In this letter, to verify that the shaped beam feed can enhance the aperture usage efficiency of a single‐offset parabolic reflector compact antenna test range (CATR), a shaped beam horn is proposed. First, we obtain the radiation intensity function of the feed. Then, a coaxial cavity horn feed with a half‐ring is designed to shape the illumination that reaches the main reflector. Measured results demonstrate that, with no edge treatment, the quiet zone size can be up to 75% of the main reflector diameter under 1.20 dB amplitude variations and 12° phase variations at 102.40 GHz, and 70% aperture usage efficiency ranging from 102 to 103 GHz with phase variations less than 12° and amplitude variations less than 1.40 dB. The design verifies that the shaped beam feed can enhance the aperture usage efficiency of a single‐offset CATR.