about GPS front-end design?

[nj_jack]

gps front end design

I want to design a gps front-end to collect IF sampling data.
but i find gps receiver chip has usually two bits output sampling data, I wish to be able to find a chip whose IF(immediate frequency) is analoy output, thus i can obtain the data i want through ADC.
can you give me some advice?

 

[brmadhukar]

Hi,
Maxim has an RF that gives you analog output. If you are not working on the HP-GPS I suggest you avoid any analog output receiver. IT IS A PAIN IF YOU DO NOT GET PROPER COMPONENTS OR BOARD.
Hope this helps,
brm

 

[nj_jack]

HI, brmadhukar
can you tell me the chip type? I need it very much!
I want to try it, though I think your advice is very pertinent. hope your helps!

 

[bobxing]

Hi!

i am looking maxim RF-IC chips as well.

I know they develop 4 types
MAX2740,2741,2742,2745,
But it takes time to get since they are not quite common.

Please tell us if you can find it, thanks

 

[yifen]

You may also find the NEC 1007k, 1008k and 1009k GPS RF IC, too.

 

[bobxing]

Yes, I have heard about that NEC series, they are SiGe Process,
Maxim is RFCMOS.

 

[brmadhukar]

Hi,
From my experience,
Maxim was a pain designing with and the support was stopped after some time. (there was some revamping in MAXIM, but whatever the support I got it was excellent). You need to follow the exact recommended layout there was intefreernce of the refrence clock and required design of some odd filters. BUT IT WORKED.
Now I have stopped working on the RF side for time being. However I have heard that NEC is also quite difficult to work with.

B R M

 

[bobxing]

Thanks for your reply.

I know SONY's GPS does not contain AGC, but it is 1-bit ADC.

Speaking of AGC, which do you think better? AGC/PGA or limit amplifier???

thank you!

 

[brmadhukar]

Hi,

Limiters are not really useful except in case where a voltage surge is expected and in this case u need to use a limiter (at discrete level). For IC level I am not aware what is the cutoff they can provide.

I would still prefer AGC, for normal operation. How to do it in an analog front end is a bit difficult.

HOPE THIS HELPS.
Madhukar B R