Guided Waves on a Planar Helix

Planar helix slow-wave structure with straight-edge connections in the presence of coplanar ground planes

“…The PH-SEC can be considered to be derived from a pair of parallel unidirectionally conducting (UC) screens [3], also called planar helix [4], by adding transverse confinement. Alternatively, the PH-SEC can also be considered to be a modification of the rectangular helix, replacing inclined-edge connections between the top and bottom helical metal strips by straight-edge connections.…”

Polarization of wall currents for a planar helix enclosed in a rectangular waveguide

“…A novel structure consisting of a pair of uni-directional conducting (UC) screens sandwiching a dielectric substrate and enclosed in a rectangular waveguide is shown in Fig 1a and Fig 1b.The dielectric regions on either side of the UC screens are different in general, as shown in Fig 2a. The UC screens consist of discrete, narrow and closely spaced conducting strips placed at regular intervals with symmetric inclination α and − α with respect to the y axis as shown in Fig 2b. A pair of UC screens, whether infinite [1] or confined in the y-direction [2], has been seen to emulate the slow wave properties of the circular helix and hence has been referred to as the 'planar helix' [1,2]. The present structure is confined in both x and y directions and has shown considerable size reduction over a corresponding dielectric-loaded waveguide [3].…”

“…This is illustrated in Fig 4. In fact J y is nearly zero throughout the region -a/2 < y < a/2. This may be explained by the fact that H z1 (Appendix) is very small; because the value of k 0 chosen is very close to β, the (k 1 2 -β 2 ) term tends to zero. The sidewalls have two distinct regions adjoining the dielectric (-b/2<x<b/2) and above and below the dielectrics.…”

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

“…The PH-SEC can be considered to be derived from a pair of parallel UC screens [18]- [19], or from the rectangular helix [26]. The PH-SEC retains the broad bandwidth feature of the conventional circular helix.…”

“…19 shows the scanning electron microscope (SEM) micrograph of the microfabricated PH-SEC. The main challenges in this fabrication process include (i) producing high aspect ratio vertical pillars, or vias, using a thick positive photoresist, and (ii) building suspended helix bridges on top of the thick photoresist sacrificial layer.…”