The leaky-wave antenna (LWA) is a traveling wave antenna that uses a fast wave
as the main radiating mechanism, where the fast wave is radiating continuously along
the structure. Depending on the length of the antenna, some part of the fast wave
gets reflected from the end and causes another beam in the opposite direction. The
effects of the reflected fast wave on the radiation pattern can be analyzed if the
reflection coefficient at the end of the antenna is known, which can be obtained from
the complex amplitude and propagation constants associated with the fast waves.
Even the radiation pattern of a LWA can be obtained using the reflection coefficient
and propagation constants.
Closed top guiding structures, a dielectric slab waveguide, 2-D LWAs and 3-D
LWAs are modeled in a commercial full wave MoM solver, FEKO. The near-field
samples are calculated along the structure. For these types of structures, the total
near field can be expressed as a sum of complex exponentials. The matrix pencil
method (MPM) is a most accurate and efficient linear technique to approximate a
function by a sum of complex exponentials. The exponential components from the
total near field use the complex propagation constants inside the structure, which are
calculated using the MPM. The MPM extracted amplitude and phase components
are used to calculate the reflection coefficients of the structures and radiation patterns
of the LWAs.
The accuracy of this approach is verified using various open and closed guiding
structures in 2-D and 3-D, and by comparing the results with available numerical and
experimental results.