Linear array of longitudinal slots excited by metal supports on a hollow rectangular coaxial line

Due to the possibilities of high gain, high efficiency and height reduction, slotted waveguide array antennas have been widely used in many millimeter-wave applications such as radar systems and fixed wireless access systems. The fabrication technique by diffusion bonding of laminated thin plates ensures low cost and high precision of the slotted waveguide array antennas [1]. However, the slotted waveguide array antennas have limitation for wide beam scanning without grating lobes because the width of a rectangular waveguide is more than 0.5 λ₀, typically 0.7-0.8 λ₀, to support the dominant TE₁₀ mode. A rectangular coaxial line is one candidate for the width reduction of a transmission line. A linear array of inclined slots on a hollow rectangular coaxial line with the width of 0.4 λ₀ was proposed by Yamaguchi et al. [2]. The linear array is realized by laminating several aluminium plates and screwing them. Since the inner conductor is supported only at the both ends, stable operation is limited to a small array. For a larger array, we have considered the connection between inner and outer conductors with metal supports, and excitation of a longitudinal slot by the support [3]. The diffusion bonding is adopted to form the support and to realize perfect electrical contact between the plates. This paper presents a linear array of the longitudinal slots on a hollow rectangular coaxial line in the 60 GHz band.