how to broaden peaks of s11 and s22 in lna design
I am designing an LNA .While doing the impedence matching i get very narrow peaks of s11 and s22 .As a result of this s11 and s22 for the centre frequency comes below -10db but the whole bandwidth does not satisfy my requirement of s11 and s22 <-10db.
Can somebody tell me how to slighly broaden the peaks of s11 and s22 through matching network.I mean whether to add L or C in Parallel or series and why?
Hi I'd suggest to try to use slight shunt feedback - usually it helps to to broaden the frequency range where the amplifier is matched, but at the cost of degradation in noise figure and gain.
Also maybe you use ideal capacitors and inductors to perform matching - that's why you get very narrow bandwidth?
Real lossy elements increase the width of the band.[/img]
Use multiple stage matching circuit.I mean, broadband matching circuits provide more bandwidth.
For instance C-L-C or L-C-L etc.
thanks for your reply but i am already using a pie network of LCL...is this ok or i should go for something else.
Added after 4 minutes:
can u please tell me how to use shunt feedback.
LCL network has two poles and does not create a single notch.Either you have calculated wrong the component values or application has been poorly done..
Series RC-network which connects input and output of amplifier. The value of C should be such that its impedance is smaller than R at the frequency of interest.
Probably you use a high Q matching network, you should use a low Q matching network for wider bandwidth;
Try a more broadband matching network. Exploit the Q contours on the Smith chart to design a matching network that will provide the appropriate bandwidth. A useful freeware for this task is LLSmith fron RFDude.
Good Luck