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Off-axis feed or offset-feed The primary reflector is asymmetric, with the focus, and the feed, located to one side, outside the beam area. This avoids the problem of the feed obstructing the beam. This avoids the problem of the feed obstructing the beam.
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Main types of parabolic antennas. An offset dish antenna or off-axis dish antenna is a type of parabolic antenna.It is so called because the antenna feed is offset to the side of the reflector, in contrast to the common "front-feed" parabolic antenna where the feed antenna is suspended in front of the dish, on its axis.
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An oblique projection of a focus-balanced parabolic reflector. It is sometimes useful if the centre of mass of a reflector dish coincides with its focus.This allows it to be easily turned so it can be aimed at a moving source of light, such as the Sun in the sky, while its focus, where the target is located, is stationary.
In the presence of astigmatism, an off-axis point on the object is not sharply imaged by the optical system. Instead, sharp lines are formed at the tangential and sagittal foci. The image at the tangent focus is a short line, oriented in the direction of the sagittal plane; images of circles centered on the optic axis, or small lines tangential ...
Several different off-axis configurations are used for radio antennas. [10] Another off-axis, unobstructed design and variant of the Cassegrain is the 'Yolo' reflector invented by Arthur Leonard. This design uses a spherical or parabolic primary and a mechanically warped spherical secondary to correct for off-axis induced astigmatism.