Low-frequency location of the leaky-wave poles for a dielectric layer

Explicit formulas are presented for the value of the complex longitudinal propagation constant beta -j alpha for the higher leaky modes of a dielectric layer in the low-frequency limit. The formulas give values for beta and alpha for both TE and TM modes and for the cases with and without a metal ground-plane backing. In addition to mathematical derivations, numerical comparisons that demonstrate the accuracy of the formulas derived are presented. The expressions derived for the phase and attenuation constants of the leaky waves become increasingly accurate as the frequency is lowered.<
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