A novel highly accurate synthetic technique for determination of the dispersive characteristics in periodic slow wave circuits

Guo, H.; Carmel, Y.; Lou, W. R.; Chen, L.; Rodgers, J.; Abe, David K.; Bromborsky, A.; Destler, W.W.; Granatstein, V.L.

doi:10.1109/22.168767

Cited by 65 publications

(51 citation statements)

References 6 publications

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“…Similar agreement is observed for both N = 2 and N = 8 and not shown here for the sake of brevity. Recall that a conventional periodic structure of N periods exhibits discrete resonant frequencies with phase shifts per period spaced between 0 and  pertaining to a sole excited mode [35]. This is depicted from the resonances in Fig.…”

Section: B Reflection Measurementsmentioning

confidence: 99%

“…Therefore, the most unique DBE characteristic of a periodic waveguide is its respective dispersion diagram which portrays how the phase changes with frequency over the passband of the structure. Although different approaches exist to estimate the dispersion diagram of a waveguide from a measurement on the finite length waveguide (see [11] for example), we use a synthetic method [35] based on the measurement of the resonance frequencies of the cavity formed in Fig. 1.…”

Section: B Reflection Measurementsmentioning

confidence: 99%

“…with 's m a coefficients are geometry-dependent and determined using the resonance frequencies of the structure (see equations (2)- (9) in [35]), and here the Bloch wavenumber is real-valued within the range 0…”

Section: B Reflection Measurementsmentioning

confidence: 99%

“…The dispersion is then approximated by taking into account the number of observed resonances in the finite-length structure, and the number of resonance is denoted by M. Thus the dispersion relation is approximately equivalent to [35] …”

Section: B Reflection Measurementsmentioning

confidence: 99%

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Experimental Demonstration of Degenerate Band Edge in Metallic Periodically Loaded Circular Waveguide

Othman¹,

Pan

Atmatzakis

et al. 2017

IEEE Trans. Microwave Theory Techn.

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Abstract-We experimentally demonstrate for the first time the degenerate band edge (DBE) condition, namely the degeneracy of four Bloch modes, in loaded circular metallic waveguides. The four modes forming the DBE represent a degeneracy of fourth order occurring in a periodic structure where four Bloch modes, two propagating and two evanescent, coalesce. It leads to a very flat wavenumber-frequency dispersion relation, and the finitelength structure's quality factor scales as N 5 where N is the number of unit cells. The proposed waveguide in which DBE is observed here is designed by periodically loading a circular waveguide with misaligned elliptical metallic rings, supported by a low-index dielectric. We validate the existence of the DBE in such structure using measurements and we report good agreement between full-wave simulation and the measured response of the waveguide near the DBE frequency; taking into account metallic losses. We correlate our finding to theoretical and simulation results utilizing various techniques including dispersion synthesis, as well as observing how quality factor and group delay scale as the structure length increases. Moreover, the reported geometry is only an example of metallic waveguide with DBE: DBE and its characteristics can also be designed in many other kinds of waveguides and various applications can be contemplated as high microwave generation in amplifiers and oscillators based on an electron beam interaction or solid state devices, pulse compressors and microwave sensors.Index Terms-Degenerate band edge (DBE), slow-wave structures, cavity resonators.

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Section: B Reflection Measurementsmentioning

confidence: 99%

Section: B Reflection Measurementsmentioning

confidence: 99%

Section: B Reflection Measurementsmentioning

confidence: 99%

Section: B Reflection Measurementsmentioning

confidence: 99%

See 2 more Smart Citations

Experimental Demonstration of Degenerate Band Edge in Metallic Periodically Loaded Circular Waveguide

Othman¹,

Pan

Atmatzakis

et al. 2017

IEEE Trans. Microwave Theory Techn.

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“…In the simple classical description, the BWO consists of a spatially periodic waveguide into which a high-current electron beam (confined by a strong magnetic field) is injected to drive and interact with azimuthally symmetric transverse magnetic (TM) modes, as just these modes are able to perturb the axial velocity and electron density on rectilinear beams. In many works [2][3][4][5][6][7][8] the periodic structure, in general a sinusoidally rippled cylindrical guide, is merely displayed in its final configuration, with no account as to how the geometry of the structure has been synthesized aiming at its particular application. Adressing this basic question, here we present design tools for the synthesis of sinusoidal profiles from the technical goals for the BWO, namely, the operating frequency and the beam energy.…”

Section: Introductionmentioning

confidence: 99%

The sinusoid as the longitudinal profile in backward-wave oscillators of large cross sectional area

Neto¹,

Barroso²

2004

Braz. J. Phys.

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High-power generation in backward-wave oscillators (BWO) of large section requires that the beam electrons flowing close to the corrugated wall interact efficiently with surface waves supported by a periodic structure. Such waves are described by the superposition of slow-wave space harmonics of the operating mode. The present paper reports on design tools for BWOs operating in symmetric TM modes since these modes are able to perturb the axial velocity and electron density on rectilinear beams confined by an external magnetic field in slow-wave systems. Here we investigate whether a cylindrical guide with sinusoidally rippled wall can provide strong coupling between the guide surface waves and mildly relativistic (∼ 500 keV) electron beams in the 8-9 GHz frequency range for BWOs of large diameter (D ∼ 3λ). For this purpose, the characteristic equation of a sinusoidally corrugated structure is derived on the basis of the Rayleigh-Fourier method, whereby the field solution is represented by a single expansion of TM eigenmodes. From the dispersion diagrams thus obtained we infer the appropriate periodic length and ripple amplitude of the guiding structure that optimize the beam-wave interaction.

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Dispersion Engineering for Slow‐Wave Structure Design

Chipengo

Nahar

Volakis

et al. 2021

High Power Microwave Sources and Technologies Using Metamaterials

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A novel highly accurate synthetic technique for determination of the dispersive characteristics in periodic slow wave circuits

Cited by 65 publications

References 6 publications

Experimental Demonstration of Degenerate Band Edge in Metallic Periodically Loaded Circular Waveguide

Experimental Demonstration of Degenerate Band Edge in Metallic Periodically Loaded Circular Waveguide

The sinusoid as the longitudinal profile in backward-wave oscillators of large cross sectional area

Dispersion Engineering for Slow‐Wave Structure Design

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