Multifunctional Time-Modulated Metasurface-Enabled Electromagnetic Tags for Cooperative Target Recognition

In this article, we propose a multifunctional time-modulated metasurface-enabled electromagnetic (EM) tag as a low-complexity, low-cost, and effective alternative for cooperative target recognition. The novel metasurface can execute reflection, absorption, and detection functions within a singular structure, capable of switching among the three impedance states of p-i-n diode. Following the cooperative target identification mechanism, the metasurface tag applies time-modulated sequences to the cooperative radar signals. The realized different discrete frequency components give distinguishable coding signatures to it. While for non-cooperative radar signals, the tag operates in an absorbing state to achieve EM stealth. A prototype working within Ka-band is fabricated and tested, revealing features like a wideband, dual-polarization amplitude modulation, and detection functionality. These outcomes align with simulation expectations and validate the functionalities of the metasurface tag. Further, the anechoic and real scenario experiments demonstrate that the metasurface tag offers the ability to assist in target recognition with reading stability and coding extensions.