 silicon allows us to make it smaller, cheaper, and much more widespread." Silicon is the ubiquitous element used in numerous electronic devices, including the microprocessor inside personal computers. It is the second most abundant element in the earth's crust (after oxygen), and components made of silicon are cheap to make and are widely manufactured. "In large volumes, it will only cost a few dollars to manufacture each of these radar chips," says Hajimiri. "The key is that we can integrate the whole system into one chip that can contain the entire high-frequency analog and high-speed signal process- ing at a low cost," he notes. "It's less powerful than the conventional radar used for aviation, but since we've put it on a single, inexpensive chip, we can have a large number of them, SO they can be ubiquitous." The chip also has several other telecom applications. For communications systems, the chip's ability to steer a beam allows it to provide a clear signal. Mobile phones, for example, radiate their signal omnidirectionally. That's what contributes to interference and clutter in the airwaves. "But with this tech- nology you can focus the beams in the desired direction instead of radiating power all over the place and creating additional interference," says Hajimiri. "At the same time you're maintaining a much higher speed and quality of service." The chip can also serve as a wireless, high-frequency communications link, providing a low-cost replacement for the optical fibers that are currently used for ultrafast communications. The chip runs at 24 GHz (24 billion cycles in one second), an extremely high speed, which makes it possible to transfer data wirelessly at speeds available only to the backbone of the Internet (the main network of connections that carry most of the traffic on the Internet). A small device based on the Caltech chip could, for example, be placed on the roof of a house or office building, replacing bulky satellite dishes or cable/DSL connections. 6.6.2 Train Monitor Cars, trucks, and b