Two types of exciting modes in a rectangular-to-radial waveguide transformer as a feeder of radial line slot antennas

The authors discuss two types of exciting modes in a rectangular-to-radial waveguide transformer for radial line slot antennas (RLSAs). One is the rotating-mode gene a crossed slot in a radial waveguide. The measured ripple of the amplitude is 3.0 dB in the /spl phi/-direction at 5.95 GHz and the bandwidth below 6 dB is 7.0% in the 5.8 GHz band. The other is the coaxial mode; which is proposed in this paper. The calculated ripple of the amplitude in the /spl phi/-direction is about 1.2 dB in the 12 GHz band.