I. Introduction
Since the invention of the radar, it has experienced the Second World War and played an important role in it. Now it has become the most effective remote detection equipment. Correspondingly, radar stealth technology has become one of the decisive factors in the battlefield. Radar cross section (RCS) is a very important concept in radar stealth, which characterizes the intensity of the reflected wave produced by an object under the irradiation of electromagnetic waves. Because the radar and antenna have a large RCS, the radar radome needs to have the function of reducing the RCS of the radar and antenna.