Experimental Verification of the Fundamental Gaussian Beam Properties of Smooth-Walled Feedhorns

We report the measurements of near-field patterns for three smooth-walled feedhorns and a conventional corrugated feedhorn at different wavelengths. The measured vector beam patterns are fitted into fundamental Gaussian beam modes. We verify our measurement by comparing the corrugated horn result with its well-established theoretical pattern. The positions and diameters of the beam waists of all of the measured horns are derived from the fitted fundamental Gaussian beam and are in good agreement with those obtained from numerical calculations.