A moment method analysis of a microstrip antenna fed by an open-end co
planar waveguide is presented. The surface electric current on the mic
rostrip antenna is represented by the entire domain basis functions, w
hile the surface magnetic currents in the open-end slot and in the slo
ts of the coplanar waveguide near the open end are expanded by the sub
sectional roof-top basis functions. Some practical numerical aspects a
re carefully discussed, and a numerical device is introduced to reduce
the computation time for the integrals involving roof-top basis funct
ions and the spectral-domain Green's function. The solution accuracy i
s thus improved. Computed results for the reflection coefficients and
input impedances are given and compared with measured values. Good agr
eement between theory and experiment is obtained.