A NOVEL NONCONTACTING WAVE-GUIDE BACKSHORT FOR SUBMILLIMETER-WAVE FREQUENCIES

A novel noncontacting waveguide backshort has been developed for milli meter wave and submillimeter wave frequencies. It employs a metallic b ar with rectangular or circular holes. The size and spacing of the hol es are adjusted to provide a periodic variation of the guide impedance on the correct length scale to give a large reflection of rf power. T his design is mechanically rugged and can be readily fabricated for hi gh submillimeter wave frequencies where conventional backshorts are di fficult or impossible to fabricate. Model experiments have been perfor med at 4 GHz - 6 GHz to empirically optimize the design parameters. Va lues of reflected power greater than 95% over a 30% bandwidth have bee n achieved. A specific design is presented which has also been success fully scaled to WR-10 band (75 GHz - 110 GHz). A theoretical analysis is compared to the experiments and found to agree well with the measur ed data.