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Measurements >> RF Measurements >> S11 of the Front-end
https://designers-guide.org/forum/YaBB.pl?num=1236027683

Message started by YYou on Mar 2^nd, 2009, 1:01pm

Title: S11 of the Front-end
Post by YYou on Mar 2^nd, 2009, 1:01pm

Dear all,

I am testing my front-end. With off-chip matching components, the input can be matched at the operating frequency. But at the same time I always see another notch at twice the operating frequency, which is not there in simulation.

Can anyone give some suggestions how this could happen ?

Thanks so much ,

Yyou

Title: Re: S11 of the Front-end
Post by YYou on Mar 2^nd, 2009, 2:18pm

Just add some basic information:
1. the LNA is single-ended.
2. The matching is through inductive-degenerated structure.
3. Gate inductor is implemented off-chip.

Thanks,

Yyou

Title: Re: S11 of the Front-end
Post by pancho_hideboo on Mar 2^nd, 2009, 8:03pm

YYou wrote on Mar 2^nd, 2009, 1:01pm:

I am testing my front-end. With off-chip matching components, the input can be matched at the operating frequency.
But at the same time I always see another notch at twice the operating frequency, which is not there in simulation.
Can anyone give some suggestions how this could happen ?

Maybe due to parasitic effects of board and package.

Show me smith charts of input impedance with off-chip matching and without off-chip matching.