Antennas Get Smart; July 2003; Scientific American Magazine; by Martin Cooper; 8 Page(s)

Each of us is immersed in a sea of radio-frequency waves. The invisible electromagnetic energy comes from many sources: broadcast towers, cellular-phone networks and police radio transmissions, among others. Although this radiation may be harmless to our bodies, it can severely inhibit our ability to receive and transmit information. Excess radio energy is a kind of pollution, because it can disrupt useful communications. As the intensity of radio-frequency interference in our environment grows, we have to raise the volume of radio signals so that they can be heard over the electromagnetic background noise. And as our electronic communications become more intense, they simply add to the din of radio interference.

One solution to this problem lies in a new class of radio antennas that could dramatically reduce man-made interference. Instead of wastefully broadcasting personal communications-such as cell-phone calls-in all directions, these innovative antennas track the positions of mobile users and deliver radio signals directly to them. These antenna systems also maximize the reception of an individual cell-phone user's signal while minimizing the interference from other users. In effect, the antennas create a virtual wire extending to each mobile phone.