Technologies for Near-Field Focused Microwave Antennas

Figure 5

Ray-optics representation of the field radiated by (a) a rectilinear uniform LW antenna focused in the far-field region; (b) a curved (equiangular spiral shaped) uniform LW antenna focused in the near-field region; (c) a rectilinear tapered forward LW antenna focused in the near-field region; (d) a rectilinear tapered backward LW antenna focused in the near-field region. In (a) and (b), the radiation angle is constant, while in (c) and (d) it varies along the guiding structure.

(a)

(b)

(c)

(d)