# Field Theory of Planar Helix Traveling-Wave Tube

TL;DR: In this paper, a planar helix is proposed as a slow-wave structure for application in a traveling-wave tube (TWT) and field theory is applied to analyze the behavior of the planar structure in the presence of a flat electron beans present between the two screens.

Abstract: A pair of unidirectionally conducting screens, conducting in different directions, constitute a planar helix. The planar helix is proposed as a slow-wave structure for application in a traveling-wave tube (TWT). Field theory is applied to analyze the behavior of the planar helix in the presence of a flat electron beans present between the two screens. Results indicate the presence of three modes, with one mode having a negative attenuation constant, as in the case of the usual helix-type TWT. Curves are shown for a typical proposed planar TWT. Also, the effect of beam current is indicated.

##### Citations

More filters

••

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.

47 citations

### Cites background or methods from "Field Theory of Planar Helix Travel..."

...interaction impedance for different possibilities of fabricating the planar helix on dielectric substrates are obtained in [6]....

[...]

...Moreover, a planar helix TWT based on this structure is proposed, and the model solution is obtained in [6] and [7]....

[...]

••

TL;DR: In this article, a rectangular tape helix slow-wave structure with infinitesimal thickness and finite width in free space is investigated, and the dispersion properties and the interaction impedance for transverse antisymmetric modes are obtained.

Abstract: A rectangular tape helix slow-wave structure with infinitesimal thickness and finite width in free space is investigated. With the expansion of surface currents in the helix and the applications of the modified Marcatili’s method, as well as average power flow matching method at the boundaries, the dispersion properties and the interaction impedance for transverse antisymmetric modes in a rectangular tape helix immersed in free space are obtained. It is shown that, compared with the results of the simplified sheath model by previous researchers, higher accuracy has been obtained between the calculation results of the present theory and the data obtained from HFSS, and the validity of the present theory is further demonstrated by comparison with experiments. The improved characteristic equations hold scientific and practical significance in the design and performance evaluation of such plane slow-wave structure in the application of compact traveling-wave tubes. The distribution characteristics on the cross section of the longitudinal electric field fundamental component are also discussed based on this theory.

18 citations

••

TL;DR: In this article, a new type of printed rectangular helix slow-wave structure (SWS) was investigated using the field-matching method and the electromagnetic integral equations at the boundaries.

Abstract: A new type of printed rectangular helix slow-wave structure (SWS) is investigated using the field-matching method and the electromagnetic integral equations at the boundaries. The radio-frequency characteristics including the dispersion equation and the coupling impedance for transverse antisymmetric (odd) modes of this structure are analysed. The numerical results agree well with the results obtained by the EM simulation software HFSS. It is shown that the dispersion of the rectangular helix circuit is weakened, the phase velocity is reduced after filling the dielectric materials in the rectangular helix SWS. As a planar slow-wave structure, this structure has potential applications in compact TWTs.

15 citations

### Additional excerpts

...[2–7]....

[...]

••

TL;DR: In this article, the authors investigated the properties of traveling wave-beam interaction in a rectangular helix traveling-wave-tube (TWT) for a solid sheet electron beam.

Abstract: This paper investigates the properties of traveling wave-beam interaction in a rectangular helix traveling-wave-tube (TWT) for a solid sheet electron beam. The ‘hot’ dispersion equation is obtained by means of the self-consistent fleld theory. The small signal analysis, which includes the efiects of the beam parameters and slow-wave structure (SWS) parameters, is carried out by theoretical computation. The numerical results show that the bandwidth and the smallsignal gain of the rectangular helix TWT increase as the beam current increases; and the beam voltage not obviously in∞uences the small signal gain. Among difierent rectangular helix structures, the small-signal gain increases as the width of the rectangular helix SWS increases, however, the bandwidth decreases whether structure parameters a and

8 citations

••

TL;DR: In this paper, a 1D nonlinear theory of a rectangular helix traveling-wave tube (TWT) interacting with a ribbon beam was presented, where the RF field was modeled by a transmission line equivalent circuit, the ribbon beam is divided into a sequence of thin rectangular electron discs with the same cross section as the beam, and the charges are assumed to be uniformly distributed over these discs.

