This paper explains a computer technique for accurate and efficient analysis of multi-layer planar antennas fed by planar transmission lines. The technique is based on the electric field integral equation (EFIE) and exploits the Galerkin method in the spectral domain for the moment solution of the equation. Entire domain travelling wave basis functions are used to represent the incident and reflected currents on the feed line. The type of the current expansion on the feed line allows the effects of possible radiation along the feed to be duly accounted for in the computation of the input impedance, radiation patterns etc. The expansion presented can be modified for an approximate analysis. Various structures have been treated by the technique. Results for two examples, a stacked patch antenna fed by a microstrip line and a terminated coplanar strips line are reported and discussed.