bode-fano limit

Hello all,
I use ADS Smith Chart tool to match using lumped elements (mainly L and C) .. but S11 reaches minimum in a verry narrow band of frequencies around the center frequency (Say 100MHz)...

Can i make binomial matching (wider band matching) with characteristics as shown in the attached figure using ADS? or generally with anyother tool, can someone help me about it?

I know that it's done by multiple sections of λ/4 transmission lines, but i'm asking, can this be done by LUMPED ELEMENTS (L and C) ?

Thanks in advance,
Ahmad,

you must learn something called the "fano limit", or sometimes the "bode-fano limit".

Well, can you guide me through them?
Also, for my original question, I wonder can it be done using lumped elements, or T.L. is a must?

Thanks,
Ahmad,

It doesn't matter if you use transmission lines or lumped elements, the matched bandwidth is restricted by the Fano limit. There were a couple of papers published in IEEE Antenna's magazine with some details on the limit within the past couple of years. The conclusion was that more than 2 or 3 sections was pointless.

Using the smith chart, you will tend to get a more broadband match if you keep the impedance trajectory towards the center. Also, If you add parasitic resistance to your elements, that will tend to make the match a bit more broadband, as you are de-q'ing the circuits.

Dave
www.keystoneradio.com

You can use a cascade of LC structures to improve the bandwidth of your matching. I usually don't use the ADS Smith Chart tool to match, but I do the S parameter simulation to match a load. You can use the optimizator also.

By

I want to learn how to use optimizer, can you give me a suitable turtorial for it?

thanks,
Ahmad,

Regarding matching network using lump elements. This is what i did in ADS in schematic, i try to design a LC network before a filter, as the filter was mismatch.

Port 1 (50Ω input) => LC network => filter (S2P data item) => port 2(50Ω output)

And i set goal such that the S11 will be less than, say -30 dB at the frequency range that i want to match. I optimize the L and C in order to meet the goal. However, it doesn't seem to match the filter at the input. Is there any wrong with my configuration, please correct me, as i also quite keen to know how to design matching lumped elements in ADS.

Thanks.