1. Field of the Invention
The present invention relates generally to Global Positioning System (GPS) receivers, and in particular, to a method and apparatus for a single local oscillator (LO) frequency band to receive dual-band signals.
2. Description of the Related Art
The use of GPS in consumer products has become commonplace. Hand-held devices used for mountaineering, automobile navigation systems, and GPS for use with cellular telephones are just a few examples of consumer products using GPS technology.
GPS-enabled devices, such as cellular telephones, have also been introduced into the consumer marketplace. These devices allow for the use of Location-Based Services (LBS) which are services, advertisements, and other features that are offered based on the location of the user. As such, GPS-enabled devices are used worldwide.
The use of the frequency spectrum in the United States is very tightly controlled by the government. However, several bands are in use for GPS, and other bands are used for devices that are used with GPS devices, such as cellular phones and Personal Data Assistants (PDAs). Thus, these devices, which are usually battery powered, must power both the GPS portion of the device and the other portion of the device, whether it is a cell phone or other electronic device.
Electronic devices usually use local oscillators (LO), for clocks or for downconversion processes. These LO components usually draw power, and usually are designed for a single frequency downconversion. However, when multiple functions are present in the same device, multiple LO components are typically used, since the devices are not designed with a single LO frequency plan in mind.
It can be seen, then, that there is a need in the art to make GPS-enabled devices with Local Oscillators capable of handling more than one frequency downconversion.