Multi-band mobile telephone antennas

This paper presents several designs of vehicle-installed antennas suitable for GSM-DCS-UMTS mobile telephone applications. One requirement is for a good impedance match across the bands, 7% at 925 MHz (890-960 MHz), 10% at 1800 MHz (1710-1880 MHz) and 12.5% at UMTS (1920-2175 MHz) and this presents considerable difficulties for many antenna structures. In each case the antennas are fed by a single coaxial feeder unlike many other designs previously reported which have separate feed points for each band. All the above types must meet certain radiation characteristics. The most important are omnidirectional azimuth coverage, high efficiency and high bandwidth. All the above antennas are very sensitive to external conditions (human body proximity, weather) and dependent on the mounting area (in-car, rooftop)