The fields associated with an interface between free space and an artificial dielectric

In most respects artificial dielectrics behave in a similar way to normal solid dielectrics. A complication is sometimes observed in that apparent phase discontinuities occur at the interface between free space and an artificial dielectric, such discontinuities arising from the excitation of reactive fields near the interface. It is shown that the behaviour can be analysed in terms of evanescent waves inside the dielectric and in free space, and detailed calculations are given for the metal-strip type of delay dielectric. Measured values of the parameters of an equivalent circuit representing the free-space/artificialdielectric interface are shown to agree with calculated values within the limits of experimental error.