Analytical Dispersion Characteristic of a Gap-Groove Waveguide

Abstract

Abstract-A new type of waveguide based on the gap waveguide concept is here proposed and called gap-groove waveguide. Its design is based on the realization of a groove on a metal, facing an artificial surface which creates a high impedance surface (HIS) boundary condition. This condition is achieved here by employing a structure of closely packed metallic pins, known as bed of nails. The type of modes that can propagate in the gap-groove waveguide are similar to the ones of a standard waveguide but in this case there is no need of electrical connection. This is a potential advantage, especially when working at high frequencies. The dispersion characteristic of the gap-groove waveguide is derived by solving an eigenvalue problem, settled through a resonance condition at the interface between the groove and the bed of nails. The eigenvalues are associated with the modes propagating in the waveguide, and their dispersion characteristic is analyzed and compared with full wave simulations. A procedure to maximize the bandwidth is also provided, based on an appropriate choice of the geometrical parameters. Furthermore, the field distribution and the modal impedance of the fundamental mode are investigated.

A Novel Gap-Groove Folded-Waveguide Slow-Wave Structure for G-Band Traveling-Wave Tube

“…According to these considerations, the electric field transverse profile of the dominant mode of the GGW is expected to be similar to one half of the TE 10 mode in a rectangular waveguide, as shown in Fig. 2 [16]. Meanwhile, the electric field maximum of this fundamental mode is approximately at the groove aperture (z = 0).…”

“…According to Fig. 2, the propagating fields in the GGW are concentrated in a groove aperture, realized in a metallic surface, and covered by a contactless bed of nails with a gap separation [16]. This bed of nails is designed to create a high impedance condition over the GGW for providing a hard surface wall to the groove aperture.…”

A Reciprocity Method of Analysis for Gap Waveguide Slot Antennas

“…By exploiting the approximation used for the surface admittance, the imaginary part of the characteristic impedance is also neglected. For both the TE and TM cases, the real part of the characteristic impedance calculated by (18) are compared with the results of CST and are shown in Fig. 10.…”

“…Also, quasi-transverse electromagnetic modes (Q-TEM) are assumed in the ridge region and TE 10 in the groove region. In this way, the dispersion characteristics can be derived for ridge gap waveguide (RGW) [16], [17], and groove gap waveguide (GGW) [18]. Another way is to derive Green's functions of the ridge gap waveguide structures by using asymptotic boundary conditions (BC) for the lower plate and appropriate BCs for the upper plate.…”

A leaky-wave groove antenna at optical frequency

“…This configuration is constituted by an air-aluminum-silver structure where the slot is realized in the aluminum sheet and the silver acts as a dielectric. Here, after formulating the dispersion relation of the dominant mode by using the effective index method, 19,20,23 we compare this result with a full-wave simulation obtained through the commercial software CST Microwave Studio. 25 Our simple, but effective formulation allows for the identification of the frequency range where the fundamental mode supported by the slot antenna is radiative (leaky), and for the investigation of the radiation properties.…”