How to make output matching wider?

[sarge]

Hi to all,

Currently, I'm designing simple LNA IC, which will work at 1565 - 1630 MHz frequency band. All with it is ok, except output matching - S22 has approximately 125 MHz bandwidth at level -10 dB.

This is first matching circuit which i have used:



The circuit is quite good, but value of series capacitor is very small and with corners and mismatches i'll get big changes in output matching.

Another circuit, that i have tried, is simple series inductance at output: with load LC network i can reach real 50 Ohm and with series inductance i cancel image part.

Both circuit have narrow bandwidth. Could you give me advice about the way to get wider output matching (target value ~ 200 MHz) ?

PS. I already tried to connect resistor in parallel with load inductor and lowering Q. This works, but cost for additional 20 MHz extension is -3 dB in a gain.

PPS. I can't place additional inductors - there are not enough space on chip

Thanks in advance.

 

[vfone]

Use a Pi match (two caps, and one inductor) which will give wider BW. Increasing the number of poles of the Pi network would increase the BW even further.