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^o and a −1-mode OAM beam with radiation direction 3^o at the same rate.

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