Perturbation Analysis of a Planar Periodic Leaky-Wave Antenna Fed by Surface Waves

We consider a printed leaky-wave antenna composed of a grounded substrate topped by a periodic metallic screen or grating. The antenna is fed by the TM
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surface-wave mode that is launched by an array of slots in the ground plane. The leaky-wave attenuation and phase constants are derived using a simple but accurate field perturbation approach. The radiation power, directivity, and beam patterns are also deduced. Numerical results show that, depending on the screen period and the substrate height, there is an optimum frequency range for maximum radiative power. In addition, calculated results are also in agreement with simulations and measurements for some recently designed and fabricated structures.