The characteristic impedance and phase velocity of high-Q triplate line

The derivation of the impedance and phase velocity for high-Q triplate line is considered. An exact solution is obtained for the impedance in the absence of the dielectric support sheet. The effect of the sheet is then considered as a perturbation, the analysis resulting in an expression for the phase velocity of the waves in the line. This is compared with experimental values and it is shown that the agreement is sufficiently close for design purposes.