In-building wireless systems extend the coverage of unfettered communications networks within confined spaces. Because propagation of radio waves through concrete and metal is extremely lossy if at all possible, service providers rely on omnidirectional antennas such as the Ultrasphere in-building wireless antenna from Laird Technologies (St. Louis, MO) to stretch their coverage areas within shopping malls and office buildings. The beauty of the Ultrasphere is its size and dimensions: at only 179.2 x 80.4 x1.70 mm, it can be hidden almost anywhere within a structure while still providing fullsized RF performance.
The Ultrasphere model CAF 94895 antenna (see figure) offers a single solution for multiple wireless applications from 800 to 2400 MHz. It features a toroidal field pattern (with omnidirectional coverage in any plane around its long axis and two lobes in any plane parallel to the long axis) and provides as much as 3.6 dBi gain (depending on frequency) over that range; it replaces much larger omnidirectional antennas that usually offer a fraction of the frequency coverage. For example, a single CAF 94895 antenna can provide the following band coverage: AMPS (1.8 dBi gain from 806 to 896 MHz); GSM (1.6 dBi gain from 880 to 960 MHz); PCS (3.6 dBi gain from 1850 to 1990 MHz); DCS (2.2 dBi gain from 1710 t 1880 MHz); UMTS (2.9 dBi gain from 1920 to 2170 MHz); and ISM and Bluetooth (2.4 dBi gain from 2400 to 2500 MHz).
The rectangular-shaped antenna operates with linear polarization at characteristic impedance of 50 ohms. It can handle input power levels to 50 W, and connects to a communications system or network by means of an SMA female connector. It provides a good impedance match (depending upon frequency) to associated electronics with less than 2.50:1 VSWR for AMPS and GSM bands and less than 2.0:1 VSWR for all other bands. According to Craig Somach, director of business development for the Antenna Division of Laird Technologies, "By offering users a single device containing multiple antenna solutions, customers will purchase a product that enables an already installed future technology migration path."
The Ultrasphere model CAF 94895 antenna is ideal for in-building applications and communications networks where maintaining good performance with mobile users is important, and is targeted at cellular voice and data service providers, system integrators, original equipment manufacturers (OEMs), and communications equipment valueadded resellers (VARs). It is supplied by a company that is hardly a " household" name in antenna technology, Laird Technologies (www.lairdtech.com). But Laird is a well-managed global supplier of not just antennas but thermal control materials and electromagneticinterference (EMI) control materials. The firm added to its antenna capabilities in 2004 with the acquisition of well-known antenna provider Centurion Wireless Technologies. P&A: $34.95 (500 qty.); stock. Laird Technologies, 3481 Rider Trail South, St. Louis, MO 63045; (800) 843-4556, e-mail: firstname.lastname@example.org, Internet: www.lairdtech.com.