the graph 60 in which a pronounced minimum 64 occurs at 14 9 ghz this is the resonant frequency of the resonator 28a with an air dielectric over the superstrate 32 of fig2 when a one millimeter layer 68 of ice the layer 68 is indicated by a broken line in fig2 is added to the superstrate 32 the pattern of the electromagnetic field lines between the signal line 29a and the ground plane 26 is altered because the permittivity of ice differs from that of air the resonator 28a initially operates with an effective permittivity u03b5 eff which is associated with the permittivity of air and the substrate 30 because the electromagnetic field lines of the resonator flow across both of these media as the ice layer 68 develops on the superstrate 32 its permittivity also contributes to the effective permittivity u03b5 eff accordingly the resonant frequency of the resonator 28a is shifted downward as a consequence the graph 60 shows a minimum 70 in the reflection coefficient at 12 6 ghz the minimum 70 has a lower reflection coefficient than that of the minimum 64 which indicates that the alteration of the effective permittivity u03b5 eff has also increased the q quality factor of the resonator 28a as the thickness of the ice layer 68 is increased the pattern of the electromagnetic field lines between the signal line 29a.