Low reflection coefficient waveguide termination using an imaging method

In this paper resonant elements are arranged in such a way that results in self cancelling images when used as a termination in rectangular, square, or circular waveguide. This results in a low reflection coefficient when measured at the waveguide input. The terminations selected are, for the rectangular and square waveguide, a short circuited circular disk microstrip resonator, and for the circular waveguide, a half-wavelength dipole placed one quarter of a wavelength above a ground plane. In the former cases 18% bandwidth reflections of less than -15 dB were achieved at a 2.8 GHz centre frequency while in the circular waveguide case 20% bandwidth with better than -20 dB was achieved for a 9 GHz centre frequency.