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To: JohnG who wrote (33299)	6/26/1999 10:11:00 AM
From: Clarksterh	Read Replies (3) \| Respond to of 152472

John - Fractal antenna--what is it? First, a fractal shape is one that has features of every length. The classic example is that if you measure the distance of geologic borders, the total length that you get depends, counter intuitively, on the size of the ruler. For instance, take a compass (one of those things that you used to draw circles with in high school) and measure the length of the Australian coast by sticking the point in at one spot and then rotating the other point until it hits the coast. Repeat from this new point. If the compass is 1 mile, then you might get 50,000 miles (i.e. you rotated the compass 50,000 times), but when you shrink the compass to 1/2 mile it goes up to 70,000 miles (i.e. you rotated the compass 140,000 times) and 1/4 mile would be 98,000 miles, ... . This really does happen in real life and it is why you often see measurements of the same geologic features which are wildly different. Note that most man made objects are not fractal. As you use smaller and smaller compass settings the length of the border approaches ever closer to a certain number. So, what is a fractal antenna? It is an antenna that is fractal in shape. The classic fractal antenna is a twisted cross within cross within cross within cross, ... . Since it has elements of every length it allows oscillation at every frequency (the whole point of an antenna is to allow oscillation at the transmit and receive frequencies) and thus works across a much wider range of frequencies than ordinary antennas which are not fractal and have elements of only at a few discrete lengths. NASA and others having been working on this for several years now. More than you wanted to know? Clark