The modal-vertical-beam(MVB) transmission loss analysis

摘要

The group-averaged modal characters (attenuation coefficient, back-scattering coefficient, ...) are important for higher frequency normal mode field modeling. In this paper, the method of extracting the group-averaged modal attenuation coefficient from the Modal-Vertical-Beam (MVB) analysis is discussed. The beamformer output spectrum is consisted of two parts: one is the modal energy weighted sum and another is the intermode interference sum. If the intermode term can be ignored, group-averaged-modal attenuation coefficient can be obtained from the beamformer output at two different ranges. Numerical simulations have been conducted to investigate the effective approaches for reducing the intermode term. Transmission loss data collected by a 57m VLA during the 2001 ASIAEX is also performed.