Dispersion Characteristics of a Rectangular Helix Slow-Wave Structure
TL;DR: In this article, a special type of helical slow-wave structure encompassing a rectangular geometry is investigated, and the slowwave characteristics are studied taking into account the anisotropic conducting helix.
Abstract: A special type of helical slow-wave structure encompassing a rectangular geometry is investigated in this paper, and the slow-wave characteristics are studied taking into account the anisotropically conducting helix. By using the electromagnetic integral equations at the boundaries, the dispersion equation and the interaction impedance of transverse antisymmetric modes in this structure are derived. Moreover, the obtained complex dispersion equation is numerically calculated. The calculation results by our theory agree well with the results obtained by the 3-D EM simulation software HFSS. The numerical results reveal that the phase velocity decreases and interaction impedance increases at higher frequencies by flattening (increasing the aspect ratio of) the rectangular helix structure. In addition, a comparison of slow-wave characteristics of this structure with a conventional round helix is made.
Citations
More filters
TL;DR: In this article, a V-shaped microstrip meander-line slow-wave structure was proposed for use in a lowvoltage high-efficiency widebandwidth miniature millimeter-wave traveling-wave tube (TWT).
Abstract: In this paper, a novel V-shaped microstrip meander-line slow-wave structure (SWS) is proposed for use in a low-voltage high-efficiency wide-bandwidth miniature millimeter-wave traveling-wave tube (TWT). The electromagnetic characteristics and the interaction between the sheet electron beam and slow wave in this SWS are obtained by utilizing the CST Microwave Studio and Particle Studio codes, respectively. From our calculations, it is predicted that, at a beam voltage of 3.7 kV and a beam current of 100 mA, an output power greater than 30 W can be obtained ranging from 75 to 100 GHz, and this V-shaped microstrip meander-line TWT will be helpful for a W-band millimeter-wave power module.
93 citations
Cites background from "Dispersion Characteristics of a Rec..."
...Here, this V-shaped metal meander line can be regarded as the planarization of a rectangular helix [23], [24]....
[...]
TL;DR: In this paper, a planar helical antenna is presented for achieving wideband end-fire radiation of circular polarization while maintaining a very low profile, which is formed using printed strips with straight-edge connections implemented by plated via-holes.
Abstract: A planar helical antenna is presented for achieving wideband end-fire radiation of circular polarization while maintaining a very low profile. The helix is formed using printed strips with straight-edge connections implemented by plated via-holes. The currents flowing on the strips and along via-holes of the helix contribute to the horizontal and vertical polarizations, respectively. Besides, the current on the ground plane is utilized to weaken the strong amplitude of the horizontal electric field generated by the one on the strips. Thus, a good circular polarization can be achieved. Furthermore, a tapered helix and conducting side-walls are employed to broaden the axial ratio (AR) bandwidth as well as to improve the end-fire radiation pattern. The designed antenna operates at the center frequency of 10 GHz. Simulated results show that the planar helical antenna achieves wide-impedance bandwidth ( $\vert S_{11} \vert ) from 7.4 to 12.8 GHz (54%) and 3-dB AR bandwidth from 8.2 to 11.6 GHz (34%), while retaining a thickness of only $0.11{{{\lambda }}_0}$ at the center frequency. A prototype of the proposed antenna is fabricated and tested. Measured results are in good agreement with simulated ones.
73 citations
Cites background from "Dispersion Characteristics of a Rec..."
...A rectangular planar helix has found many applications in slow-wave structures [14]–[16] and linearly polarized antennas [17], [18], but little literature has been reported on CP end-fire antennas so far....
[...]
TL;DR: In this article, a planar helix with straight-edge connections and incorporating a coplanar waveguide feed has been designed for operation at W-band and has been fabricated using microfabrication technique.
Abstract: A slow-wave structure (SWS) consisting of a planar helix with straight-edge connections and incorporating a coplanar waveguide feed has been designed for operation at W-band and has been fabricated using microfabrication technique. On-wafer cold measurements have been carried out on a number of fabricated SWSs, and the results are reported here for the first time. The parameters measured are return loss, attenuation, and phase velocity, and the results cover a frequency range of 70-100 GHz. Cold-test parameters of the SWS have been also obtained using simulations, and the effects of fabrication, such as surface roughness, have been accounted for by estimating effective conductivity of different parts of the microfabricated structures. The measured and simulated results match well. The effects of silicon wafer resistivity have been also discussed. Planar helical SWSs fabricated in this manner have application in traveling-wave tubes operating at millimeter wave and higher frequencies.
57 citations
Cites background from "Dispersion Characteristics of a Rec..."
...from a pair of parallel unidirectionally conducting screens [20], [21] or from the rectangular helix [22]....
[...]
TL;DR: In this article, a low-voltage, high-efficiency, and wide-bandwidth W-band traveling-wave tube using a symmetric double V-shaped microstrip meander-line slow-wave structure combined with a sheet electron beam is described.
