电小尺寸粒子的散射可由瑞利公式描述，其散射源于感应电流的二次辐射，因此无论多小的瑞利粒子均有散射场，其理论上是可探测的。近年来，在光学纳米结构中发现了一类具有散射截面零点的“Scattering dark state (SDS)”粒子。由于该种粒子利用了金属在光频段的等离子色散效应，因而不能通过尺度变换在微波频段得到。本项目研究有源SDS粒子在微波频段的理论、实现方法和应用实例，将解决目前SDS粒子需要等离子体谐振以及无源粒子工作带宽过窄问题。在此基础上，人工实现在周期、非周期分布下均可实现透明的有源SDS粒子。基于有源SDS粒子的可调性，我们设计一种可在多频带进行透明与非透明状态之间切换的衍射媒质，并研究其在多频共享口径波束扫描天线中的应用。本项研究于对隐身天线罩、波束扫描天线等领域有着重要科学意义。

The scattering of electrically small particles which comes from secondary radiation of induced current can be described by Rayleigh formula. Therefore, for arbitrary small Rayleigh particles, they are theoretically detectable due to the non-zero scattering. Recently, scientists found that zero scattering cross section can be obtained in a kind of optical nano-structured particles, referred as “Scattering dark state” particles. The proposed particles utilized the plasmonic dispersion effect of metal in optical band which making them cannot be obtained by size transform in microwave band. This project investigates the theory, realization and applications of active SDS particles, which will eliminate the requirement of plasmonic resonances and the limit of narrow band of passive SDS particles. Then, the active SDS particles which can be transparent in both periodic and non-periodic distributions are artificially realized. Base on the tunability of active SDS particles, we design a diffractive medium that can switch between transparent and opaque state at multiple bands. Further, the applications of diffractive medium for multiple-frequencies share-aperture beam steering antennas are investigated. The researches in this project have important significance in the field of invisible antenna radome and beam steering antenna.