Effect of Thin Plasmas on an Aperture Antenna in an Infinite Conducting Plane

It is shown that for the plasmas present around a wide variety of reentry vehicles, it is acceptable to replace the plasma by an impedance sheet. Using this notion, a variational expression for the admittance of an arbitrary aperture (fed by a waveguide) in an infinite conducting plane covered by an impedance sheet is developed, and examined in some detail. We found that a purely real impedance sheet tends to suppress the higher‐order modes, while a purely imaginary sheet can enhance or suppress the higher modes, depending upon their nature.