband. The minimum insertion loss of a 1.67‐cm‐long test structure is found to be 1.74 dB at the passband center of 29 GHz. This is within 0.57 dB of the lowest insertion loss predicted by full‐wave numerical simulations, indicative of the high precision and smooth surface morphology of the EFAB process. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 40: 365–368, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.11383

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“…A simple Chebycheff response is chosen. In order to minimise loss, it is important to have a large cable cross section; however, there comes a point where nonTEM modes begin to propagate [12,13], and this therefore limits the size. The particular filter demonstrated in this paper has a centre frequency of 9 GHz with a 0.01-dB passband ripple, and a 70% fractional bandwidth.…”

Section: Introductionmentioning

confidence: 99%

A low‐loss wideband suspended coaxial transmission line

Llamas-Garro

Lancaster

Hall

2004

Micro & Optical Tech Letters

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of the core and cladding are very similar" [6]. As observed from Figure 3, this is only true for photonic-crystal fiber with small hole diameters. The validity of this approach may therefore become questionable for larger hole diameters.More accurate results may be obtained by using numerical differentiation to investigate the dispersion properties of photoniccrystal fibers. Using values of n 1 obtained by the Sellmeier equation and corresponding values of n 2eff (Fig. 3), the values of propagation constant ␤ are calculated for different wavelengths using step-index fiber theory. The values of (␤⌳) against (k⌳) are modeled using a piecewise polynomial interpolation of order 3. The normalized GVD in Eq. (3) is then obtained by differentiating the interpolating polynomials. This procedure includes the effect of dispersion in silica and does not need the addition of material dispersion. Since no other approximations are used, the validity of results obtained in this way is only limited by the degree of accuracy to which the values of ␤ have been computed. Figure 5 shows the calculated results using the two different approaches. The plots are given for the range of wavelength of interest in current optical-fiber communication systems. Moreover, outside this range of wavelength, the material (silica) dispersion predominates over waveguide dispersion.It may be observed that the normalized GVD calculated by both procedures agree for small hole diameter, but not for larger holes. This confirms the fact that the separation of normalized GVD into the two components, as in Eq. (4), is only valid for a limited range of hole diameters. The cause can be seen by examining the variation of the refractive index of silica and that of the effective refractive index with wavelength shown in Figure 3. For small hole diameter, the variation of effective refractive index with wavelength closely follows that of the refractive index of silica. However, for larger holes, the variation of effective index with wavelength diverts from that of the refractive index of silica, thus violating the principle upon which the separation is based [6]. CONCLUSIONMost of the reported research on photonic-crystal fibers uses a nominal refractive index of silica, such as the "vector methods" in [3, 7]. However, we note that in [7] material dispersion was included by using an iterative algorithm and the standard Sellmeier equation for calculating dispersion characteristics of a photoniccrystal fiber.In this paper, the separation of normalized GVD was shown to be valid only for small hole diameters, in which case the variation of the effective index closely follows that of the wavelengthdependent refractive index of silica. It was further demonstrated that, for a more accurate analysis encompassing a much wider range of hole diameters, the wavelength-dependent refractive index of silica needs to be taken into account in all calculations.

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Higher Order Modes in Square Coaxial Lines

Cited by 24 publications

References 4 publications

Air-filled square coaxial transmission line and its use in microwave filters

Air-filled square coaxial transmission line and its use in microwave filters

Characteristics of microfabricated rectangular coax in the Ka band

A low‐loss wideband suspended coaxial transmission line

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