STB5600 Datasheet | STMicroelectronics

ESCRIPTION The STB5600, using STMicroelectronics HSB2, High Speed Bipolar technology, implements a Global Positioning System RF front-end. The chip provides down conversion from the GPS . (L1) signal at 1575 MHz via an IF of 20MHz to an output frequency of 4MHz suitable for ST20GP1 GPS processor. It uses a single external reference oscillator to generate both RF local oscillator signals and the processor reference clock. PIN CONNECTION (top view) Data Sh ee August 1998 1/10 . . Data Sheet 4 U . .. FUNCTIONAL DESCRIPTION The STB5600 GPS front-end is fed with the signal from an active antenna, via a ceramic RF filter. The gain between the antenna element and the STB5600 is expected to be between 10d B and 35d B overall, made up of the antenna LNA gain, the feeder loss, connector loss, and the ceramic filter loss. In order to use an off-the-shelf ceramic filter, conventionally 50 Ohms single ended, a matching circuit is used. (see appendix A.1), which provides a 300 Ohm differential drive to the STB5600. A similar circuit can be used to feed the LO signal if using the remended low-cost oscillator circuit (appendix A.3). Note that the STB5600 radio architecture and the oscillator described here are covered by various patents held by SGS-Thomson and by others. The use of the circuits described in this data-sheet for any other purpose may infringe such patents. - RF SECTION The differential input signal is amplified by the RF-Amp and mixed with the oscillator signal amplified from the LO+,LO- inputs to generate a balanced 20.46MHz IF signal. The LO buffer amplifier may be fed differential or single ended signals, at levels between -60d Bm and -20d Bm . - IF SECTION The 20MHz differential signal from the mixer is fed through an external LC filter to suppress undesirable signals and mixer products. The multi-stage high-sensitivity limiting amplifier is connected to a D-type latch clocked by an internally derived 16MHz clock.. The effect of sampling the 20MHz...