Science Fair Projects Ideas - Driven element

All Science Fair Projects

      

Science Fair Project Encyclopedia for Schools!

  Search    Browse    Forum  Coach    Links    Editor    Help    Tell-a-Friend    Encyclopedia    Dictionary     

Science Fair Project Encyclopedia

For information on any area of science that interests you,
enter a keyword (eg. scientific method, molecule, cloud, carbohydrate etc.).
Or else, you can start by choosing any of the categories below.

Driven element

In a mutually coupled antenna array (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 resons 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. In a log periodic dipole array (LPDA), only one of the many dipoles is driven at a time. The dipole that is driven depends on the frequency of the signal. The advantage of this over an antenna such as a Yagi, which is only designed for one frequency, is that the antenna can be made relatively broadboand (nearly 2:1) by exciting differently sized elements that are resonant at different frequencies.

Note that when a "driven element" is referred to in an antenna array, it is assumed that other elements are not driven (i.e. parasitic) and that the array is tightly coupled (spacing far below a wavelength). It is also possible to have multile driven elements in an array. For example, a two element array spaced a quarter wavelength apart has a distinct cardioid pattern when the second element is driven with a source -90 degrees out of phase relative to the source of the first element.

10-26-2009 08:16:03
The contents of this article is licensed from www.wikipedia.org under the GNU Free Documentation License. Click here to see the transparent copy and copyright details
Science kits, science lessons, science toys, maths toys, hobby kits, science games and books - these are some of many products that can help give your kid an edge in their science fair projects, and develop a tremendous interest in the study of science. When shopping for a science kit or other supplies, make sure that you carefully review the features and quality of the products. Compare prices by going to several online stores. Read product reviews online or refer to magazines.

Start by looking for your science kit review or science toy review. Compare prices but remember, Price $ is not everything. Quality does matter.
Science Fair Coach
What do science fair judges look out for?
ScienceHound
Science Fair Projects for students of all ages
All Science Fair Projects.com Site
All Science Fair Projects Homepage
Search | Browse | Links | From-our-Editor | Books | Help | Contact | Privacy | Disclaimer | Copyright Notice