Abstract: A design study for a low-voltage, high-efficiency, and wide-bandwidth W-band traveling-wave tube using a symmetric double V-shaped microstrip meander-line slow-wave structure combined with a sheet electron beam is described in this paper. The electromagnetic characteristics including the dispersion characteristics, interaction impedance, and transmission characteristics of this structure are presented, and the beam-wave interaction is calculated using particle-in-cell algorithms. Our study shows that, when the design voltage and current of the sheet electron beam are set to 4570 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering several tens of watts output power, and the peak output power is about 110 W with a corresponding gain of 31.4 dB and an averaged electronic efficiency of 12% at 94 GHz.
52 citations
Cites methods from "Dispersion Characteristics of a Rec..."
...This V-shaped microstrip meander-line SWS [17], [18] evolved from the original U-shaped microstrip meander-line SWS [19], [20], combining the advantages of traditional microstrip and the rectangular helix [21]–[23]....
[...]
TL;DR: In this paper, a planar slow-wave structure consisting of a straight-edge connection was studied in the context of application in traveling-wave tubes, and the effects of several practical modifications to the basic structure were examined.
Abstract: A planar slow-wave structure consisting of a planar helix with straight-edge connections has been studied in the context of application in traveling-wave tubes. The effects of several practical modifications to the basic structure are examined. These modifications comprise a vacuum tunnel, metal shield, and multilayer dielectric substrates. A modified effective dielectric constant method is proposed to obtain the dispersion characteristics for different possible configurations. Furthermore, coupling impedance for the different configurations has been calculated using the corresponding 2-D approximations. It is shown that, far from cutoff, the phase velocity and coupling impedance values calculated in this manner match very well with the simulation results obtained from CST Microwave Studio. The effects of variations in aspect ratio, metal shield distance, and dielectric constant of the substrates on phase velocity and coupling impedance are studied. A coplanar waveguide feed has been designed for one of the possible configurations. The measured S-parameters and phase velocity values for this proof-of-concept configuration agree well with the simulated results and confirm the ease of fabrication, low loss, and the wideband potential of the planar helix with straight-edge connections.
44 citations
Cites background or methods from "Dispersion Characteristics of a Rec..."
...Such a rectangular helix has been recently investigated [6]; the dispersion characteristics have been obtained using the approximations of (i) sheath-helix, (ii) average boundary conditions on the four sides of the rectangular helix, and (iii) neglecting the fields in the corner regions outside the helix....
[...]
...It should be noted that even the approximate approach in [6] becomes tedious when applied to multilayer structures that are likely to arise in practice [7]....
[...]
References
More filters
[...]
TL;DR: In this paper, the power output of a traveling-wave tube has been analyzed using a linearized theory only, and no attempt has been made to develop a non-linear theory.
Abstract: A Theoretical Evaluation of the power output of a traveling-wave tube requires a theory of the non-linear behavior of the tube. In this book we have dealt with a linearized theory only. No attempt will be made to develop a non-linear theory. Some results of non-linear theory will be quoted, and some conclusions drawn from experimental work will be presented.
552 citations
[...]
TL;DR: In this article, an electron beam traveling with about 1/13 the speed of light is shot through a helical transmission line with about the same velocity of propagation, and the gain was achieved over a bandwidth 800 megacycles between 3-decibel points.
Abstract: Very-broad-band amplification can be achieved by use of a traveling-wave type of circuit rather than the resonant circuit commonly employed in amplifiers. An amplifier has been built in which an electron beam traveling with about 1/13 the speed of light is shot through a helical transmission line with about the same velocity of propagation. Amplification was obtained over a bandwidth 800 megacycles between 3-decibel points. The gain was 23 decibels at a center-band frequency of 3600 megacycles.
317 citations
"Dispersion Characteristics of a Rec..." refers methods in this paper
...By using the sheath model [9], the boundary conditions at the interfaces are represented as follows....
[...]
...In Section II, the field expressions, dispersion equation, and the coupling impedance are derived using the Sheath model [9]....
[...]
TL;DR: In this paper, a planar structure comprising a pair of parallel arrays of periodically spaced conducting strips which conduct in different directions in the two arrays is considered, and the guiding properties of this plan-ar structure are found to be similar, in one case, to those of circular tape helices.
Abstract: Considered here is a planar structure comprising a pair of parallel arrays of periodically spaced conducting strips which conduct in different directions in the two arrays. The guiding properties of this planar structure are found to be similar, in one case, to those of circular tape helices. While in general, different dielectric media are assumed in the sandwiched and outer regions, the special cases studied are 1) the case in which air constitutes both the media, 2) the normal-helix case in which the inner medium is a solid dielectric and the outer medium is air, and 3) the "inverted-helix" case with the two media interchanged.
32 citations
24 citations