Figure 2

(a) Measured LWA prototype for K-band applications with a top MSG defined by 14 annular slots (w = 1.4 mm, p = 5 mm, ρ₀ = 9.3 mm). The LWA is fed by a nondirective SWL placed at the origin, with a 50-Ω coplanar waveguide transmission-line feed system. The LWA (illustrated in Fig. 1) was realized using a high/low dielectric profile of commercially available substrates: ε_r1[2] = 10.2[3], h_1[2] = 1.27 mm (or 50 mil) [1.52 mm (or 60 mil)]. (b) The complex radial wavenumber, k_ρ, of the 2-D LWA can be approximated by the LW propagation constant of an infinite structure with phase advancing normal to the MSG: (b) The infinite ‘bull-eye’ structure with radial propagation; (c) linear infinite analogue. (d) Transverse equivalent network for the evaluation of the spectral Green’s function of the background 2L-GDS. On the top a shunt admittance represents the open space, whereas on the bottom the horizontal line represents a short circuit on the ground plane at z = −(h₁ + h₂).