A microwave radio frequency bidirectional energy flow-capable antenna method and related antenna of the physically conformal microstrip transmission line, traveling wave and leaky wave characterizations; the antenna is especially suited to vehicle mounting. The disclosed antenna operates in an EH.sub.1 or other above dominant mode energy wave propagation configuration, a configuration at least partially achieved by an array of selected-location radiating element shortings to an antenna-underlying transmission line ground plane element. Comparisons of the disclosed antenna with characteristics of a similarly classified antenna of somewhat lesser desirable but know characteristics are included.
A polarization switching/variable directivity antenna according to the present invention includes a ground conductor plate 12 on a surface of a dielectric substrate 11, and has a radiation element 13, a directivity switching element 15, and polarization switching elements 16 provided on the ground conductor plate 12 side of the dielectric substrate 11. The radiation element 13 includes a first slot 17a formed by removing a loop-like portion from the ground conductor plate 12. The directivity switching element 15 includes a second slot 17b formed by removing a loop-like portion from the ground conductor plate 12 and directivity switching switches 18. The polarization switching elements 16 includes a third slot 17c formed by removing a linear-shaped portion from the ground conductor plate 12 and polarization switching switches 19a to 19d. Through control of the directivity switching switches 18, switching of a maximum gain direction of radiation directivity of the antenna is realized. Through control of the polarization switching switches 19a to 19d, switching of a rotation direction of a circularly polarized wave which is emitted from the antenna can be realized.
