Applying microfabrication to helical vacuum electron devices for THz applications

Dayton, J.A.; Kory, C.L.; Mearini, Gerald T.; Malta, Dean; Lueck, Matthew; Gilchrist, Kristin H.

doi:10.1109/ivelec.2009.5193352

Cited by 18 publications

(11 citation statements)

References 6 publications

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“…For instance, structures called square helix and planar helix, compatible with microfabrication technology, have been proposed and computationally investigated in [12] for Ka-band applications, but no results for fabrication and measurements have been provided. Design and fabrication of 95-GHz TWT and 650-GHz backward-wave oscillator based on microfabricated helix has also been reported extensively [13], [14]. However, these papers do not discuss dispersion control or dispersion shaping.…”

Section: Introductionmentioning

confidence: 99%

Vane-Loaded Planar Helix Slow-Wave Structure for Application in Broadband Traveling-Wave Tubes

Swaminathan

Zhao

Chua³

et al. 2015

IEEE Trans. Electron Devices

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Dispersion control of a planar helix slow-wave structure (SWS) using vane loading for applications in travelingwave tubes has been studied. The addition of metal vanes and coplanar ground planes to the planar helix structure has been investigated with the help of simulations aimed at achieving low or negative dispersion. It is shown that, similar to the case of circular helix, the addition of metallic vanes to the planar helix can produce a flatter dispersion curve or negative dispersion characteristics. Furthermore, it is shown that even stronger dispersion control can be achieved by the use of metal vanes together with extended coplanar ground planes on the dielectric substrates that support the planar helix. As a proof of concept, one of the designs of the planar helix SWS including metal vanes and operating at S-band frequencies has been fabricated and tested; the measured phase velocity results match the simulation results very well.Index Terms-Broadband traveling-wave tubes (TWTs), coplanar ground plane, planar helix, slow-wave structure (SWS), vane loading.

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Section: Introductionmentioning

confidence: 99%

Vane-Loaded Planar Helix Slow-Wave Structure for Application in Broadband Traveling-Wave Tubes

Swaminathan

Zhao

Chua³

et al. 2015

IEEE Trans. Electron Devices

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“…With regard to high frequency VEDs, microfabrication of several SWSs has been reported in the literature. [36], double corrugated waveguide [94], raised meander-line [37], biplanar interdigital [38], and circular helix [38] and [95] Unlike the all metal structures, the structures that involve dielectric loading normally require more fabrication steps since the metallization is on top of a patterned dielectric substrate. For instance, the raised meander-line structure [37] involves selectively metalizing the high-aspect-ratio serpentine dielectric ridge.…”

Section: Microfabrication Of Swssmentioning

confidence: 99%

“…Many efforts have been made to reduce the dielectric surrounding the structure. The fabrication of circular helix [38] and [95] involves a thin sheet of diamond for supporting the structure; such a configuration enjoys excellent thermal dissipation, moderate dielectric loading, high dielectric strength and low loss. However, the circular shape is difficult to realize faithfully in microfabrication and may need to be approximated as octagonal or square [95].…”

Section: Microfabrication Of Swssmentioning

confidence: 99%

“…The fabrication of circular helix [38] and [95] involves a thin sheet of diamond for supporting the structure; such a configuration enjoys excellent thermal dissipation, moderate dielectric loading, high dielectric strength and low loss. However, the circular shape is difficult to realize faithfully in microfabrication and may need to be approximated as octagonal or square [95]. Among the various SWSs, in general the helix structure holds a unique position since the fabrication has less stringent alignment issues due to their broadband nature [38].…”

Section: Microfabrication Of Swssmentioning

confidence: 99%

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Studies on planar helical slow-wave structures for traveling-wave tube applications

Chua¹

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“…In traditional circular helix TWTs, thin rectangular support rods made of Beryllium oxide (BeO, ɛr = 6.5) or APBN (ɛr = 5.1) are most widely used, as shown in Figure 1.2 [4]. For some recent microfabricated SWSs, silicon (ɛr = 11.9) [24], [59] or diamond (ɛr = 5.7) [63]- [65] have been used as supporting dielectric materials.…”

Section: Dielectric Loadingmentioning

confidence: 99%

Planar helix-based slow-wave structures for millimeter wave traveling-wave tubes

Zhao¹

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Circular helix is a very popular slow-wave structure (SWS) for application in traveling-wave tubes (TWTs). But it is not easy to be fabricated using printed-circuit or microfabrication techniques which are important for low-cost fabrication and high frequency applications. In this context, during the last few years, a planar helix SWS with straight-edge connections (PH-SEC) has been proposed and studied. Unlike the circular helix, the PH-SEC is suitable to be fabricated using printed circuit or microfabrication techniques. However, there are still some issues and problems that need to be addressed for the PH-SEC when used in millimeter wave TWTs. First of all, there can be backward wave oscillations when the TWT is working at high voltages. Secondly, the size of the SWS, the electron beam tunnel, and the beam get very small, causing difficulty in fabrication, alignment, and focusing of the electron beam. Thirdly, at millimeter wave frequencies, it is more likely that the electrons hit the supporting dielectric, causing dielectric charging which will affect the performance of the TWT adversely. Moreover, PH-SEC can be dispersive in the presence of dielectric loading, reducing the bandwidth of operation. This thesis presents novel SWSs which are based on the PH-SEC and solve some of these problems. First of all, two types of coupled planar helices, an unconnected pair of PH-SECs and a coaxial pair of PH-SECs, are proposed. Their dispersion characteristics are derived from analysis based on field-theory. The characteristic equations and field expressions are obtained to explain the nature of different modes that propagate in the coupled structures. Coupling impedance is also calculated. Effects of variations in dimensions are studied. The analysis results match well with simulations. Simulation results are presented to show that the unconnected pair of planar helices has a reduced interaction with backward waves as compared to that for a corresponding single PH-SEC. Based on the above knowledge of various modes, an unconnected pair of PH-SECs has been designed together with a stripline power divider in order to provide input signals with equal magnitude and phase. Also proposed is a connected pair of PHvi SECs which can be fed in a much simpler way by a coplanar waveguide (CPW) feed. The latter structure offers a larger electron-beam tunnel and lower risk of backward wave oscillation compared to the single PH-SEC. Moreover, the connected pair of PH-SECs has a higher gain growth rate than that for the single PH-SEC. The connected pair also shows a significantly higher coupling impedance compared to a recently reported meander-line based SWS. Both the unconnected and the connected pair of PH-SECs have been designed and fabricated using printed circuit techniques. The measurement results match well with the simulation results.

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Applying microfabrication to helical vacuum electron devices for THz applications

Cited by 18 publications

References 6 publications

Vane-Loaded Planar Helix Slow-Wave Structure for Application in Broadband Traveling-Wave Tubes

Vane-Loaded Planar Helix Slow-Wave Structure for Application in Broadband Traveling-Wave Tubes

Studies on planar helical slow-wave structures for traveling-wave tube applications

Planar helix-based slow-wave structures for millimeter wave traveling-wave tubes

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