GPS Receiver

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eng.

Joined: 15 Jul 2004
Posts: 43

18 Sep 2004 17:13 gps fpga

hi
i want to design a gps receiver ,i would appreciate any information on
how to implement it. which is better fpga or dsp?
thanks in advance

jayakumarjay

Joined: 18 Jun 2004
Posts: 23

19 Sep 2004 10:28 bfr91 receiver

wht information u need

did u need abt communication related gps

or asic related gps

eng.

Joined: 15 Jul 2004
Posts: 43

19 Sep 2004 17:40 fpga vs asic on gps receivers

which is better for the implementation,fpga or dsp? and if there is any
links that have information on that

javad

Joined: 18 Aug 2004
Posts: 55
Helped: 1

20 Sep 2004 8:35 buy hobby gps receiver

Dear friend,
You can design a gps receiver without using FPGA/ASIC. No ASIC or FPGA for correlator needed: low
cost, compact design and less weight!
You can do it on one DSP chip.
For example see below:
http://www.spiritcorp.com/16channel.html

Aser

Joined: 01 Jul 2004
Posts: 73
Helped: 5

20 Sep 2004 10:52 gps receiver by fpga

Some companies provide special chipsets for GPS
like Zarlink,Atmel, Motorola.
Such a chipset contains analog frontend, and
correlator with microprocessor.
If you awfully want to utilize the FPGA
you have to put that analog frontend,
FPGA, and microprocessor.
The microprocessor is preferrably with the floating point.
It can be PC as well.
Then FPGA can implement correlators that are controlled by
that microprocessor.

Mazi3

Joined: 29 May 2002
Posts: 101
Helped: 2
Location: Europe

23 Sep 2004 13:17 design gps receiver

you will find fpga gps project at h*t*t*p://w*w*w2.arnes.si/~mjanez6/delo/erk2003/gps_kaz.html

Smile

IceMan4

Joined: 13 Oct 2004
Posts: 10
Location: Jordan

13 Oct 2004 14:46 wht gps receiver do i have

Dear Mazi3,

I am interested in this topic, and thanks for the URL

But the problem that everything was written not in english

Can you help me to find english version of this project

Thanks

Mazi3

Joined: 29 May 2002
Posts: 101
Helped: 2
Location: Europe

20 Oct 2004 10:57 how to build gps receiver

i know that it is not in english, only in slovene, but you can find very good literature references there. they will be very helpfull becouse they are on ACTUALY building GPS receiver not only theory behind it Smile

as in many other literature

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20 Oct 2004 10:57 Ads

IceMan4

Joined: 13 Oct 2004
Posts: 10
Location: Jordan

20 Oct 2004 12:05 Re: GPS Receiver

Thank you for ur reply

This site contain a very good information as I see it

I will try to find a software translater to english so i can understand every thing

Thanks again

brmadhukar

Joined: 21 Jun 2002
Posts: 844
Helped: 29

20 Oct 2004 12:31 Re: GPS Receiver

Hi,
If you want to design your own GPS Rx use a FPGA + A powerful uC + RF for large volumes. For Fun/hobby you may replace the uC by a DSP. Remember memory matters.
B R M

IceMan4

Joined: 13 Oct 2004
Posts: 10
Location: Jordan

20 Oct 2004 12:39 Re: GPS Receiver

Hi again

For my hobby project, I do not have any problem in the uc (AT89c51) and the FPGA (Xilinx) But everything depends on the RF Stage that will convert the RF data to digital data

Do u have some references (Free one ) on the GPS theory and principles and about the Rf Stage?

Thanks

presto

Joined: 26 Nov 2001
Posts: 39

20 Oct 2004 12:48 Re: GPS Receiver

Here is the link for opensourceGPS

http://sourceforge.net/projects/osgps/

Mazi3

Joined: 29 May 2002
Posts: 101
Helped: 2
Location: Europe

25 Oct 2004 11:31 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 Smile

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 Smile

) latest amplifier with bfr91 is just for amplifying power becouse of thwo filters there (each has 4dB of loss Confused

), these filters are for removing harmonics 100 Mhz appart and only a few dB under the main signal Crying or Very sad

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 Evil

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 Shocked

you can avoid building RF part as this: buy cheap commercial GPS receiver/module, and solder coax cable to last IF Twisted Evil

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 Smile

use search Smile

sztibi82

Joined: 31 Aug 2004
Posts: 259
Helped: 5

25 Oct 2004 12:04 Re: GPS Receiver

Hi.
Are you from Romania. If yes, i suggest to buy the conexclub, in the last number a gps is presented.

The receiver is already done using a special receiver module whic is vailable in store.
it cost about 50 euros(I heard onlyi am not sure) in the book is mentionated as cheap methode to make it.