GSM out-band blocking ?

[Wilson_yu_chen]

Hi guys,

Currentl I use receive FEM with matching differential can have
850 band RF receive harmonics generally failure, meaning, failing on
2nd, 3rd, 4th, 5th, 6th, 7th harmonics blocker frequency witj total
number of exceptions = 23 ~27. >24.

My matching topology is series capacitor with shunt inductor, and
exceptions get better to be 10 when topolopy changes to series inductor.

My PA with its VBAT capacitor is near matching components. I'm wandering
if any factor can get down the harmonics if no changing of topology.
My layout weakness is no much chance to put multiple vias along RX paths.

1. VCO supply RF choke ?
2. PA big capacitor removal ?

Please help !!

Regards, wilson

 

[eecly]

Have you tried to place bandpass filter?

 

[Wilson_yu_chen]

Not allowed, because I use RX font-end module with SAW filter included.

Thanks!