Characteristics of some ferrous and non-ferrous waveguides at 27 Gc/s

Allison, J.; Benson, F.A.; Seaman, Mark

doi:10.1049/pi-b-1.1957.0214

Cited by 5 publications

(6 citation statements)

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“…The approach is similar to the one adopted in the present paper, i.e., to estimate permeability from power attenuation, which was then argued to have good accuracy. [17] extended these results to 27 GHz and showed amplitudes of resistive µ r up to 84 for mild steel.…”

Section: B Magnetic Permeabilitymentioning

confidence: 73%

“…These values refer to bulk forms and are typically obtained at DC. Results at higher frequency, in particular in the microwave range are available but require a careful interpretation, since the contributions of finite electrical conductivity and ferromagnetic behavior cannot be measured separately [17], [24], thus requiring assumptions. Results from non-magnetic metals suggest that the bulk conductivity is practically constant [24], with transitions rather expected at near-optical frequencies.…”

Section: Electrical Conductivitymentioning

confidence: 99%

“…which coincides with the resistive relative permeability [17]. Applying similar steps, the skin depth δ m of a magnetic conductor should be updated as…”

Section: Dissipation In Bulk Ferrous Boundariesmentioning

confidence: 99%

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Power Dissipation in Reverberation Chamber Metallic Surfaces Based on Ferrous Materials

Cozza

Monsef

2019

IEEE Trans. Electromagn. Compat.

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Models predicting the composite quality factor (QF) of a reverberation chamber (RC) consider, among several potential contributors, dissipation in its metallic boundaries. The related partial quality factor, Qw, is of fundamental importance, as it controls the asymptotic high-frequency behavior of an RC and, ultimately, its ability to generate high-intensity fields. Yet, the current model has been known to overestimate in certain cases the composite QF by up to several dB. This paper provides insight into the causes of these disagreements by introducing generalized models of dissipation in ferrous materials found in RCs, by first acknowledging that their magnetic permeabilities are complex quantities, which is shown to theoretically boost dissipation well beyond the GHz range. A more general dissipation model is presented, taking into account the layered nature of steel plates. Among its predictions, confirmed by experiments, are extra losses from steel surfaces in the lower frequency range and the linear increase in Qw over the GHz range, as opposed to a squareroot dependence expected for homogeneous bulk metals. Metallic coating layers, originally introduced to protect steel plates, have therefore a more fundamental role to play, controlling dissipation levels by reducing interactions with ferrous materials and should therefore be designed accordingly.

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Section: B Magnetic Permeabilitymentioning

confidence: 73%

Section: Electrical Conductivitymentioning

confidence: 99%

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Power Dissipation in Reverberation Chamber Metallic Surfaces Based on Ferrous Materials

Cozza

Monsef

2019

IEEE Trans. Electromagn. Compat.

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“…1 can be rearranged in the form 14 (5) where R s is the surface resistivity of the waveguide material in ohms per square.…”

Section: Discussionmentioning

confidence: 99%

“…4 Measurements of the attenuations produced by various rectangular waveguides have also been made at a frequency of 27 Gc/s. 5 The present paper describes investigations carried out to determine the losses in rectangular waveguides of several materials at frequencies of 35, 70 and 140 Gc/s. The internal surface finishes of many waveguide samples have been observed, and the effects of annealing some tubes in a hydrogen atmosphere and acid-etching the internal surfaces have been determined.…”

Section: Introductionmentioning

confidence: 99%

Rectangular-waveguide attenuation at millimetre wavelengths

Benson

Steven

1963

Proc. Inst. Electr. Eng. UK

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Measurements of the attenuations produced by air-filled rectangular waveguides of various materials have been made at frequencies of 35, 70 and 140Gc/s. Some effects of corrosion, annealing waveguides in a hydrogen atmosphere, acid etching of internal surfaces and electroplating have been determined. Internal surface finishes of many waveguide samples have been observed and d.c. resistivities of the materials have been measured.Measured losses are all well in excess of the theoretical values as predicted by formulae for perfectly smooth walls (e.g. up to 2-5 times in the case of copper at frequencies of 70 and 140Gc/s). The discrepancies between calculated and experimental values increase with frequency and cannot be wholly accounted for at millimetre wavelengths by surface roughness. Attenuations can be reduced considerably by annealing or etching waveguide surfaces.Losses in waveguides increase after exposure to the atmosphere, and the corrosion characteristics of tellurium-copper, which has been recommended 13 for millimetre wavelengths, appear to be no better than those of pure copper or standard silver.Electroplating of certain waveguide components for millimetre wavelengths may be worth while.List of principal symbols a -short internal dimension of waveguide, m b = long internal dimension of waveguide, m r = voltage standing-wave ratio (measured as a quantity greater than unity) w = distance between two points of equal field strength on either side of a minimum of the standing wave, m (at the w points the field strength is k times that at the minimum) K TX , K T2 , K p = surface-roughness factors in attenuation equations a = attenuation coefficient of the waveguide, nepers/m (unless otherwise stated) € = permittivity of the dielectric (in this case air) inside the waveguide, F/m fx = permeability of the dielectric inside the waveguide, H/m H R = relative 'resistive' permeability of waveguide wall metal p = resistivity of the waveguide wall metal, Q-m X e = free-space wavelength, m A cr = critical guide wavelength, m X g = guide wavelength, m

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Understanding the Apparently Poor Conductivity of Galvanized Steel Plates

Cozza¹

2021

IEEE Access

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This paper investigates the physical reasons for the apparently poor conductivity of galvanized steel plates (GSP), which has not yet received a proper explanation. Apparent conductivities as low as 0.1 MS/m were reported in the past, which are incongruously low compared to the DC conductivity of steels (4 to 8 MS/m), or zinc (16.7 MS/m), the most common coating agent used against corrosion in steel products. A comprehensive review of results from metallurgy and materials science is presented, providing insights about the multi-layered structure of zinc-based coatings. These are found to be made of a limited set of intermetallic zinc-iron compounds each characterized by a steeply decreasing conductivity as their iron percentage increases. Depending on the galvanization process the relative thickness of these layers can vary widely, explaining the seemingly random apparent conductivity of GSP. Theoretical modeling of these structures shows that their apparent conductivity scales linearly with the frequency, suggesting that it can be far lower than acknowledged so far. An extensive analysis of power-dissipation data from the literature of GSP-based reverberation chambers confirms these predictions, with multiple instances of apparent conductivities as low as 10 kS/m.The conclusion is not that GSP are hopelessly poorly conductive, but rather that care should be taken in selecting the right coating technology, not only based on corrosion protection and minimizing costs, but also in view of its impact on GSP conductivity.

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Characteristics of some ferrous and non-ferrous waveguides at 27 Gc/s

Cited by 5 publications

References 6 publications

Power Dissipation in Reverberation Chamber Metallic Surfaces Based on Ferrous Materials

Power Dissipation in Reverberation Chamber Metallic Surfaces Based on Ferrous Materials

Rectangular-waveguide attenuation at millimetre wavelengths

Understanding the Apparently Poor Conductivity of Galvanized Steel Plates

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