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Software-radio navigation receiver awaits Galileo

The first satellite for the European Galileo navigation systems has been launched: a usable constellation will become operational in 2008. With its SE4120 receiver chip, SiGe Semiconductor is enabling designers to create products that will be “Galileoready”. Using software-defined- radio techniques, SiGe says that it can make any necessary adaptations to the Galileo standard as it is finalised, and the company expects the combination of GPS and Galileo to enable a broad range of location-based products and services based on portable devices, through faster and more accurate position fixes in a wider variety of situations. SiGe believes that wider use in hand-held devices demands extra receiver performance in sensitivity and power. The company believes— in contrast to some providers who are aiming for single-chip implementations— that the receiver function is best partitioned into a separate RF chip. It has therefore designed the 4120L to interface to a baseband functional block that “anticipates” an SDR-type front end. That baseband awaits the finalisation of the Galileo specification, but with the 4120L you can now configure a GPS terminal that you can upgrade to Galileo by software. Its baseband interface provides I/Q or real outputs with programmable resolution. At the front end there is an on-chip LNA with 18 dB gain and a 1.6 dB noise figure; the company says that under controlled conditions, systems built with the chip will track satellite signals down to 170 dBm. The receiver includes a linear AGC, a multibit ADC and employs a low-IF architecture. Software-programmable filters adjust to 2.2 MHz bandwidth for GPS or 4.4 MHz for Galileo signals. The chip is sampling now, in a 4-mm2 24-lead package.

—by Graham Prophet
SiGe Semiconductor, www.sige.com.