In a mutually coupled antennaarray (notably a Yagi-Uda antenna), the driven element is the single antenna that has an applied source feed. The other antenna elements are not excited (or driven). There are a few reasons why one would only drive one element of the array. Doing this in the manner of a Yagi-Uda array allows for the field patterns to be directed in one direction with increased gain. The other elements are parasitic and take advantage of mutual coupling to aim the antenna.
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