A simple transmission line model for narrow slot apertures having depth and losses

A simple transmission line model is given to approximately represent a narrow slot aperture having depth when the conductivity of the conducting plane (and slot walls) is large but not necessarily infinite and when somewhat lossy gaskets are placed in the slot. Slot and gasket dimensions, in addition to the electrical parameters of the conducting plane and gasket, are restricted so that gasket- and wall-loss-effects only need to be included locally (near the slot cross section) and additionally so that the slot voltage is nearly constant locally (however diffusion into the depth of the slot is considered when very lossy gaskets are introduced). Normal incidence is emphasized since this is typically the most important case for slots that are not too long compared to the wavelength. The transmission line model is used to obtain simple approximate formulas for resonant quality factor, slot voltage, penetrant fields, and transmitted power. Low frequency quantities including magnetic dipole moments are also obtained. Gaskets with air gaps are considered and optimum choices for electrical parameters are discussed