Optical-controlled Fast Switching of Radio Frequency Orbital Angular Momentum Beams With Different Mode and Radiation Direction

Abstract

The wireless imaging radar need more orbital angular momentum (OAM) modes to irradiate targets alternately to obtain higher azimuth resolution. For that, this present paper investigates the fast-switching technique of radio frequency orbital angular momentum (RF-OAM) beam with the use of an optical-controlled system. Compared with the method using pure electrical device, the optical-controlled method offers conveniences in processing same-frequency radio signal, which will contribute to make the system compact. Moreover, the fast-responding speed of the optical device provide a fast speed of switching. The fast-switching system of RF-OAM beams with different mode and radiation direction is proposed and constructed, and proof-of-concept experiments are performed. The proposed system is realized by employing a program-controlled optical switch and the wavelength multiplexing technique integrated into an optical-controlled circular antenna array (CAA). In the demonstration experiments, the switching between +1-mode and −1-mode RF-OAM beams without steering control is detected within 20 ms, then the system achieves the switching between a +1-mode OAM beam with radiation direction −3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> and a −1-mode OAM beam with radiation direction 3 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> at the same rate.