Traveling-wave loop antenna based on metal ring cavity for generating radio frequency orbital angular momentum

摘要

A traveling-wave loop antenna based on a metal ring cavity for generating a radio frequency OAM beam includes a main structure which is the metal ring cavity whose top surface has an annular slot circumferentially opened. Two openings ¼ of a perimeter of the metal ring cavity apart, are two excitation source ports of the antenna, for connecting a metal waveguide. When the two ports are inputted with microwave sources having the same frequency and a phase difference of ±90°, an electromagnetic field in the metal ring cavity exhibits a traveling-wave distribution propagating circumferentially clockwise or counterclockwise. The annular slot constitutes the antenna. A reasonable design of a size of the metal ring cavity and a position of the annular slot realizes a conversion from a microwave guided-wave mode to an OAM mode and a generation of the radio frequency OAM beams with different orders l in free space.