GSM TXVCO loading problem

[Wilson_yu_chen]

Hi,

For GSM RF system.
I'm trying to investigate TXVCO loading unmatched to 50 Ohm problem.
Let me say, if here exists TXVCO output cascaded into RF power amplifier, what if
NOT 50 ohm load trace really happens.
If we temperarilly disregard varying input impedance at different output power level of PA, and make assumption of constant bias (impedance) seen from PA input. What would happen directly by this load ? AND what can I do to alleviate this
problem ?

What I can come out now by the impact is load pulling or frequency pushing. Some returned VCO power back to miss guarding the GSM phase and even frequency accuracy.

My temporarily strategy is to higher VCO bias to get more power input into PA, and
may bring substantially lower output phase noise or modulation spectrum. BUT
pulling effect may get worse ??
And also I'll try to widen loop bandwidth by Higher Kv and charge pump current to a allowable max value without introducing too much noise comes in loop.


Any body can correct me or have some comment on this ??

Thanks !!
wilson