Tripole to the rescue [antennas]

Whether it is the Palm VIIx handheld organizer or the VV Kyocera Smartphone, people love the freedom offered by the wireless connectivity of these gadgets. However, what the wireless service providers try to downplay is the low-speed Internet connection necessitated by the congested radio channels in the cellular/PCS bands. Several strategies are being tried to deal with this problem. The present paper discusses increasing the channel capacity in a scattering environment by using dual-polarized radio signals (Andrews et al. 2001). The extra capacity arises because there are six distinguishable electric and magnetic states of polarization at a given point, rather than two as is usually assumed. A set of three collocated orthogonal dipole antennas ("tripoles") at both the transmitting and receiving sites can triple the data rate. Andrews et al. used this approach to transmit an image of a Joan Mire painting, sending the red, green, and blue components of the picture simultaneously via three electric polarization states. If three magnetic-dipole antennas were added to the system, three additional information channels would become available because, in a scattering environment, the three magnetic-field components would be uncorrelated with one another as well as with the electric-field components.