COMPACT HE-11 TO SURFACE-WAVE CONVERTERS FOR HIGH-POWER WAVE-GUIDE DUMMY LOADS

The HE11 mode in corrugated circular waveguide can be converted to the EH11 mode (surface wave) by a short, smooth-waveguide phase shift section followed by a short corrugation depth taper. Low-power measurements at 110 GHz in 1.25 in. aluminum waveguide demonstrated approximately 99% conversion with the proper phase shift length. As expected, the conversion efficiency versus length of the phase shifter varied periodically with the period of the TE11 to TM11 beat wavelength. Since the EH11 surface wave is highly attenuated, this type of converter can be used effectively in a compact high-power dummy load.