| 摘要 |
An antenna unit (30) for measuring the velocity of a flowing material by the Doppler effect is particularly suited for use where only a limited space is available. The antenna unit (30) comprises a support block (32) having first and second surfaces (44, 46) disposed at an acute angle (optimally 45 DEG ) relative to each other. A printed circuit antenna card (38) having thereon a high gain antenna comprising a phased array of antenna elements (60) is mounted to the second surface (46) and radiates microwave energy toward the first surface (44). A plate (34) having an opening therein is disposed adjacent the first surface (44), the plate being made of a material which absorbs radiated energy incident thereon. The support block (32) is provided with a recess for receiving an absorber wedge (42) which absorbs the energy radiated in near side lobes. The absorber wedge (42) and plate (34) shape the radiation pattern (86, 88, 90) so that energy radiated by the antenna intercepts the material at an angle of 45 DEG +/-15 DEG when the first surface (44) is disposed parallel to the axis (A-A) of flow. <IMAGE> |
