  Orbital angular momentum (OAM) has gradually become a research hotspot in
radar, communication and other fields because of its phase distribution.
However it encounters some problems in the real practice owing to its inherent
characteristics. Recently OAM mode group has been proposed to solve these
problems. In this paper, a non-uniform OAM source is used to generate the OAM
mode-group (MG) directly. The radiation field is analyzed based on an
equivalent source transformation. Taking the partial arc transmitting (PAT)
scheme as an example, the non-uniform source is equivalenced as a group of
uniform OAM sources by calculated its Fourier transform. This work provides
theoretical guidance for the design of non-uniform OAM antenna in the RF
domain.
