wTo#head-6fb42901f5e11125848e5805ce715432a1d4cd20.Make sure to check out the "Build an Antenna Yourself" category, where you'll see antennas made from potato chip cans, sardine cans, and even Chinese cookware! The past decade or SO has brought a revolution in the way we communicate. The Internet and multimedia applications have fueled an enormous appetite for high-speed and high-bandwidth facilities, while mobile phones and other wireless devices have created a growing desire for ubiquitous connectivity for a large num- ber of subscribers. Needless to say, the near future must promise a new generation of wireless high-bit-rate devices. However, we have a basic obstacle to overcome: the relatively low bit rate that current wireless systems support, limited by the information capacity between a transmitter and a receiver. This information capac- ity is defined by the famous formula called Shannon's Law (discussed later in this chapter). With the overcrowded frequency spectrum and limitations on maximum power, we are challenged in how to increase the information capacity. Since 1996, multiantenna arrays have been suggested as a way to stretch the limit of Shannon's Law, making better use of the available spectrum and mitigating the effects of various impairments. It is increasingly clear that multiantenna tech- nology is going to play an essential role in the wireless communications of the future. These newer antenna approaches include phased-array antennas, magnetic polarization antennas, and MIMO antennas, which are all described in the follow- ing sections. Phased-Array Antennas The simplest multiantenna array is a phased-array antenna, also called a steered- beam antenna. Intelligent antennas based on phased-array technology can be used to mitigate the effects of multipath and other environmental interactions, such as proximity to metal. A phased-array antenna is usually implemented as a flat panel with a relatively large number of active antenna elements (see Figure 13.2). The elements can be electronically ste