Reradiation (echo) analysis of a tapered tower section supporting aside-mounted DTV broadcast antenna and the corresponding azimuth pattern

摘要

Reradiation from a non-vertical obstruction such as a tapered section of a broadcast antenna supporting tower is analyzed. The reradiation takes on the form of a cone, which is symmetrical about the tower leg axis, modified by the reflection coefficient that varies with azimuth. The reradiation is directed either above the horizon where it is lost or below the horizon where it interferes as an echo with the direct radiation. The reradiation has an elevation pattern which is a replica of the transmitting antenna elevation pattern, but is redirected by the nonvertical tower leg. The reradiation combines with the direct radiation to form an azimuth pattern which varies with distance from the broadcast antenna. The reradiation, being an echo, is analyzed for multipath distortion of the VSB pulse. It is shown that the impact on DTV receiver threshold is minimal