Mode selection characteristics in a circular waveguide loaded with a left-handed metamaterial.

We theoretically study mode selection characteristics in a left-handed metamaterial (LHM) loaded into a circular waveguide. The existent modes in the circular waveguide are closely related to the radius of the coaxially loaded LHM, and a general rule that determines whether one mode can exist in the structure is given in this paper. Therefore, the modes in the circular waveguide can be controlled by adjusting the radius of the loaded LHM. For a specific, normalized boundary radius, only one mode is capable of existing in the structure. Moreover, we discuss the variation in the cutoff frequency for different modes as a function of the LHM radius. We find that the eigenfrequencies of almost all waveguide modes increase sharply when the LHM radius approaches half the waveguide radius. These properties may lead to a wide range of applications such as controllable mode microwave generators and perfect waveguide reflectors. [ABSTRACT FROM AUTHOR]