5G C-band Energy industries & utilities History of engineering & technology RCS reduction RF switching Technology: general issues X-band active FSS antenna array antenna boosters aperiodic array band rejected combo-reconfigurable digitally tunable capacitors dual polarization envelope correlation co-efficient flexible antennas four element MIMO frequency and radiation pattern frequency reconfigurable frequency-selective surface (FSS) full wave analysis leaky waves low-profile magnetic particles magnetostatic responsive structures (MRSs) matching networks metasurface ground plane metasurfaces