Abstract: A 1-D nonlinear theory of a rectangular helix traveling-wave tube (TWT) interacting with a ribbon beam is presented in this paper. The RF field is modeled by a transmission line equivalent circuit, the ribbon beam is divided into a sequence of thin rectangular electron discs with the same cross section as the beam, and the charges are assumed to be uniformly distributed over these discs. Then a method of computing the space-charge field by solving Green's Function in the Cartesian Coordinate-system is fully described. Nonlinear partial differential equations for field amplitudes and Lorentz force equations for particles are solved numerically using the fourth-order Runge-Kutta technique. The tube's gain, output power, and efficiency of the above TWT are computed. The results show that increasing the cross section of the ribbon beam will improve a rectangular helix TWT's efficiency and reduce the saturated length.

6 citations

##### References

More filters

••

01 Jul 1948TL;DR: In this paper, the authors considered the problem of a helix-type traveling-wave amplifier tube, under certain simplifying assumptions, and showed that the presence of the beam in the helix causes the normal mode to break up into three modes with different propagation characteristics.

Abstract: The problem of a helix-type traveling-wave amplifier tube, under certain simplifying assumptions, is solved as a boundary-value problem. The results indicate that the presence of the beam in the helix causes the normal mode to break up into three modes with different propagation characteristics. Over a finite range of electron velocities one of the three waves has a negative attenuation, and is thus amplified as it travels along the helix. If the electron velocity is too high or too low for net energy interaction, all three waves have purely imaginary propagation constants; no amplification occurs. Consideration of the beam admittance functions shows that, during amplification, the electron beam behaves like a generator with negative conductance, supplying power to the fields through a net loss of kinetic energy by the electrons. Curves are shown for a typical tube, and the effects of beam current and beam radius are indicated. The initial conditions are investigated, as are the conditions of signal level and limiting efficiency. In the Appendix a simple procedure for computing the attenuation constant is given.

102 citations

••

01 Feb 1947

TL;DR: In this paper, a tube based on the principle of interaction between a traveling electric field and an electron beam traveling at about the same velocity was described and experiments on the interaction and the construction of a tube run as a sensitive amplifier at a wavelength of 9.1 centimeters are given.

Abstract: A tube is described which is based on the principle of interaction between a traveling electric field and an electron beam traveling at about the same velocity. Experiments on the interaction and the construction of a tube run as a sensitive amplifier at a wavelength of 9.1 centimeters are given. A noise factor of 11 decibels with a power amplification of 14 were obtained with one particular tube. An investigation of the field obtaining in a helix-the structure used for slowing down the wave-is briefly described, and the main results of an approximate theory of the tube are given.

83 citations

••

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

••

01 May 1956TL;DR: In this paper, the problems involved in designing traveling-wave tubes in the range of pulsed powers of the order of a megawatt are discussed, together with their advantages and limitations.

Abstract: This paper discusses the problems involved in designing traveling-wave tubes in the range of pulsed powers of the order of a megawatt Suitable circuits are described, together with their advantages and limitations In general, the all-metal structures described are capable of dissipating high average powers, have good impedances at the required voltages (100-kv range), but at a sacrifice in bandwidth Nevertheless, this class of traveling-wave tube is useful where bandwidths of 10 to 20 per cent, not obtainable from klystrons of equivalent power outputs, are of interest The problems of tube construction and tube design are discussed Results of tests on an experimental model tube are described, showing good agreement with available theory A gain uniformity of 3 db over a 9 per cent bandwidth, with power outputs of 300 kw pulsed have been obtained using attenuators of nonoptimum design Better performance should be obtainable with further improvements in beam focusing and coupler design Higher power levels with same effliciency should be possible, by designing the tube to operate at higher potentials

28 citations