Problem with GPRS frequency error

Hi guys,

Now I met a problem that GPRS freq. error larger than normal number
while result is normal for GSM or EGPRS operation.
Almost no changes on layout for this version of PCB compared to last version which passed this item.
Should this be RF or hardware issue ?
Data call or multistlot TX have nothing different from operation in EGPRS.
How comes ?

Thanks!

Hi Wilson_yu_chen,

You say "Almost no changes on layout for this version of PCB compared to last version which passed this item"

How about the component used in the board, especially x'tal or any things related in freq gen ? Is it's tolerance PPM (Part Per Million) meets the required spec ?

prd

Hi,

I use same chip as last version of PCB.
That TCXO spec:
Stability / Tolerance:
Tolerance after reflow 2ppm + stability over supply voltage+load 0.5ppm=2.5
AFC pulling: -16 ~ +16ppm
linearity: 20ppm (positive/negative)
Phase noise:
400Hz: -118 dBc/Hz
30KHz:-137 dBc/Hz
Start time little longer: 4.6ms

Will the tolerance requirement be different for GSM, GPRS, and EGPRS ?
Could you please specify the number ?

Hi,

The TCXO PPM should be indicated in your chipset datasheet.

Use the same software and same configuration to compare your reference design and this new version. Be careful, the software that work might not be the right one, some times misinitialized software may work well until new pcb version.

prs