Active receiving antennas for automotive applications

The Global Positioning System (GPS) provides an affordable worldwide radio navigation capability. However, in a city, where high-rise buildings can block out the satellite signal, navigation has to be supplemented by ground transmitters. By combining a GPS receiver with a wireless communications link, an automatic vehicle location system can be effectively set up. As for satellite radio services, near CD quality music is beamed from a satellite to automobile radio receivers, and this, too, has to be supplemented by ground repeaters for listeners passing through urban areas. Common to these applications is an antenna module that has two antenna elements, namely, a circularly polarized (CP) antenna for receiving satellite signals and a linearly polarized (LP) antenna for terrestrial signals. The CP antenna of each module is integrated with a low-noise amplifier, making it an active antenna. Two active receiving antenna modules are presented. The first module consists of a GPS CP antenna operating at 1.57342-1.57742 GHz and a GSM LP antenna at 880-960 MHz for automotive navigation. The second module consists of a CP and an LP antenna, both operating at 2.3285-2.3485 GHz for satellite radio services.