Re: GPS Receiver
as autor suggest, he use low if conversion for gps signal. important is, that for mixers he use, they don't need signal at RF input freq, but only half. that's mean, that there is low isolation request, becouse there is low signal injection to dc. also non direct conversion eliminate DC amplifier in IF section.
for IF preamplifier, you have to design with many, many filters (resistors and capacitors), becouse of high gain there is crosstalk between I and Q channel. if you touch the case of TO92 transistor somewhere from the start of the chain, you can hear clear signal in other. circuit is on one PCB but have a distance about 2 cm between (there is place for filters for power supply distribution, as you see, nearer the source you are, more isolation require
there were problems with LO too. for GPS you have to use very clean signal, i think that there is some 80dBc at 10KHz which is enought. you can also use worse oscilaltor, but, better the LO, better position
) latest amplifier with bfr91 is just for amplifying power becouse of thwo filters there (each has 4dB of loss :? ), these filters are for removing harmonics 100 Mhz appart and only a few dB under the main signal
design has some problems becouse high noise figure (8dB), and low gain at RF stage. it need at least 20-40dB more gain with well filtered signal. :twisted:
if you need more question for this ask me, becouse I know the author. he will continue design as soon as he will have time using spartan3, first verifying radio part with autocorrelation 8O
you can avoid building RF part as this: buy cheap commercial GPS receiver/module, and solder coax cable to last IF :twisted: be aware of capacitance of cable, you can alo solder cable to digitialized stream, find where to connect cable in datasheet of IC in RF section. the most cheap and simple solution if you wanna play with correlators.
for books how to make software part of GPS, author has references for some book also on elektroda
use search