Use of arrays for increasing antenna gain are an alternative to so-called " aperture antennas ", in which the gain is achieved using a single geometric structure, more akin to an optical focusing device.
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A simple acquisition device can be built by using an electrical motor driving a Nipkow disk, a small box containing a single light-sensitive ( electric ) element and a conventional image focusing device ( lens, dark box, etc . ).
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The magnetic horn ( also known as the " Van der Meer horn " ) is a high-current, pulsed focusing device, invented by the Dutch physicist Simon van der Meer at CERN . It selects pions and focuses them into a sharp beam.
