Inclined slot array antennas on a rectangular coaxial line

Slotted-waveguide array antennas are attractive because of their low-loss characteristics in high frequencies. Several types of slotted arrays whose polarization angles are inclined to the waveguide axis have been reported. In this paper, we propose a new type of slot array antennas on a rectangular coaxial line for minimizing the waveguide width. As opposed to a conventional waveguide, there is no “cut-off” concept in the present case because the coaxial line is a TEM-line. Therefore it is possible to guide the wave even if the diameter of the line is much smaller than that of the waveguide. Moreover, this antenna is a resonant slot array antenna that is based on standing-wave excitation and is thus different from a travelling-wave antenna (such as a leaky coaxial cable (LCX)).