A Slot Antenna Array With Reconfigurable RCS Using Liquid Absorber

A method is presented to achieve a slot antenna array with a reconfigurable radar cross section (RCS) by injecting and extracting ethanol. In a complex communication system, this can be used to switch between the detection and stealth modes. The antenna system is formed by combining a liquid absorber with a $2\times $ 2 slot antenna array. The liquid absorber consists of a polymethyl methacrylate (PMMA) container, 45% ethanol layer, and metal ground, which is attached to the surface of the slot antenna array. The incident wave can be absorbed by the absorber rather than reflected in other directions when the PMMA container is filled with ethanol, which reduces the monostatic and bistatic RCS. Thus, the RCS of the antenna can be changed by injecting and extracting ethanol while sustaining the antenna’s radiation performance in terms of bandwidth, radiation patterns, and gain. The mechanism of the absorber is investigated. The simulated results show that the antenna with this absorber has monostatic and bistatic RCS reduction bands from 2.0 to 18.0 GHz and a maximum RCS reduction of 35 dB with an average RCS reduction of 13.28 dB. Without ethanol, the antenna realizes a gain of 12.1 dBi, which drops by 2 dB when the lossy ethanol is injected. The measured and simulated results agree well.